text: 'use strict';
  
  //const canvas = document.getElementsByTagName('canvas')[0];
  const canvas =document.getElementById('cc'); 
  resizeCanvas();
  
  let config = {
      SIM_RESOLUTION: 128,
      DYE_RESOLUTION: 1024,
      CAPTURE_RESOLUTION: 512,
      DENSITY_DISSIPATION: 1,
      VELOCITY_DISSIPATION: 0.2,
      PRESSURE: 0.8,
      PRESSURE_ITERATIONS: 20,
      CURL: 30,
      SPLAT_RADIUS: 0.25,
      SPLAT_FORCE: 6000,
      SHADING: true,
      COLORFUL: true,
      COLOR_UPDATE_SPEED: 10,
      PAUSED: false,
      BACK_COLOR: { r: 0, g: 0, b: 0 },
      TRANSPARENT: false,
      BLOOM: true,
      BLOOM_ITERATIONS: 8,
      BLOOM_RESOLUTION: 256,
      BLOOM_INTENSITY: 0.8,
      BLOOM_THRESHOLD: 0.6,
      BLOOM_SOFT_KNEE: 0.7,
      SUNRAYS: true,
      SUNRAYS_RESOLUTION: 196,
      SUNRAYS_WEIGHT: 1.0,
  }
  
  function pointerPrototype () {
      this.id = -1;
      this.texcoordX = 0;
      this.texcoordY = 0;
      this.prevTexcoordX = 0;
      this.prevTexcoordY = 0;
      this.deltaX = 0;
      this.deltaY = 0;
      this.down = false;
      this.moved = false;
      this.color = [30, 0, 300];
  }
  
  let pointers = [];
  let splatStack = [];
  let bloomFramebuffers = [];
  pointers.push(new pointerPrototype());
  
  const { gl, ext } = getWebGLContext(canvas);
  
  if (isMobile()) {
      config.DYE_RESOLUTION = 512;
  }
  if (!ext.supportLinearFiltering) {
      config.DYE_RESOLUTION = 512;
      config.SHADING = false;
      config.BLOOM = false;
      config.SUNRAYS = false;
  }
  
  startGUI();
  
  function getWebGLContext (canvas) {
      const params = { alpha: true, depth: false, stencil: false, antialias: false, preserveDrawingBuffer: false };
  
      let gl = canvas.getContext('webgl2', params);
      const isWebGL2 = !!gl;
      if (!isWebGL2){
          gl = canvas.getContext('webgl', params) || canvas.getContext('experimental-webgl', params);
      }
  
      let halfFloat;
      let supportLinearFiltering;
      if (isWebGL2) {
          gl.getExtension('EXT_color_buffer_float');
          supportLinearFiltering = gl.getExtension('OES_texture_float_linear');
      } else {
  
          halfFloat = gl.getExtension('OES_texture_half_float');
          supportLinearFiltering = gl.getExtension('OES_texture_half_float_linear');
      }
  
      gl.clearColor(0.0, 0.0, 0.0, 1.0);
  
      const halfFloatTexType = isWebGL2 ? gl.HALF_FLOAT : halfFloat.HALF_FLOAT_OES;
      let formatRGBA;
      let formatRG;
      let formatR;
  
      if (isWebGL2)
      {
          formatRGBA = getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, halfFloatTexType);
          formatRG = getSupportedFormat(gl, gl.RG16F, gl.RG, halfFloatTexType);
          formatR = getSupportedFormat(gl, gl.R16F, gl.RED, halfFloatTexType);
      }
      else
      {
          formatRGBA = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
          formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
          formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
      }
  
      ga('send', 'event', isWebGL2 ? 'webgl2' : 'webgl', formatRGBA == null ? 'not supported' : 'supported');
  
      return {
          gl,
          ext: {
              formatRGBA,
              formatRG,
              formatR,
              halfFloatTexType,
              supportLinearFiltering
          }
      };
  }
  
  function getSupportedFormat (gl, internalFormat, format, type)
  {
      if (!supportRenderTextureFormat(gl, internalFormat, format, type))
      {
          switch (internalFormat)
          {
              case gl.R16F:
                  return getSupportedFormat(gl, gl.RG16F, gl.RG, type);
              case gl.RG16F:
                  return getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, type);
              default:
                  return null;
          }
      }
  
      return {
          internalFormat,
          format
      }
  }
  
  function supportRenderTextureFormat (gl, internalFormat, format, type) {
      let texture = gl.createTexture();
      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
      gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, 4, 4, 0, format, type, null);
  
      let fbo = gl.createFramebuffer();
      gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
      gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
  
      const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
      return status == gl.FRAMEBUFFER_COMPLETE;
  }
  
  function startGUI () {
      var gui = new dat.GUI({ width: 300 });
      gui.add(config, 'DYE_RESOLUTION', { 'high': 1024, 'medium': 512, 'low': 256, 'very low': 128 }).name('quality').onFinishChange(initFramebuffers);
      gui.add(config, 'SIM_RESOLUTION', { '32': 32, '64': 64, '128': 128, '256': 256 }).name('sim resolution').onFinishChange(initFramebuffers);
      gui.add(config, 'DENSITY_DISSIPATION', 0, 4.0).name('density diffusion');
      gui.add(config, 'VELOCITY_DISSIPATION', 0, 4.0).name('velocity diffusion');
      gui.add(config, 'PRESSURE', 0.0, 1.0).name('pressure');
      gui.add(config, 'CURL', 0, 50).name('vorticity').step(1);
      gui.add(config, 'SPLAT_RADIUS', 0.01, 1.0).name('splat radius');
      gui.add(config, 'SHADING').name('shading').onFinishChange(updateKeywords);
      gui.add(config, 'COLORFUL').name('colorful');
      gui.add(config, 'PAUSED').name('paused').listen();
  
      gui.add({ fun: () => {
          splatStack.push(parseInt(Math.random() * 20) + 5);
      } }, 'fun').name('Random splats');
  
      let bloomFolder = gui.addFolder('Bloom');
      bloomFolder.add(config, 'BLOOM').name('enabled').onFinishChange(updateKeywords);
      bloomFolder.add(config, 'BLOOM_INTENSITY', 0.1, 2.0).name('intensity');
      bloomFolder.add(config, 'BLOOM_THRESHOLD', 0.0, 1.0).name('threshold');
  
