function checkRotation(piece, x, y) {
    let newPiece;
    for (let i = 0; i < tetrominoes.length; i++) {
      if (arraysEqual(tetrominoes[i], piece)) {
        let newRotate = rotateClockwise(tetrominoes[i]);
        if (!checkCollision(newRotate, x, y)) {
          newPiece = newRotate;
          break;
        } else {
          let newRotate2 = rotateClockwise(newRotate);
          if (!checkCollision(newRotate2, x, y)) newPiece = newRotate2;
        }
      }
    }
    return newPiece;
  }

  function rotateClockwise(piece) {
    let rotateRow = piece[0][1] + piece.slice(0, piece.length - 1).reduce((a, b) => a + b, 0);
    let rotateCol = piece[0][0] - piece.slice(1).reduce((a, b) => a + b, 0);
    return piece.slice(1).map((a) => [rotateCol, -a[0] + rotateRow])
  }

  function arraysEqual(a, b) {
    return a.length === b.length && a.every(function (element, index) {
      return element === b[index]
    })
  }

  document.addEventListener("keydown", function (event) {
    key = event.key;
    if (event.key === "ArrowLeft" || event.key === 37) key = 37;
    if (event.key === "ArrowRight" || event.key === 39) key = 39;
    if (event.key === "ArrowUp" || event.key === 38) key = 38;
    if (event.key === "ArrowDown" || event.key === 40) key = 40;
    if (event.key === "space" || event.key === 32) key = 32;

    if (event.key !== 39 && event.key !== 37) update();
  });

  let paused = false;
  let key;
  function pause() {
    paused = !paused;
  }

  function restart() {
    score = 0;
    level = 1;
    clearedLines = 0;
    currentPiece = null;
    currentX = Math.floor(canvas.width / 2) + 2;
    currentY = 0;
    grid = Array(20).fill(0).map(() => Array(10).fill(0));
    nextPiece = Math.floor(Math.random() * tetrominoes.length);
  }

  function randomSeed() {
    return Math.floor(Math.random() * tetrominoes.length);
  }

  currentPiece = nextPiece;
  update();