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