      let sunraysFolder = gui.addFolder('Sunrays');
      sunraysFolder.add(config, 'SUNRAYS').name('enabled').onFinishChange(updateKeywords);
      sunraysFolder.add(config, 'SUNRAYS_WEIGHT', 0.3, 1.0).name('weight');
  
      let captureFolder = gui.addFolder('Capture');
      captureFolder.addColor(config, 'BACK_COLOR').name('background color');
      captureFolder.add(config, 'TRANSPARENT').name('transparent');
      captureFolder.add({ fun: captureScreenshot }, 'fun').name('take screenshot');
  
      let github = gui.add({ fun : () => {
          window.open('https://github.com/Arshiamidos');
          ga('send', 'event', 'link button', 'github');
      } }, 'fun').name('https://arshiamidos.github.io');
      github.__li.className = 'cr function bigFont';
      github.__li.style.borderLeft = '3px solid #8C8C8C';
      let githubIcon = document.createElement('span');
      github.domElement.parentElement.appendChild(githubIcon);
      githubIcon.className = 'icon github';
  
      if (isMobile())
          gui.close();
  }
  
  function isMobile () {
      return /Mobi|Android/i.test(navigator.userAgent);
  }
  
  function captureScreenshot () {
      let res = getResolution(config.CAPTURE_RESOLUTION);
      let target = createFBO(res.width, res.height, ext.formatRGBA.internalFormat, ext.formatRGBA.format, ext.halfFloatTexType, gl.NEAREST);
      render(target);
  
      let texture = framebufferToTexture(target);
      texture = normalizeTexture(texture, target.width, target.height);
  
      let captureCanvas = textureToCanvas(texture, target.width, target.height);
      let datauri = captureCanvas.toDataURL();
      downloadURI('fluid.png', datauri);
      URL.revokeObjectURL(datauri);
  }
  
  function framebufferToTexture (target) {
      gl.bindFramebuffer(gl.FRAMEBUFFER, target.fbo);
      let length = target.width * target.height * 4;
      let texture = new Float32Array(length);
      gl.readPixels(0, 0, target.width, target.height, gl.RGBA, gl.FLOAT, texture);
      return texture;
  }
  
  function normalizeTexture (texture, width, height) {
      let result = new Uint8Array(texture.length);
      let id = 0;
      for (let i = height - 1; i >= 0; i--) {
          for (let j = 0; j < width; j++) {
              let nid = i * width * 4 + j * 4;
              result[nid + 0] = clamp01(texture[id + 0]) * 255;
              result[nid + 1] = clamp01(texture[id + 1]) * 255;
              result[nid + 2] = clamp01(texture[id + 2]) * 255;
              result[nid + 3] = clamp01(texture[id + 3]) * 255;
              id += 4;
          }
      }
      return result;
  }
  
  function clamp01 (input) {
      return Math.min(Math.max(input, 0), 1);
  }
  
  function textureToCanvas (texture, width, height) {
      let captureCanvas = document.createElement('canvas');
      let ctx = captureCanvas.getContext('2d');
      captureCanvas.width = width;
      captureCanvas.height = height;
  
      let imageData = ctx.createImageData(width, height);
      imageData.data.set(texture);
      ctx.putImageData(imageData, 0, 0);
  
      return captureCanvas;
  }
  
  function downloadURI (filename, uri) {
      let link = document.createElement('a');
      link.download = filename;
      link.href = uri;
      document.body.appendChild(link);
      link.click();
      document.body.removeChild(link);
  }
  
  class Material {
      constructor (vertexShader, fragmentShaderSource) {
          this.vertexShader = vertexShader;
          this.fragmentShaderSource = fragmentShaderSource;
          this.programs = [];
          this.activeProgram = null;
          this.uniforms = [];
      }
  
      setKeywords (keywords) {
          let hash = 0;
          for (let i = 0; i < keywords.length; i++)
              hash += hashCode(keywords[i]);
  
          let program = this.programs[hash];
          if (program == null)
          {
              let fragmentShader = compileShader(gl.FRAGMENT_SHADER, this.fragmentShaderSource, keywords);
              program = createProgram(this.vertexShader, fragmentShader);
              this.programs[hash] = program;
          }
  
          if (program == this.activeProgram) return;
  
          this.uniforms = getUniforms(program);
          this.activeProgram = program;
      }
  
      bind () {
          gl.useProgram(this.activeProgram);
      }
  }
  
  class Program {
      constructor (vertexShader, fragmentShader) {
          this.uniforms = {};
          this.program = createProgram(vertexShader, fragmentShader);
          this.uniforms = getUniforms(this.program);
      }
  
      bind () {
          gl.useProgram(this.program);
      }
  }
  
  function createProgram (vertexShader, fragmentShader) {
      let program = gl.createProgram();
      gl.attachShader(program, vertexShader);
      gl.attachShader(program, fragmentShader);
      gl.linkProgram(program);
  
      if (!gl.getProgramParameter(program, gl.LINK_STATUS))
          throw gl.getProgramInfoLog(program);
  
      return program;
  }
  
  function getUniforms (program) {
      let uniforms = [];
      let uniformCount = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
      for (let i = 0; i < uniformCount; i++) {
          let uniformName = gl.getActiveUniform(program, i).name;
          uniforms[uniformName] = gl.getUniformLocation(program, uniformName);
      }
      return uniforms;
  }
  
  function compileShader (type, source, keywords) {
      source = addKeywords(source, keywords);
  
      const shader = gl.createShader(type);
      gl.shaderSource(shader, source);
      gl.compileShader(shader);
  
      if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
          throw gl.getShaderInfoLog(shader);
  
      return shader;
  };
  
  function addKeywords (source, keywords) {
      if (keywords == null) return source;
      let keywordsString = '';
      keywords.forEach(keyword => {
          keywordsString += '#define ' + keyword + '\n';
      });
      return keywordsString + source;
  }
  
  const baseVertexShader = compileShader(gl.VERTEX_SHADER, `
      precision highp float;
  
