Skip to content

Instantly share code, notes, and snippets.

@straker
Last active April 16, 2024 08:49
Show Gist options
  • Star 75 You must be signed in to star a gist
  • Fork 27 You must be signed in to fork a gist
  • Save straker/3c98304f8a6a9174efd8292800891ea1 to your computer and use it in GitHub Desktop.
Save straker/3c98304f8a6a9174efd8292800891ea1 to your computer and use it in GitHub Desktop.
Basic Tetris HTML and JavaScript Game

Basic Tetris HTML and JavaScript Game

This is a basic implementation of the game Tetris, but it's missing a few things intentionally and they're left as further exploration for the reader.

Further Exploration

Important note: I will answer questions about the code but will not add more features or answer questions about adding more features. This series is meant to give a basic outline of the game but nothing more.

License

(CC0 1.0 Universal) You're free to use this game and code in any project, personal or commercial. There's no need to ask permission before using these. Giving attribution is not required, but appreciated.

Other Basic Games

Support

Basic HTML Games are made possible by users like you. When you become a Patron, you get access to behind the scenes development logs, the ability to vote on which games I work on next, and early access to the next Basic HTML Game.

Top Patrons

  • Karar Al-Remahy
  • UnbrandedTech
  • Innkeeper Games
  • Nezteb
<!DOCTYPE html>
<html>
<head>
<title>Basic Tetris HTML Game</title>
<meta charset="UTF-8">
<style>
html, body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
canvas {
border: 1px solid white;
}
</style>
</head>
<body>
<canvas width="320" height="640" id="game"></canvas>
<script>
// https://tetris.fandom.com/wiki/Tetris_Guideline
// get a random integer between the range of [min,max]
// @see https://stackoverflow.com/a/1527820/2124254
function getRandomInt(min, max) {
min = Math.ceil(min);
max = Math.floor(max);
return Math.floor(Math.random() * (max - min + 1)) + min;
}
// generate a new tetromino sequence
// @see https://tetris.fandom.com/wiki/Random_Generator
function generateSequence() {
const sequence = ['I', 'J', 'L', 'O', 'S', 'T', 'Z'];
while (sequence.length) {
const rand = getRandomInt(0, sequence.length - 1);
const name = sequence.splice(rand, 1)[0];
tetrominoSequence.push(name);
}
}
// get the next tetromino in the sequence
function getNextTetromino() {
if (tetrominoSequence.length === 0) {
generateSequence();
}
const name = tetrominoSequence.pop();
const matrix = tetrominos[name];
// I and O start centered, all others start in left-middle
const col = playfield[0].length / 2 - Math.ceil(matrix[0].length / 2);
// I starts on row 21 (-1), all others start on row 22 (-2)
const row = name === 'I' ? -1 : -2;
return {
name: name, // name of the piece (L, O, etc.)
matrix: matrix, // the current rotation matrix
row: row, // current row (starts offscreen)
col: col // current col
};
}
// rotate an NxN matrix 90deg
// @see https://codereview.stackexchange.com/a/186834
function rotate(matrix) {
const N = matrix.length - 1;
const result = matrix.map((row, i) =>
row.map((val, j) => matrix[N - j][i])
);
return result;
}
// check to see if the new matrix/row/col is valid
function isValidMove(matrix, cellRow, cellCol) {
for (let row = 0; row < matrix.length; row++) {
for (let col = 0; col < matrix[row].length; col++) {
if (matrix[row][col] && (
// outside the game bounds
cellCol + col < 0 ||
cellCol + col >= playfield[0].length ||
cellRow + row >= playfield.length ||
// collides with another piece
playfield[cellRow + row][cellCol + col])
) {
return false;
}
}
}
return true;
}
// place the tetromino on the playfield
function placeTetromino() {
for (let row = 0; row < tetromino.matrix.length; row++) {
for (let col = 0; col < tetromino.matrix[row].length; col++) {
if (tetromino.matrix[row][col]) {
// game over if piece has any part offscreen
if (tetromino.row + row < 0) {
return showGameOver();
}
playfield[tetromino.row + row][tetromino.col + col] = tetromino.name;
}
}
}
// check for line clears starting from the bottom and working our way up
for (let row = playfield.length - 1; row >= 0; ) {
if (playfield[row].every(cell => !!cell)) {
