text: class Ground {
      constructor(game) {
          this.game = game
          this.grounds = []
          this.skipCount = 4
          this.init()
      }
  
      init() {
          for (let i = 0; i < 15; i++) {
              let g = new Img(this.game, 'ground')
              g.y = 370
              g.x = i * g.w
              this.grounds.push(g)
          }
      }
  
      draw() {
          for (let g of this.grounds) {
              g.draw()
          }
      }
  
      update() {
          // debug
  
          this.skipCount--
          let offset = -5
          if (this.skipCount == 0) {
              this.skipCount = 4
              offset = 15
          }
          for (let g of this.grounds) {
              g.x += offset
          }
      }
  }
  