      attribute vec2 aPosition;
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform vec2 texelSize;
  
      void main () {
          vUv = aPosition * 0.5 + 0.5;
          vL = vUv - vec2(texelSize.x, 0.0);
          vR = vUv + vec2(texelSize.x, 0.0);
          vT = vUv + vec2(0.0, texelSize.y);
          vB = vUv - vec2(0.0, texelSize.y);
          gl_Position = vec4(aPosition, 0.0, 1.0);
      }
  `);
  
  const blurVertexShader = compileShader(gl.VERTEX_SHADER, `
      precision highp float;
  
      attribute vec2 aPosition;
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      uniform vec2 texelSize;
  
      void main () {
          vUv = aPosition * 0.5 + 0.5;
          float offset = 1.33333333;
          vL = vUv - texelSize * offset;
          vR = vUv + texelSize * offset;
          gl_Position = vec4(aPosition, 0.0, 1.0);
      }
  `);
  
  const blurShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      uniform sampler2D uTexture;
  
      void main () {
          vec4 sum = texture2D(uTexture, vUv) * 0.29411764;
          sum += texture2D(uTexture, vL) * 0.35294117;
          sum += texture2D(uTexture, vR) * 0.35294117;
          gl_FragColor = sum;
      }
  `);
  
  const copyShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      uniform sampler2D uTexture;
  
      void main () {
          gl_FragColor = texture2D(uTexture, vUv);
      }
  `);
  
  const clearShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      uniform sampler2D uTexture;
      uniform float value;
  
      void main () {
          gl_FragColor = value * texture2D(uTexture, vUv);
      }
  `);
  
  const colorShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
  
      uniform vec4 color;
  
      void main () {
          gl_FragColor = color;
      }
  `);
  
  const checkerboardShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uTexture;
      uniform float aspectRatio;
  
      #define SCALE 25.0
  
      void main () {
          vec2 uv = floor(vUv * SCALE * vec2(aspectRatio, 1.0));
          float v = mod(uv.x + uv.y, 2.0);
          v = v * 0.1 + 0.8;
          gl_FragColor = vec4(vec3(v), 1.0);
      }
  `);
  
  const displayShaderSource = `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uTexture;
      uniform sampler2D uBloom;
      uniform sampler2D uSunrays;
      uniform sampler2D uDithering;
      uniform vec2 ditherScale;
      uniform vec2 texelSize;
  
      vec3 linearToGamma (vec3 color) {
          color = max(color, vec3(0));
          return max(1.055 * pow(color, vec3(0.416666667)) - 0.055, vec3(0));
      }
  
      void main () {
          vec3 c = texture2D(uTexture, vUv).rgb;
  
      #ifdef SHADING
          vec3 lc = texture2D(uTexture, vL).rgb;
          vec3 rc = texture2D(uTexture, vR).rgb;
          vec3 tc = texture2D(uTexture, vT).rgb;
          vec3 bc = texture2D(uTexture, vB).rgb;
  
          float dx = length(rc) - length(lc);
          float dy = length(tc) - length(bc);
  
          vec3 n = normalize(vec3(dx, dy, length(texelSize)));
          vec3 l = vec3(0.0, 0.0, 1.0);
  
          float diffuse = clamp(dot(n, l) + 0.7, 0.7, 1.0);
          c *= diffuse;
      #endif
  
      #ifdef BLOOM
          vec3 bloom = texture2D(uBloom, vUv).rgb;
      #endif
  
      #ifdef SUNRAYS
          float sunrays = texture2D(uSunrays, vUv).r;
          c *= sunrays;
      #ifdef BLOOM
          bloom *= sunrays;
      #endif
      #endif
  
      #ifdef BLOOM
          float noise = texture2D(uDithering, vUv * ditherScale).r;
          noise = noise * 2.0 - 1.0;
          bloom += noise / 255.0;
          bloom = linearToGamma(bloom);
          c += bloom;
      #endif
  
          float a = max(c.r, max(c.g, c.b));
          gl_FragColor = vec4(c, a);
      }
  `;
  
  const bloomPrefilterShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uTexture;
      uniform vec3 curve;
      uniform float threshold;
  
      void main () {
          vec3 c = texture2D(uTexture, vUv).rgb;
          float br = max(c.r, max(c.g, c.b));
          float rq = clamp(br - curve.x, 0.0, curve.y);
          rq = curve.z * rq * rq;
          c *= max(rq, br - threshold) / max(br, 0.0001);
          gl_FragColor = vec4(c, 0.0);
      }
  `);
  
  const bloomBlurShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uTexture;
  
      void main () {
          vec4 sum = vec4(0.0);
          sum += texture2D(uTexture, vL);
          sum += texture2D(uTexture, vR);
          sum += texture2D(uTexture, vT);
          sum += texture2D(uTexture, vB);
          sum *= 0.25;
          gl_FragColor = sum;
      }
  `);
  
  const bloomFinalShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uTexture;
      uniform float intensity;
  
      void main () {
          vec4 sum = vec4(0.0);
          sum += texture2D(uTexture, vL);
          sum += texture2D(uTexture, vR);
          sum += texture2D(uTexture, vT);
          sum += texture2D(uTexture, vB);
          sum *= 0.25;
          gl_FragColor = sum * intensity;
      }
  `);
  
  const sunraysMaskShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uTexture;
  
      void main () {
          vec4 c = texture2D(uTexture, vUv);
          float br = max(c.r, max(c.g, c.b));
          c.a = 1.0 - min(max(br * 20.0, 0.0), 0.8);
          gl_FragColor = c;
      }
  `);
  
  const sunraysShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uTexture;
      uniform float weight;
  
