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arctic_circle.html
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arctic_circle.html
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<!DOCTYPE html>
<html>
<head>
<title>Arctic Circle</title>
<link rel="icon" href="res/favicon.ico">
<script type="text/javascript">
// [1] ^ (2)
// (8) [3]
// < >
// [7] (4)
// (6) v [5]
// 0: 65 1: 12
// 12 65
// 0: 38 1: 83
// 47 74
function pretty(a) {
var s = "";
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < (a.length - a[i].length) / 2; ++j) s += " ";
s += a[i].join("");
s += "\n";
}
console.log(s);
}
function make(size) {
var a = Array(2 * size);
for (var i = 0; i < size; ++i) {
a[i] = Array(2 * i + 2).fill(0);
a[2 * size - 1 - i] = Array(2 * i + 2).fill(0);
}
return a;
}
function parity(a, i, j) {
if (i < a.length / 2) {
return j % 2;
} else {
return (j + 1) % 2;
}
}
function dj(a, i, j, di) {
if (di == 1) {
var tj = j;
if (i < a.length / 2 - 1) {
tj += 1;
} else if (i >= a.length / 2) {
tj -= 1;
}
if (tj >= 0 && i + 1 < a.length && tj < a[i + 1].length) {
return tj;
}
} else if (di == -1) {
var tj = j;
if (i < a.length / 2) {
tj -= 1;
} else if (i > a.length / 2) {
tj += 1;
}
if (tj >= 0 && i - 1 >= 0 && tj < a[i - 1].length) {
return tj;
}
}
return null;
}
function fill(a) {
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < a[i].length; ++j) {
if (a[i][j] == 0) {
var tj0 = dj(a, i, j, 1);
var tj1 = dj(a, i, j + 1, 1);
console.assert(tj0 !== null);
console.assert(tj1 !== null);
console.assert(a[i + 1][tj0] == 0);
console.assert(a[i][j + 1] == 0);
console.assert(a[i + 1][tj1] == 0);
if (Math.random() < 0.5) {
if (parity(a, i, j)) {
a[i][j] = 6;
a[i + 1][tj0] = 5;
a[i][j + 1] = 1;
a[i + 1][tj1] = 2;
} else {
a[i][j] = 1;
a[i + 1][tj0] = 2;
a[i][j + 1] = 6;
a[i + 1][tj1] = 5;
}
} else {
if (parity(a, i, j)) {
a[i][j] = 3;
a[i + 1][tj0] = 8;
a[i][j + 1] = 4;
a[i + 1][tj1] = 7;
} else {
a[i][j] = 8;
a[i + 1][tj0] = 3;
a[i][j + 1] = 7;
a[i + 1][tj1] = 4;
}
}
}
}
}
}
function grow(a) {
var b = make(1 + a.length / 2);
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < a[i].length; ++j) {
b[i + 1][j + 1] = a[i][j];
}
}
return b;
}
function cull(a) {
// 65 38
// 12 47
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < a[i].length; ++j) {
var tj0 = dj(a, i, j, 1);
var tj1 = dj(a, i, j + 1, 1);
if (tj0 === null || tj1 === null) continue;
if ((a[i][j] == 6 && a[i + 1][tj0] == 5 && a[i][j + 1] == 1 &&
a[i + 1][tj1] == 2) ||
(a[i][j] == 3 && a[i + 1][tj0] == 8 && a[i][j + 1] == 4 &&
a[i + 1][tj1] == 7)) {
a[i][j] = 0;
a[i + 1][tj0] = 0;
a[i][j + 1] = 0;
a[i + 1][tj1] = 0;
}
}
}
}
function shift(a) {
var b = make(a.length / 2);
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < a[i].length; ++j) {
if ((a[i][j] == 1 || a[i][j] == 2) && j > 0) {
console.assert(b[i][j - 1] == 0);
b[i][j - 1] = a[i][j];
} else if ((a[i][j] == 3 || a[i][j] == 4) && i < a.length - 1) {
var tj = dj(a, i, j, 1);
if (tj !== null) {
console.assert(b[i + 1][tj] == 0);
b[i + 1][tj] = a[i][j];
}
} else if ((a[i][j] == 5 || a[i][j] == 6) && j < a[i].length - 1) {
console.assert(b[i][j + 1] == 0);
b[i][j + 1] = a[i][j];
} else if ((a[i][j] == 7 || a[i][j] == 8) && j > 0) {
var tj = dj(a, i, j, -1);
if (tj !== null) {
console.assert(b[i - 1][tj] == 0);
b[i - 1][tj] = a[i][j];
}
}
}
}
return b;
}
// [1] ^ (2)
// (8) [3]
// < >
// [7] (4)
// (6) v [5]
var canvas = null;
var ctx = null;
function draw(a) {
if (canvas.clientWidth != canvas.width) canvas.width = canvas.clientWidth;
if (canvas.clientHeight != canvas.height) canvas.height = canvas.clientHeight;
var scale = Math.min(canvas.width, canvas.height) / a.length;
ctx.save();
ctx.fillStyle = 'black';
ctx.fillRect(0, 0, canvas.width, canvas.height);
ctx.scale(scale, scale);
for (var i = 0; i < a.length; ++i) {
for (var j = 0; j < a[i].length; ++j) {
if (a[i][j] % 2 == 0) continue;
var k = Math.floor(a[i][j] / 2);
var x = j + (a.length - a[i].length) / 2 + [0.05, 0.05, 0.05, -0.95][k];
var y = i + [0.05, 0.05, -0.95, 0.05][k];
var w = [0.9, 1.9, 0.9, 1.9][k];
var h = [1.9, 0.9, 1.9, 0.9][k];
ctx.fillStyle = ['red', 'green', 'blue', 'yellow'][k];
ctx.fillRect(x, y, w, h);
}
}
ctx.restore();
}
var run = false;
var a = make(1);
fill(a);
function canvasClick(cc) {
canvas = cc;
ctx = canvas.getContext('2d');
run = !run;
}
function loop() {
if (canvas) {
}
if (run) {
var b = grow(a);
cull(b);
a = shift(b);
fill(a);
draw(a);
}
window.setTimeout(loop, 100);
}
loop();
</script>
</head>
<body style="margin:0;">
<canvas style="width:100%;height:100%;" onclick="canvasClick(this)"></canvas>
<div style="width:100%;height:100%;position:absolute;left:0;top:0;z-index:-1;background-color:#000;color:#FFF;font-size:32px;text-align:center">Click me</div>
</body>
</html>