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HTML

              
                <canvas id="background"></canvas>
    <canvas id="players"></canvas>
              
            
!

CSS

              
                
body {
  background-color: black;
}
canvas {
  border: 15px gray groove;
  padding: 5px;
  position: absolute;
}

#background {
  z-index: 0;
}

#players {
  z-index: 1;
}
              
            
!

JS

              
                
const CANVAS_HEIGHT = 600;
const CANVAS_WIDTH = 600;
const WHITE_LEVEL = 0.48;
const BLACK = 0;
const WHITE = 1;
const COLORS = {
  [BLACK]: "black",
  [WHITE]: "white",
};
const PIXEL_RATIO = 5;
const MATRIX_DIMENSIONS = {
  height: CANVAS_HEIGHT / PIXEL_RATIO,
  width: CANVAS_WIDTH / PIXEL_RATIO,
};
const canvas = document.querySelector("#background");
const playersCanvas = document.querySelector("#players");
canvas.height = playersCanvas.height = CANVAS_HEIGHT;
canvas.width = playersCanvas.width = CANVAS_WIDTH;

function generateWhiteNoise(size, whiteLevel = 0.6) {
  return new Array(size)
    .fill(0)
    .map(() => (Math.random() >= whiteLevel ? BLACK : WHITE));
}

function calculatePixelValueByNeighbors(rowIndex, pixelIndex, matrix) {
  let sum = 0;
  for (let y = -1; y < 2; y++) {
    for (let x = -1; x < 2; x++) {
      if (
        !matrix[rowIndex + y] ||
        !matrix[rowIndex + y][pixelIndex + x]
      ) {
        sum -= 1;
      } else {
        sum += 1;
      }
    }
  }
  return sum > 0 ? WHITE : BLACK;
}

function copyMatrix(matrix) {
  return JSON.parse(JSON.stringify(matrix));
}

function cellularAutomaton(matrix) {
  const tmpMatrix = copyMatrix(matrix);
  tmpMatrix.forEach((row, rowIndex) => {
    row.forEach((pixel, pixelIndex) => {
      tmpMatrix[rowIndex][pixelIndex] = calculatePixelValueByNeighbors(
        rowIndex,
        pixelIndex,
        matrix
      );
    });
  });
  return tmpMatrix;
}

function areMatricesDifferent(matrixA, matrixB) {
  return JSON.stringify(matrixA) != JSON.stringify(matrixB);
}

function generateBackgroundPaths(matrix) {
  const wallsPath = new Path2D();
  const roadsPath = new Path2D();
  const mazePaths = {
    wallsPath,
    roadsPath,
  };

  matrix.forEach((pixelsRow, rowIndex) => {
    const y = rowIndex * PIXEL_RATIO;
    pixelsRow.forEach((pixel, pixelIndex) => {
      const x = pixelIndex * PIXEL_RATIO;
      const currPath = pixel === BLACK ? roadsPath : wallsPath;
      currPath.rect(x, y, PIXEL_RATIO, PIXEL_RATIO);
    });
  });

  return mazePaths;
}

function drawBackground(mazePaths) {
  const ctx = canvas.getContext("2d");
  ctx.clearRect(0, 0, CANVAS_HEIGHT, CANVAS_WIDTH);
  ctx.fillStyle = COLORS[BLACK];
  ctx.fill(mazePaths.roadsPath);

  ctx.fillStyle = COLORS[WHITE];
  ctx.fill(mazePaths.wallsPath);

  return mazePaths;
}

function generateBackground() {
  const matrices = {
    last: null,
    current: null,
  };

  matrices.current = new Array(MATRIX_DIMENSIONS.height)
    .fill(0)
    .map(() => {
    return generateWhiteNoise(MATRIX_DIMENSIONS.width, WHITE_LEVEL);
  });

  let count = 0;
  const ITERATIONS_LIMIT = 100;
  while (
    areMatricesDifferent(matrices.current, matrices.last) ||
    count > ITERATIONS_LIMIT
  ) {
    matrices.last = matrices.current;
    matrices.current = cellularAutomaton(matrices.last);
  }

  const backgroundPaths = generateBackgroundPaths(matrices.current);
  return drawBackground(backgroundPaths);
}

function isCircleInPath(circleData = { radius: 5, x: 5, y: 5 }, path) {
  const ctx = document.createElement("canvas").getContext("2d");
  const radius = circleData.radius;
  for (
    let x = circleData.x - radius;
    x <= circleData.x + 2 * radius;
    x += radius
  ) {
    for (
      let y = circleData.y - radius;
      y <= circleData.y + 2 * radius;
      y += radius
    ) {
      if (ctx.isPointInPath(path, x, y)) return true;
    }
  }
  return false;
}

function findAStartingPoint(wallsPaths, radius) {
  let x, y;
  let count = 0;
  do {
    count++;
    x = Math.floor(Math.random() * CANVAS_WIDTH);
    y = Math.floor(Math.random() * CANVAS_HEIGHT);
  } while (isCircleInPath({ radius, x, y }, wallsPaths) && count < 100);

  return { x, y };
}

function start(canvas, radius = 10) {
  const mazesPaths = generateBackground();
  const { x, y } = findAStartingPoint(mazesPaths.wallsPath, radius);
  renderPlayer(canvas, {currX: x, currY: y, playerRadius: radius}, mazesPaths.wallsPath);
}

function renderPlayer(canvas, {currX, currY, playerRadius}, wallsPath) {
  let radius = playerRadius, x = currX, y = currY;
  if (spaceClicked) {
    radius = 2;
  }
  const ctx = canvas.getContext("2d");
  if (clickedKey) {
    if (clickedKey.includes('Down') || clickedKey.includes('Up')) {
      y = currY + KEYBOARD_KEYS[clickedKey] * PIXEL_RATIO / 2;
    } else {
      x = currX + KEYBOARD_KEYS[clickedKey] * PIXEL_RATIO / 2;
    }
  }

  if (y - radius < 0 || y + radius >= CANVAS_HEIGHT || x - radius < 0 || x + radius >= CANVAS_WIDTH || isCircleInPath({radius, x, y}, wallsPath)) {
    x = currX;
    y = currY;
  } else {
    const playerPath = new Path2D();
    playerPath.arc(x, y, radius, 0, 2 * Math.PI);
    ctx.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);
    ctx.fillStyle = "blue";
    ctx.fill(playerPath);
  }

  requestAnimationFrame(() => renderPlayer(canvas, {currX: x, currY: y, playerRadius}, wallsPath));
}

const KEYBOARD_KEYS = {
  'ArrowUp': -1,
  'ArrowDown': 1,
  'ArrowLeft': -1,
  'ArrowRight': 1
};

let clickedKey;
let spaceClicked = false;

start(playersCanvas, 10);

document.addEventListener('keydown', (event) => {
  if (event.key === ' ') return spaceClicked = true;

  if (Object.keys(KEYBOARD_KEYS).includes(event.key)) {
    clickedKey = event.key;
  }
});

document.addEventListener('keyup', (event) => {
  if (event.key === ' ') return spaceClicked = false;

  if (clickedKey === event.key) {
    clickedKey = null;
  }
});
              
            
!
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