      #define ITERATIONS 16
  
      void main () {
          float Density = 0.3;
          float Decay = 0.95;
          float Exposure = 0.7;
  
          vec2 coord = vUv;
          vec2 dir = vUv - 0.5;
  
          dir *= 1.0 / float(ITERATIONS) * Density;
          float illuminationDecay = 1.0;
  
          float color = texture2D(uTexture, vUv).a;
  
          for (int i = 0; i < ITERATIONS; i++)
          {
              coord -= dir;
              float col = texture2D(uTexture, coord).a;
              color += col * illuminationDecay * weight;
              illuminationDecay *= Decay;
          }
  
          gl_FragColor = vec4(color * Exposure, 0.0, 0.0, 1.0);
      }
  `);
  
  const splatShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uTarget;
      uniform float aspectRatio;
      uniform vec3 color;
      uniform vec2 point;
      uniform float radius;
  
      void main () {
          vec2 p = vUv - point.xy;
          p.x *= aspectRatio;
          vec3 splat = exp(-dot(p, p) / radius) * color;
          vec3 base = texture2D(uTarget, vUv).xyz;
          gl_FragColor = vec4(base + splat, 1.0);
      }
  `);
  
  const advectionShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      uniform sampler2D uVelocity;
      uniform sampler2D uSource;
      uniform vec2 texelSize;
      uniform vec2 dyeTexelSize;
      uniform float dt;
      uniform float dissipation;
  
      vec4 bilerp (sampler2D sam, vec2 uv, vec2 tsize) {
          vec2 st = uv / tsize - 0.5;
  
          vec2 iuv = floor(st);
          vec2 fuv = fract(st);
  
          vec4 a = texture2D(sam, (iuv + vec2(0.5, 0.5)) * tsize);
          vec4 b = texture2D(sam, (iuv + vec2(1.5, 0.5)) * tsize);
          vec4 c = texture2D(sam, (iuv + vec2(0.5, 1.5)) * tsize);
          vec4 d = texture2D(sam, (iuv + vec2(1.5, 1.5)) * tsize);
  
          return mix(mix(a, b, fuv.x), mix(c, d, fuv.x), fuv.y);
      }
  
      void main () {
      #ifdef MANUAL_FILTERING
          vec2 coord = vUv - dt * bilerp(uVelocity, vUv, texelSize).xy * texelSize;
          vec4 result = bilerp(uSource, coord, dyeTexelSize);
      #else
          vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;
          vec4 result = texture2D(uSource, coord);
      #endif
          float decay = 1.0 + dissipation * dt;
          gl_FragColor = result / decay;
      }`,
      ext.supportLinearFiltering ? null : ['MANUAL_FILTERING']
  );
  
  const divergenceShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uVelocity;
  
      void main () {
          float L = texture2D(uVelocity, vL).x;
          float R = texture2D(uVelocity, vR).x;
          float T = texture2D(uVelocity, vT).y;
          float B = texture2D(uVelocity, vB).y;
  
          vec2 C = texture2D(uVelocity, vUv).xy;
          if (vL.x < 0.0) { L = -C.x; }
          if (vR.x > 1.0) { R = -C.x; }
          if (vT.y > 1.0) { T = -C.y; }
          if (vB.y < 0.0) { B = -C.y; }
  
          float div = 0.5 * (R - L + T - B);
          gl_FragColor = vec4(div, 0.0, 0.0, 1.0);
      }
  `);
  
  const curlShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uVelocity;
  
      void main () {
          float L = texture2D(uVelocity, vL).y;
          float R = texture2D(uVelocity, vR).y;
          float T = texture2D(uVelocity, vT).x;
          float B = texture2D(uVelocity, vB).x;
          float vorticity = R - L - T + B;
          gl_FragColor = vec4(0.5 * vorticity, 0.0, 0.0, 1.0);
      }
  `);
  
  const vorticityShader = compileShader(gl.FRAGMENT_SHADER, `
      precision highp float;
      precision highp sampler2D;
  
      varying vec2 vUv;
      varying vec2 vL;
      varying vec2 vR;
      varying vec2 vT;
      varying vec2 vB;
      uniform sampler2D uVelocity;
      uniform sampler2D uCurl;
      uniform float curl;
      uniform float dt;
  
      void main () {
          float L = texture2D(uCurl, vL).x;
          float R = texture2D(uCurl, vR).x;
          float T = texture2D(uCurl, vT).x;
          float B = texture2D(uCurl, vB).x;
          float C = texture2D(uCurl, vUv).x;
  
          vec2 force = 0.5 * vec2(abs(T) - abs(B), abs(R) - abs(L));
          force /= length(force) + 0.0001;
          force *= curl * C;
          force.y *= -1.0;
  
          vec2 vel = texture2D(uVelocity, vUv).xy;
          gl_FragColor = vec4(vel + force * dt, 0.0, 1.0);
      }
  `);
  
  const pressureShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uPressure;
      uniform sampler2D uDivergence;
  
      void main () {
          float L = texture2D(uPressure, vL).x;
          float R = texture2D(uPressure, vR).x;
          float T = texture2D(uPressure, vT).x;
          float B = texture2D(uPressure, vB).x;
          float C = texture2D(uPressure, vUv).x;
          float divergence = texture2D(uDivergence, vUv).x;
          float pressure = (L + R + B + T - divergence) * 0.25;
          gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);
      }
  `);
  
  const gradientSubtractShader = compileShader(gl.FRAGMENT_SHADER, `
      precision mediump float;
      precision mediump sampler2D;
  
      varying highp vec2 vUv;
      varying highp vec2 vL;
      varying highp vec2 vR;
      varying highp vec2 vT;
      varying highp vec2 vB;
      uniform sampler2D uPressure;
      uniform sampler2D uVelocity;
  
      void main () {
          float L = texture2D(uPressure, vL).x;
          float R = texture2D(uPressure, vR).x;
          float T = texture2D(uPressure, vT).x;
          float B = texture2D(uPressure, vB).x;
          vec2 velocity = texture2D(uVelocity, vUv).xy;
          velocity.xy -= vec2(R - L, T - B);
          gl_FragColor = vec4(velocity, 0.0, 1.0);
      }
  `);
  
  const blit = (() => {
      gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]), gl.STATIC_DRAW);
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
      gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 0, 2, 3]), gl.STATIC_DRAW);
      gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
      gl.enableVertexAttribArray(0);
  
      return (destination) => {
          gl.bindFramebuffer(gl.FRAMEBUFFER, destination);
          gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
      }
  })();
  