// drop every row above this one
for (let r = row; r >= 0; r--) {
for (let c = 0; c < playfield[r].length; c++) {
playfield[r][c] = playfield[r-1][c];
}
}
}
else {
row--;
}
}
tetromino = getNextTetromino();
}
// show the game over screen
function showGameOver() {
cancelAnimationFrame(rAF);
gameOver = true;
context.fillStyle = 'black';
context.globalAlpha = 0.75;
context.fillRect(0, canvas.height / 2 - 30, canvas.width, 60);
context.globalAlpha = 1;
context.fillStyle = 'white';
context.font = '36px monospace';
context.textAlign = 'center';
context.textBaseline = 'middle';
context.fillText('GAME OVER!', canvas.width / 2, canvas.height / 2);
}
const canvas = document.getElementById('game');
const context = canvas.getContext('2d');
const grid = 32;
const tetrominoSequence = [];
// keep track of what is in every cell of the game using a 2d array
// tetris playfield is 10x20, with a few rows offscreen
const playfield = [];
// populate the empty state
for (let row = -2; row < 20; row++) {
playfield[row] = [];
for (let col = 0; col < 10; col++) {
playfield[row][col] = 0;
}
}
// how to draw each tetromino
// @see https://tetris.fandom.com/wiki/SRS
const tetrominos = {
'I': [
[0,0,0,0],
[1,1,1,1],
[0,0,0,0],
[0,0,0,0]
],
'J': [
[1,0,0],
[1,1,1],
[0,0,0],
],
'L': [
[0,0,1],
[1,1,1],
[0,0,0],
],
'O': [
[1,1],
[1,1],
],
'S': [
[0,1,1],
[1,1,0],
[0,0,0],
],
'Z': [
[1,1,0],
[0,1,1],
[0,0,0],
],
'T': [
[0,1,0],
[1,1,1],
[0,0,0],
]
};
// color of each tetromino
const colors = {
'I': 'cyan',
'O': 'yellow',
'T': 'purple',
'S': 'green',
'Z': 'red',
'J': 'blue',
'L': 'orange'
};
let count = 0;
let tetromino = getNextTetromino();
let rAF = null; // keep track of the animation frame so we can cancel it
let gameOver = false;
// game loop
function loop() {
rAF = requestAnimationFrame(loop);
context.clearRect(0,0,canvas.width,canvas.height);
// draw the playfield
for (let row = 0; row < 20; row++) {
for (let col = 0; col < 10; col++) {
if (playfield[row][col]) {
const name = playfield[row][col];
context.fillStyle = colors[name];
// drawing 1 px smaller than the grid creates a grid effect
context.fillRect(col * grid, row * grid, grid-1, grid-1);
}
}
}
// draw the active tetromino
if (tetromino) {
// tetromino falls every 35 frames
if (++count > 35) {
tetromino.row++;
count = 0;
// place piece if it runs into anything
if (!isValidMove(tetromino.matrix, tetromino.row, tetromino.col)) {
tetromino.row--;
placeTetromino();
}
}
context.fillStyle = colors[tetromino.name];
for (let row = 0; row < tetromino.matrix.length; row++) {
for (let col = 0; col < tetromino.matrix[row].length; col++) {
if (tetromino.matrix[row][col]) {
// drawing 1 px smaller than the grid creates a grid effect
context.fillRect((tetromino.col + col) * grid, (tetromino.row + row) * grid, grid-1, grid-1);
}
}
}
}
}
// listen to keyboard events to move the active tetromino
document.addEventListener('keydown', function(e) {
if (gameOver) return;
// left and right arrow keys (move)
if (e.which === 37 || e.which === 39) {
const col = e.which === 37
? tetromino.col - 1
: tetromino.col + 1;
if (isValidMove(tetromino.matrix, tetromino.row, col)) {
tetromino.col = col;
}
}
// up arrow key (rotate)
if (e.which === 38) {
const matrix = rotate(tetromino.matrix);
if (isValidMove(matrix, tetromino.row, tetromino.col)) {
tetromino.matrix = matrix;
}
}
// down arrow key (drop)
if(e.which === 40) {
const row = tetromino.row + 1;
if (!isValidMove(tetromino.matrix, row, tetromino.col)) {
tetromino.row = row - 1;
placeTetromino();
return;
}
tetromino.row = row;
}
});
// start the game
rAF = requestAnimationFrame(loop);
</script>
</body>
</html>
@kampiler
Copy link

kampiler commented Nov 13, 2023

я быстрый сброс фигуры реализовал так:

  // space key (fast drop)
  if(e.which === 32) {
     while(!downOne()){
     }
  }
  // down arrow key (drop)
  if(e.which === 40) {
     downOne();
  }

function downOne()
  {
   const row = tetromino.row + 1;
   if (!isValidMove(tetromino.matrix, row, tetromino.col))
     {
      tetromino.row = row - 1;

      placeTetromino();
      return true;
     }
   tetromino.row = row;
   return false;
  }

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment