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index.html
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<!DOCTYPE html>
<html>
<head>
<title>Terramino</title>
<style>
html,
body {
height: 100%;
margin: 0;
}
body {
/* background-image: url("https://raw.githubusercontent.com/hashicorp/learn-terramino/main/assets/background.png"); */
background-image: url("https://github.com/hashicorp/learn-terramino/raw/master/background.png");
display: flex;
align-items: center;
justify-content: center;
color: white;
font-family: Arial, Helvetica, sans-serif
}
h1 {
font-family: Impact, Charcoal, sans-serif
}
canvas {
border: 1px solid white;
}
.container {
position: relative;
margin: 0 auto;
}
.content {
position: relative;
left: 0;
top: 0;
}
</style>
</head>
<body>
<div class="container">
<div class="content">
<h1>Terramino</h1>
<p>Use left and right arrow keys to move blocks.<br />Use up arrow key to flip block.</p>
</div>
<div class="content">
<canvas width="320" height="640" id="game"></canvas>
</div>
</div>
<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--) {
playfield[r] = playfield[r - 1];
}
} 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: "#623CE4",
O: "#7C8797",
T: "#00BC7F",
S: "#CA2171",
Z: "#1563ff",
J: "#00ACFF",
L: "white"
};
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>