  let dye;
  let velocity;
  let divergence;
  let curl;
  let pressure;
  let bloom;
  let sunrays;
  let sunraysTemp;
  
  let ditheringTexture = createTextureAsync('LDR_LLL1_0.png');
  
  const blurProgram            = new Program(blurVertexShader, blurShader);
  const copyProgram            = new Program(baseVertexShader, copyShader);
  const clearProgram           = new Program(baseVertexShader, clearShader);
  const colorProgram           = new Program(baseVertexShader, colorShader);
  const checkerboardProgram    = new Program(baseVertexShader, checkerboardShader);
  const bloomPrefilterProgram  = new Program(baseVertexShader, bloomPrefilterShader);
  const bloomBlurProgram       = new Program(baseVertexShader, bloomBlurShader);
  const bloomFinalProgram      = new Program(baseVertexShader, bloomFinalShader);
  const sunraysMaskProgram     = new Program(baseVertexShader, sunraysMaskShader);
  const sunraysProgram         = new Program(baseVertexShader, sunraysShader);
  const splatProgram           = new Program(baseVertexShader, splatShader);
  const advectionProgram       = new Program(baseVertexShader, advectionShader);
  const divergenceProgram      = new Program(baseVertexShader, divergenceShader);
  const curlProgram            = new Program(baseVertexShader, curlShader);
  const vorticityProgram       = new Program(baseVertexShader, vorticityShader);
  const pressureProgram        = new Program(baseVertexShader, pressureShader);
  const gradienSubtractProgram = new Program(baseVertexShader, gradientSubtractShader);
  
  const displayMaterial = new Material(baseVertexShader, displayShaderSource);
  
  function initFramebuffers () {
      let simRes = getResolution(config.SIM_RESOLUTION);
      let dyeRes = getResolution(config.DYE_RESOLUTION);
  
      const texType = ext.halfFloatTexType;
      const rgba    = ext.formatRGBA;
      const rg      = ext.formatRG;
      const r       = ext.formatR;
      const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;
  
      if (dye == null)
          dye = createDoubleFBO(dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
      else
          dye = resizeDoubleFBO(dye, dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
  
      if (velocity == null)
          velocity = createDoubleFBO(simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
      else
          velocity = resizeDoubleFBO(velocity, simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
  
      divergence = createFBO      (simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
      curl       = createFBO      (simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
      pressure   = createDoubleFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
  
      initBloomFramebuffers();
      initSunraysFramebuffers();
  }
  
  function initBloomFramebuffers () {
      let res = getResolution(config.BLOOM_RESOLUTION);
  
      const texType = ext.halfFloatTexType;
      const rgba = ext.formatRGBA;
      const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;
  
      bloom = createFBO(res.width, res.height, rgba.internalFormat, rgba.format, texType, filtering);
  
      bloomFramebuffers.length = 0;
      for (let i = 0; i < config.BLOOM_ITERATIONS; i++)
      {
          let width = res.width >> (i + 1);
          let height = res.height >> (i + 1);
  
          if (width < 2 || height < 2) break;
  
          let fbo = createFBO(width, height, rgba.internalFormat, rgba.format, texType, filtering);
          bloomFramebuffers.push(fbo);
      }
  }
  
  function initSunraysFramebuffers () {
      let res = getResolution(config.SUNRAYS_RESOLUTION);
  
      const texType = ext.halfFloatTexType;
      const r = ext.formatR;
      const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;
  
      sunrays     = createFBO(res.width, res.height, r.internalFormat, r.format, texType, filtering);
      sunraysTemp = createFBO(res.width, res.height, r.internalFormat, r.format, texType, filtering);
  }
  
  function createFBO (w, h, internalFormat, format, type, param) {
      gl.activeTexture(gl.TEXTURE0);
      let texture = gl.createTexture();
      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
      gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, w, h, 0, format, type, null);
  
      let fbo = gl.createFramebuffer();
      gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
      gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
      gl.viewport(0, 0, w, h);
      gl.clear(gl.COLOR_BUFFER_BIT);
  
      let texelSizeX = 1.0 / w;
      let texelSizeY = 1.0 / h;
  
      return {
          texture,
          fbo,
          width: w,
          height: h,
          texelSizeX,
          texelSizeY,
          attach (id) {
              gl.activeTexture(gl.TEXTURE0 + id);
              gl.bindTexture(gl.TEXTURE_2D, texture);
              return id;
          }
      };
  }
  
  function createDoubleFBO (w, h, internalFormat, format, type, param) {
      let fbo1 = createFBO(w, h, internalFormat, format, type, param);
      let fbo2 = createFBO(w, h, internalFormat, format, type, param);
  
      return {
          width: w,
          height: h,
          texelSizeX: fbo1.texelSizeX,
          texelSizeY: fbo1.texelSizeY,
          get read () {
              return fbo1;
          },
          set read (value) {
              fbo1 = value;
          },
          get write () {
              return fbo2;
          },
          set write (value) {
              fbo2 = value;
          },
          swap () {
              let temp = fbo1;
              fbo1 = fbo2;
              fbo2 = temp;
          }
      }
  }
  
  function resizeFBO (target, w, h, internalFormat, format, type, param) {
      let newFBO = createFBO(w, h, internalFormat, format, type, param);
      copyProgram.bind();
      gl.uniform1i(copyProgram.uniforms.uTexture, target.attach(0));
      blit(newFBO.fbo);
      return newFBO;
  }
  
  function resizeDoubleFBO (target, w, h, internalFormat, format, type, param) {
      if (target.width == w && target.height == h)
          return target;
      target.read = resizeFBO(target.read, w, h, internalFormat, format, type, param);
      target.write = createFBO(w, h, internalFormat, format, type, param);
      target.width = w;
      target.height = h;
      target.texelSizeX = 1.0 / w;
      target.texelSizeY = 1.0 / h;
      return target;
  }
  
  function createTextureAsync (url) {
      let texture = gl.createTexture();
      gl.bindTexture(gl.TEXTURE_2D, texture);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
      gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
      gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, 1, 1, 0, gl.RGB, gl.UNSIGNED_BYTE, new Uint8Array([255, 255, 255]));
  
