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Balls.
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<!DOCTYPE html> | |
<html> | |
<head> | |
<meta charset="utf-8" /> | |
<title>Balls.</title> | |
<style> | |
canvas { background-color: black; } | |
</style> | |
</head> | |
<body> | |
<canvas width="600" height="600" id="stage"></canvas> | |
<script> | |
var stage = document.getElementById("stage"); | |
var stageW = stage.width, | |
stageH = stage.height; | |
var ctx = stage.getContext("2d"); | |
function drawBall(ball) { | |
ctx.fillStyle = "#0080ff"; | |
ctx.beginPath(); | |
ctx.arc(ball.x, ball.y, ball.r, 0, Math.PI * 2); | |
ctx.closePath(); | |
ctx.fill(); | |
} | |
var balls = []; | |
var ballRadius = 20; | |
for (var i = 0; i < 10; i++) { | |
balls.push({ | |
x: Math.random() * (stageW - ballRadius * 2) + ballRadius, | |
y: Math.random() * (stageH - ballRadius * 2) + ballRadius, | |
r: ballRadius, | |
vx: (Math.random() - 0.5) * 10, | |
vy: (Math.random() - 0.5) * 10 | |
}); | |
} | |
function draw() { | |
ctx.globalAlpha = 0.2; | |
ctx.drawImage( | |
ctx.canvas, | |
5, | |
5, | |
ctx.canvas.width - 10, | |
ctx.canvas.height - 10, | |
0, 0, ctx.canvas.width, ctx.canvas.height); | |
ctx.globalAlpha = 0.02; | |
ctx.fillStyle = "#401000"; | |
ctx.fillRect(0, 0, stageW, stageH); | |
ctx.globalAlpha = 1; | |
balls.forEach(drawBall); | |
} | |
var accX = 0; | |
accY = 0.5; | |
function process() { | |
balls.forEach(function (ball) { | |
ball.x += ball.vx; | |
ball.y += ball.vy; | |
if (ball.x < ballRadius) { | |
ball.x = ballRadius; | |
ball.vx = -ball.vx; | |
} else if (ball.x > stageW - ballRadius) { | |
ball.x = stageW - ballRadius; | |
ball.vx = -ball.vx; | |
} | |
if (ball.y < ballRadius) { | |
ball.y = ballRadius; | |
ball.vy = -ball.vy; | |
} else if (ball.y > stageH - ballRadius) { | |
ball.y = stageH - ballRadius; | |
ball.vy = -ball.vy; | |
} | |
ball.vy += accY; | |
ball.vx += accX; | |
}); | |
} | |
function tick() { | |
draw(); | |
process(); | |
window.setTimeout(tick, 1000 / 25); | |
} | |
tick(); | |
</script> | |
</body> | |
</html> |
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