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index.html
149 lines (123 loc) · 2.95 KB
/
index.html
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<!DOCTYPE html>
<html>
<head>
<title>Snake</title>
<style>
html,
body {
height: 100%;
margin: 0;
}
body {
background: black;
display: flex;
align-items: center;
justify-content: center;
}
canvas {
border: 2px solid white;
}
</style>
</head>
<body>
<canvas width="400" height="400" id="game"></canvas>
<script>
var canvas = document.getElementById('game');
var context = canvas.getContext('2d');
var grid = 16;
var snake = {
x: 160,
y: 160,
dx: grid,
dy: 0,
cells: [],
maxCells: 4
};
var count = 0;
var apple = {
x: 320,
y: 320
};
function getRandomInt(min, max) {
return Math.floor(Math.random() * (max - min)) + min;
}
// game loop
function loop() {
requestAnimationFrame(loop);
// slow game loop to 15 fps instead of 60 - 60/15 = 4
if (++count < 4) {
return;
}
count = 0;
context.clearRect(0, 0, canvas.width, canvas.height);
snake.x += snake.dx;
snake.y += snake.dy;
// wrap snake position on edge of screen
if (snake.x < 0) {
snake.x = canvas.width - grid;
} else if (snake.x >= canvas.width) {
snake.x = 0;
}
if (snake.y < 0) {
snake.y = canvas.height - grid;
} else if (snake.y >= canvas.height) {
snake.y = 0;
}
// keep track of where snake has been. front of the array is always the head
snake.cells.unshift({
x: snake.x,
y: snake.y
});
// remove cells as we move away from them
if (snake.cells.length > snake.maxCells) {
snake.cells.pop();
}
// draw apple
context.fillStyle = 'red';
context.fillRect(apple.x, apple.y, grid - 1, grid - 1);
// draw snake
context.fillStyle = 'green';
snake.cells.forEach(function(cell, index) {
context.fillRect(cell.x, cell.y, grid - 1, grid - 1);
// snake ate apple
if (cell.x === apple.x && cell.y === apple.y) {
snake.maxCells++;
apple.x = getRandomInt(0, 25) * grid;
apple.y = getRandomInt(0, 25) * grid;
}
// check collision with all cells after this one (modified bubble sort)
for (var i = index + 1; i < snake.cells.length; i++) {
// collision. reset game
if (cell.x === snake.cells[i].x && cell.y === snake.cells[i].y) {
snake.x = 160;
snake.y = 160;
snake.cells = [];
snake.maxCells = 4;
snake.dx = grid;
snake.dy = 0;
apple.x = getRandomInt(0, 25) * grid;
apple.y = getRandomInt(0, 25) * grid;
}
}
});
}
document.addEventListener('keydown', function(e) {
// prevent snake from backtracking on itself
if (e.which === 37 && snake.dx === 0) {
snake.dx = -grid;
snake.dy = 0;
} else if (e.which === 38 && snake.dy === 0) {
snake.dy = -grid;
snake.dx = 0;
} else if (e.which === 39 && snake.dx === 0) {
snake.dx = grid;
snake.dy = 0;
} else if (e.which === 40 && snake.dy === 0) {
snake.dy = grid;
snake.dx = 0;
}
});
requestAnimationFrame(loop);
</script>
</body>
</html>