      let obj = {
          texture,
          width: 1,
          height: 1,
          attach (id) {
              gl.activeTexture(gl.TEXTURE0 + id);
              gl.bindTexture(gl.TEXTURE_2D, texture);
              return id;
          }
      };
  
      let image = new Image();
      image.onload = () => {
          obj.width = image.width;
          obj.height = image.height;
          gl.bindTexture(gl.TEXTURE_2D, texture);
          gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image);
      };
      image.src = url;
  
      return obj;
  }
  
  function updateKeywords () {
      let displayKeywords = [];
      if (config.SHADING) displayKeywords.push("SHADING");
      if (config.BLOOM) displayKeywords.push("BLOOM");
      if (config.SUNRAYS) displayKeywords.push("SUNRAYS");
      displayMaterial.setKeywords(displayKeywords);
  }
  
  updateKeywords();
  initFramebuffers();
  multipleSplats(parseInt(Math.random() * 20) + 5);
  
  let lastUpdateTime = Date.now();
  let colorUpdateTimer = 0.0;
  update();
  
  function update () {
      const dt = calcDeltaTime();
      if (resizeCanvas())
          initFramebuffers();
      updateColors(dt);
      applyInputs();
      if (!config.PAUSED)
          step(dt);
      render(null);
      requestAnimationFrame(update);
  }
  
  function calcDeltaTime () {
      let now = Date.now();
      let dt = (now - lastUpdateTime) / 1000;
      dt = Math.min(dt, 0.016666);
      lastUpdateTime = now;
      return dt;
  }
  
  function resizeCanvas () {
      let width = scaleByPixelRatio(canvas.clientWidth);
      let height = scaleByPixelRatio(canvas.clientHeight);
      if (canvas.width != width || canvas.height != height) {
          canvas.width = width;
          canvas.height = height;
          return true;
      }
      return false;
  }
  
  function updateColors (dt) {
      if (!config.COLORFUL) return;
  
      colorUpdateTimer += dt * config.COLOR_UPDATE_SPEED;
      if (colorUpdateTimer >= 1) {
          colorUpdateTimer = wrap(colorUpdateTimer, 0, 1);
          pointers.forEach(p => {
              p.color = generateColor();
          });
      }
  }
  
  function applyInputs () {
      if (splatStack.length > 0)
          multipleSplats(splatStack.pop());
  
      pointers.forEach(p => {
          if (p.moved) {
              p.moved = false;
              splatPointer(p);
          }
      });
  }
  
  function step (dt) {
      gl.disable(gl.BLEND);
      gl.viewport(0, 0, velocity.width, velocity.height);
  
      curlProgram.bind();
      gl.uniform2f(curlProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read.attach(0));
      blit(curl.fbo);
  
      vorticityProgram.bind();
      gl.uniform2f(vorticityProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read.attach(0));
      gl.uniform1i(vorticityProgram.uniforms.uCurl, curl.attach(1));
      gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
      gl.uniform1f(vorticityProgram.uniforms.dt, dt);
      blit(velocity.write.fbo);
      velocity.swap();
  
      divergenceProgram.bind();
      gl.uniform2f(divergenceProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read.attach(0));
      blit(divergence.fbo);
  
      clearProgram.bind();
      gl.uniform1i(clearProgram.uniforms.uTexture, pressure.read.attach(0));
      gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE);
      blit(pressure.write.fbo);
      pressure.swap();
  
      pressureProgram.bind();
      gl.uniform2f(pressureProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence.attach(0));
      for (let i = 0; i < config.PRESSURE_ITERATIONS; i++) {
          gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.read.attach(1));
          blit(pressure.write.fbo);
          pressure.swap();
      }
  
      gradienSubtractProgram.bind();
      gl.uniform2f(gradienSubtractProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      gl.uniform1i(gradienSubtractProgram.uniforms.uPressure, pressure.read.attach(0));
      gl.uniform1i(gradienSubtractProgram.uniforms.uVelocity, velocity.read.attach(1));
      blit(velocity.write.fbo);
      velocity.swap();
  
      advectionProgram.bind();
      gl.uniform2f(advectionProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
      if (!ext.supportLinearFiltering)
          gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, velocity.texelSizeX, velocity.texelSizeY);
      let velocityId = velocity.read.attach(0);
      gl.uniform1i(advectionProgram.uniforms.uVelocity, velocityId);
      gl.uniform1i(advectionProgram.uniforms.uSource, velocityId);
      gl.uniform1f(advectionProgram.uniforms.dt, dt);
      gl.uniform1f(advectionProgram.uniforms.dissipation, config.VELOCITY_DISSIPATION);
      blit(velocity.write.fbo);
      velocity.swap();
  
      gl.viewport(0, 0, dye.width, dye.height);
  
      if (!ext.supportLinearFiltering)
          gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, dye.texelSizeX, dye.texelSizeY);
      gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read.attach(0));
      gl.uniform1i(advectionProgram.uniforms.uSource, dye.read.attach(1));
      gl.uniform1f(advectionProgram.uniforms.dissipation, config.DENSITY_DISSIPATION);
      blit(dye.write.fbo);
      dye.swap();
  }
  
  function render (target) {
      if (config.BLOOM)
          applyBloom(dye.read, bloom);
      if (config.SUNRAYS) {
          applySunrays(dye.read, dye.write, sunrays);
          blur(sunrays, sunraysTemp, 1);
      }
  
      if (target == null || !config.TRANSPARENT) {
          gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
          gl.enable(gl.BLEND);
      }
      else {
          gl.disable(gl.BLEND);
      }
  
      let width = target == null ? gl.drawingBufferWidth : target.width;
      let height = target == null ? gl.drawingBufferHeight : target.height;
      gl.viewport(0, 0, width, height);
  
      let fbo = target == null ? null : target.fbo;
      if (!config.TRANSPARENT)
          drawColor(fbo, normalizeColor(config.BACK_COLOR));
      if (target == null && config.TRANSPARENT)
          drawCheckerboard(fbo);
      drawDisplay(fbo, width, height);
  }
  
  function drawColor (fbo, color) {
      colorProgram.bind();
      gl.uniform4f(colorProgram.uniforms.color, color.r, color.g, color.b, 1);
      blit(fbo);
  }
  
