void walk() {

		// try until you find an available move
		while (true) {
			float r = p5.random(1);
			if (r < 0.25f && !p5.visited[x-step][y]) {
				x -= step; 
				break;
			}

			else if (r < 0.50f && !p5.visited[x+step][y]) {
				x += step; 

				break;
			}
			else if (r < 0.75f && !p5.visited[x][y-step]) { 
				y -= step; 
				break;
			}

			else if (r < 1.00f && !p5.visited[x][y+step]) { 
				y += step; 
				break;
			}
		}
		p5.visited[x][y] = true;

		//if can't find a position die
	}