body {
display: flex;
justify-content: center;
align-items: center;
height: 100vh;
margin: 0;
background-color: #222;
}
canvas {
border: 1px solid #fff;
}
const canvas = document.getElementById(‘tetris’);
const ctx = canvas.getContext(‘2d’);
ctx.scale(20, 20);
function arenaSweep() {
outer: for (let y = arena.length – 1; y > 0; –y) {
for (let x = 0; x < arena[y].length; ++x) {
if (!arena[y][x]) {
continue outer;
}
}
const row = arena.splice(y, 1)[0].fill(0);
arena.unshift(row);
++y;
}
}
function collide(arena, player) {
const [m, o] = [player.matrix, player.pos];
for (let y = 0; y < m.length; ++y) {
for (let x = 0; x < m[y].length; ++x) {
if (m[y][x] && (arena[y + o.y] && arena[y + o.y][x + o.x]) !== 0) {
return true;
}
}
}
return false;
}
function createMatrix(w, h) {
const matrix = [];
while (h--) {
matrix.push(new Array(w).fill(0));
}
return matrix;
}
function createPiece(type) {
if (type === 'T') {
return [
[1, 1, 1],
[0, 1, 0],
[0, 0, 0],
];
} else if (type === 'O') {
return [
[2, 2],
[2, 2],
];
} else if (type === 'L') {
return [
[0, 3, 0],
[0, 3, 0],
[0, 3, 3],
];
} else if (type === 'J') {
return [
[0, 4, 0],
[0, 4, 0],
[4, 4, 0],
];
} else if (type === 'I') {
return [
[0, 5, 0, 0],
[0, 5, 0, 0],
[0, 5, 0, 0],
[0, 5, 0, 0],
];
} else if (type === 'S') {
return [
[0, 6, 6],
[6, 6, 0],
[0, 0, 0],
];
} else if (type === 'Z') {
return [
[7, 7, 0],
[0, 7, 7],
[0, 0, 0],
];
}
}
function draw() {
ctx.fillStyle = '#000';
ctx.fillRect(0, 0, canvas.width, canvas.height);
drawMatrix(arena, { x: 0, y: 0 });
drawMatrix(player.matrix, player.pos);
}
function drawMatrix(matrix, offset) {
matrix.forEach((row, y) => {
row.forEach((value, x) => {
if (value !== 0) {
ctx.fillStyle = ‘red’;
ctx.fillRect(x + offset.x, y + offset.y, 1, 1);
}
});
});
}
function merge(arena, player) {
player.matrix.forEach((row, y) => {
row.forEach((value, x) => {
if (value !== 0) {
arena[y + player.pos.y][x + player.pos.x] = value;
}
});
});
}
function playerDrop() {
player.pos.y++;
if (collide(arena, player)) {
player.pos.y–;
merge(arena, player);
playerReset();
arenaSweep();
}
dropCounter = 0;
}
function playerMove(offset) {
player.pos.x += offset;
if (collide(arena, player)) {
player.pos.x -= offset;
}
}
function playerReset() {
const pieces = ‘TOLJSIZ’;
player.matrix = createPiece(pieces[pieces.length * Math.random() | 0]);
player.pos.y = 0;
player.pos.x = (arena[0].length / 2 | 0) – (player.matrix[0].length / 2 | 0);
if (collide(arena, player)) {
arena.forEach(row => row.fill(0));
}
}
function playerRotate(dir) {
const pos = player.pos.x;
let offset = 1;
rotate(player.matrix, dir);
while (collide(arena, player)) {
player.pos.x += offset;
offset = -(offset + (offset > 0 ? 1 : -1));
if (offset > player.matrix[0].length) {
rotate(player.matrix, -dir);
player.pos.x = pos;
return;
}
}
}
function rotate(matrix, dir) {
for (let y = 0; y < matrix.length; ++y) {
for (let x = 0; x < y; ++x) {
[matrix[x][y], matrix[y][x]] = [matrix[y][x], matrix[x][y]];
}
}
if (dir > 0) {
matrix.forEach(row => row.reverse());
} else {
matrix.reverse();
}
}
let dropCounter = 0;
let dropInterval = 1000;
let lastTime = 0;
function update(time = 0) {
const deltaTime = time – lastTime;
lastTime = time;
dropCounter += deltaTime;
if (dropCounter > dropInterval) {
playerDrop();
}
draw();
requestAnimationFrame(update);
}
const arena = createMatrix(10, 20);
const player = {
pos: {x: 0, y: 0 },
matrix: null,
};
document.addEventListener(‘keydown’, (event) => {
if (event.key === ‘ArrowLeft’) {
playerMove(-1);
} else if (event.key === ‘ArrowRight’) {
playerMove(1);
} else if (event.key === ‘ArrowDown’) {
playerDrop();
} else if (event.key === ‘ArrowUp’) {
playerRotate(1);
}
});
playerReset();
update();