  function drawCheckerboard (fbo) {
      checkerboardProgram.bind();
      gl.uniform1f(checkerboardProgram.uniforms.aspectRatio, canvas.width / canvas.height);
      blit(fbo);
  }
  
  function drawDisplay (fbo, width, height) {
      displayMaterial.bind();
      if (config.SHADING)
          gl.uniform2f(displayMaterial.uniforms.texelSize, 1.0 / width, 1.0 / height);
      gl.uniform1i(displayMaterial.uniforms.uTexture, dye.read.attach(0));
      if (config.BLOOM) {
          gl.uniform1i(displayMaterial.uniforms.uBloom, bloom.attach(1));
          gl.uniform1i(displayMaterial.uniforms.uDithering, ditheringTexture.attach(2));
          let scale = getTextureScale(ditheringTexture, width, height);
          gl.uniform2f(displayMaterial.uniforms.ditherScale, scale.x, scale.y);
      }
      if (config.SUNRAYS)
          gl.uniform1i(displayMaterial.uniforms.uSunrays, sunrays.attach(3));
      blit(fbo);
  }
  
  function applyBloom (source, destination) {
      if (bloomFramebuffers.length < 2)
          return;
  
      let last = destination;
  
      gl.disable(gl.BLEND);
      bloomPrefilterProgram.bind();
      let knee = config.BLOOM_THRESHOLD * config.BLOOM_SOFT_KNEE + 0.0001;
      let curve0 = config.BLOOM_THRESHOLD - knee;
      let curve1 = knee * 2;
      let curve2 = 0.25 / knee;
      gl.uniform3f(bloomPrefilterProgram.uniforms.curve, curve0, curve1, curve2);
      gl.uniform1f(bloomPrefilterProgram.uniforms.threshold, config.BLOOM_THRESHOLD);
      gl.uniform1i(bloomPrefilterProgram.uniforms.uTexture, source.attach(0));
      gl.viewport(0, 0, last.width, last.height);
      blit(last.fbo);
  
      bloomBlurProgram.bind();
      for (let i = 0; i < bloomFramebuffers.length; i++) {
          let dest = bloomFramebuffers[i];
          gl.uniform2f(bloomBlurProgram.uniforms.texelSize, last.texelSizeX, last.texelSizeY);
          gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
          gl.viewport(0, 0, dest.width, dest.height);
          blit(dest.fbo);
          last = dest;
      }
  
      gl.blendFunc(gl.ONE, gl.ONE);
      gl.enable(gl.BLEND);
  
      for (let i = bloomFramebuffers.length - 2; i >= 0; i--) {
          let baseTex = bloomFramebuffers[i];
          gl.uniform2f(bloomBlurProgram.uniforms.texelSize, last.texelSizeX, last.texelSizeY);
          gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
          gl.viewport(0, 0, baseTex.width, baseTex.height);
          blit(baseTex.fbo);
          last = baseTex;
      }
  
      gl.disable(gl.BLEND);
      bloomFinalProgram.bind();
      gl.uniform2f(bloomFinalProgram.uniforms.texelSize, last.texelSizeX, last.texelSizeY);
      gl.uniform1i(bloomFinalProgram.uniforms.uTexture, last.attach(0));
      gl.uniform1f(bloomFinalProgram.uniforms.intensity, config.BLOOM_INTENSITY);
      gl.viewport(0, 0, destination.width, destination.height);
      blit(destination.fbo);
  }
  
  function applySunrays (source, mask, destination) {
      gl.disable(gl.BLEND);
      sunraysMaskProgram.bind();
      gl.uniform1i(sunraysMaskProgram.uniforms.uTexture, source.attach(0));
      gl.viewport(0, 0, mask.width, mask.height);
      blit(mask.fbo);
  
      sunraysProgram.bind();
      gl.uniform1f(sunraysProgram.uniforms.weight, config.SUNRAYS_WEIGHT);
      gl.uniform1i(sunraysProgram.uniforms.uTexture, mask.attach(0));
      gl.viewport(0, 0, destination.width, destination.height);
      blit(destination.fbo);
  }
  
  function blur (target, temp, iterations) {
      blurProgram.bind();
      for (let i = 0; i < iterations; i++) {
          gl.uniform2f(blurProgram.uniforms.texelSize, target.texelSizeX, 0.0);
          gl.uniform1i(blurProgram.uniforms.uTexture, target.attach(0));
          blit(temp.fbo);
  
          gl.uniform2f(blurProgram.uniforms.texelSize, 0.0, target.texelSizeY);
          gl.uniform1i(blurProgram.uniforms.uTexture, temp.attach(0));
          blit(target.fbo);
      }
  }
  
  function splatPointer (pointer) {
      let dx = pointer.deltaX * config.SPLAT_FORCE;
      let dy = pointer.deltaY * config.SPLAT_FORCE;
      splat(pointer.texcoordX, pointer.texcoordY, dx, dy, pointer.color);
  }
  
  function multipleSplats (amount) {
      for (let i = 0; i < amount; i++) {
          const color = generateColor();
          color.r *= 10.0;
          color.g *= 10.0;
          color.b *= 10.0;
          const x = Math.random();
          const y = Math.random();
          const dx = 1000 * (Math.random() - 0.5);
          const dy = 1000 * (Math.random() - 0.5);
          splat(x, y, dx, dy, color);
      }
  }
  
  function splat (x, y, dx, dy, color) {
      gl.viewport(0, 0, velocity.width, velocity.height);
      splatProgram.bind();
      gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read.attach(0));
      gl.uniform1f(splatProgram.uniforms.aspectRatio, canvas.width / canvas.height);
      gl.uniform2f(splatProgram.uniforms.point, x, y);
      gl.uniform3f(splatProgram.uniforms.color, dx, dy, 0.0);
      gl.uniform1f(splatProgram.uniforms.radius, correctRadius(config.SPLAT_RADIUS / 100.0));
      blit(velocity.write.fbo);
      velocity.swap();
  
      gl.viewport(0, 0, dye.width, dye.height);
      gl.uniform1i(splatProgram.uniforms.uTarget, dye.read.attach(0));
      gl.uniform3f(splatProgram.uniforms.color, color.r, color.g, color.b);
      blit(dye.write.fbo);
      dye.swap();
  }
  
  function correctRadius (radius) {
      let aspectRatio = canvas.width / canvas.height;
      if (aspectRatio > 1)
          radius *= aspectRatio;
      return radius;
  }
  
  canvas.addEventListener('mousedown', e => {
      let posX = scaleByPixelRatio(e.offsetX);
      let posY = scaleByPixelRatio(e.offsetY);
      let pointer = pointers.find(p => p.id == -1);
      if (pointer == null)
          pointer = new pointerPrototype();
      updatePointerDownData(pointer, -1, posX, posY);
  });
  
  canvas.addEventListener('mousemove', e => {
      let posX = scaleByPixelRatio(e.offsetX);
      let posY = scaleByPixelRatio(e.offsetY);
      updatePointerMoveData(pointers[0], posX, posY);
  });
  
  window.addEventListener('mouseup', () => {
      updatePointerUpData(pointers[0]);
  });
  
  canvas.addEventListener('touchstart', e => {
      e.preventDefault();
      const touches = e.targetTouches;
      while (touches.length >= pointers.length)
          pointers.push(new pointerPrototype());
      for (let i = 0; i < touches.length; i++) {
          let posX = scaleByPixelRatio(touches[i].pageX);
          let posY = scaleByPixelRatio(touches[i].pageY);
          updatePointerDownData(pointers[i + 1], touches[i].identifier, posX, posY);
      }
  });
  
  canvas.addEventListener('touchmove', e => {
      e.preventDefault();
      const touches = e.targetTouches;
      for (let i = 0; i < touches.length; i++) {
          let posX = scaleByPixelRatio(touches[i].pageX);
          let posY = scaleByPixelRatio(touches[i].pageY);
          updatePointerMoveData(pointers[i + 1], posX, posY);
      }
  }, false);
  
  window.addEventListener('touchend', e => {
      const touches = e.changedTouches;
      for (let i = 0; i < touches.length; i++)
      {
          let pointer = pointers.find(p => p.id == touches[i].identifier);
          updatePointerUpData(pointer);
      }
  });
  
  window.addEventListener('keydown', e => {
      if (e.code === 'KeyP')
          config.PAUSED = !config.PAUSED;
      if (e.key === ' ')
          splatStack.push(parseInt(Math.random() * 20) + 5);
  });
  
  function updatePointerDownData (pointer, id, posX, posY) {
      pointer.id = id;
      pointer.down = true;
      pointer.moved = false;
      pointer.texcoordX = posX / canvas.width;
      pointer.texcoordY = 1.0 - posY / canvas.height;
      pointer.prevTexcoordX = pointer.texcoordX;
      pointer.prevTexcoordY = pointer.texcoordY;
      pointer.deltaX = 0;
      pointer.deltaY = 0;
      pointer.color = generateColor();
  }
  
  function updatePointerMoveData (pointer, posX, posY) {
      pointer.moved = pointer.down;
      pointer.prevTexcoordX = pointer.texcoordX;
      pointer.prevTexcoordY = pointer.texcoordY;
      pointer.texcoordX = posX / canvas.width;
      pointer.texcoordY = 1.0 - posY / canvas.height;
      pointer.deltaX = correctDeltaX(pointer.texcoordX - pointer.prevTexcoordX);
      pointer.deltaY = correctDeltaY(pointer.texcoordY - pointer.prevTexcoordY);
  }
  
  function updatePointerUpData (pointer) {
      pointer.down = false;
  }
  
  function correctDeltaX (delta) {
      let aspectRatio = canvas.width / canvas.height;
      if (aspectRatio < 1) delta *= aspectRatio;
      return delta;
  }
  
  function correctDeltaY (delta) {
      let aspectRatio = canvas.width / canvas.height;
      if (aspectRatio > 1) delta /= aspectRatio;
      return delta;
  }
  
  function generateColor () {
      let c = HSVtoRGB(Math.random(), 1.0, 1.0);
      c.r *= 0.15;
      c.g *= 0.15;
      c.b *= 0.15;
      return c;
  }
  
  function HSVtoRGB (h, s, v) {
      let r, g, b, i, f, p, q, t;
      i = Math.floor(h * 6);
      f = h * 6 - i;
      p = v * (1 - s);
      q = v * (1 - f * s);
      t = v * (1 - (1 - f) * s);
  
      switch (i % 6) {
          case 0: r = v, g = t, b = p; break;
          case 1: r = q, g = v, b = p; break;
          case 2: r = p, g = v, b = t; break;
          case 3: r = p, g = q, b = v; break;
          case 4: r = t, g = p, b = v; break;
          case 5: r = v, g = p, b = q; break;
      }
  
      return {
          r,
          g,
          b
      };
  }
  
  function normalizeColor (input) {
      let output = {
          r: input.r / 255,
          g: input.g / 255,
          b: input.b / 255
      };
      return output;
  }
  
  function wrap (value, min, max) {
      let range = max - min;
      if (range == 0) return min;
      return (value - min) % range + min;
  }
  
  function getResolution (resolution) {
      let aspectRatio = gl.drawingBufferWidth / gl.drawingBufferHeight;
      if (aspectRatio < 1)
          aspectRatio = 1.0 / aspectRatio;
  
      let min = Math.round(resolution);
      let max = Math.round(resolution * aspectRatio);
  
      if (gl.drawingBufferWidth > gl.drawingBufferHeight)
          return { width: max, height: min };
      else
          return { width: min, height: max };
  }
  
  function getTextureScale (texture, width, height) {
      return {
          x: width / texture.width,
          y: height / texture.height
      };
  }
  
  function scaleByPixelRatio (input) {
      let pixelRatio = window.devicePixelRatio || 1;
      return Math.floor(input * pixelRatio);
  }
  
  function hashCode (s) {
      if (s.length == 0) return 0;
      let hash = 0;
      for (let i = 0; i < s.length; i++) {
          hash = (hash << 5) - hash + s.charCodeAt(i);
          hash |= 0; // Convert to 32bit integer
      }
      return hash;
  };