新增: 壁纸切换（主题/本地图片/Bing/纯色渐变）

web/themes/particles.html

@@ -0,0 +1,60 @@
+<canvas id="canvas" style="position:fixed;top:0;left:0;width:100%;height:100%;z-index:1;"></canvas>
+<script>
+var canvas = document.getElementById('canvas');
+var ctx = canvas.getContext('2d');
+
+function resizeCanvas() {
+  canvas.width = window.innerWidth;
+  canvas.height = window.innerHeight;
+}
+resizeCanvas();
+window.addEventListener('resize', resizeCanvas);
+
+var particles = [];
+for (var i = 0; i < 80; i++) {
+  particles.push({
+    x: Math.random() * canvas.width,
+    y: Math.random() * canvas.height,
+    r: Math.random() * 3 + 1,
+    vx: (Math.random() - 0.5) * 0.5,
+    vy: -(Math.random() * 0.8 + 0.2),
+    alpha: Math.random() * 0.5 + 0.2,
+    hue: Math.random() * 60 + 200
+  });
+}
+
+var FPS = 15, lastFrame = 0;
+
+function render(ts) {
+  requestAnimationFrame(render);
+  if (ts - lastFrame < 1000 / FPS) return;
+  lastFrame = ts;
+
+  var w = canvas.width, h = canvas.height;
+  ctx.fillStyle = 'rgba(5, 5, 15, 0.15)';
+  ctx.fillRect(0, 0, w, h);
+
+  for (var i = 0; i < particles.length; i++) {
+    var p = particles[i];
+    p.x += p.vx;
+    p.y += p.vy;
+    if (p.y < -20) { p.y = h + 20; p.x = Math.random() * w; }
+    if (p.x < -20) p.x = w + 20;
+    if (p.x > w + 20) p.x = -20;
+
+    var grad = ctx.createRadialGradient(p.x, p.y, 0, p.x, p.y, p.r * 4);
+    grad.addColorStop(0, 'hsla(' + p.hue + ', 70%, 70%, ' + p.alpha + ')');
+    grad.addColorStop(1, 'hsla(' + p.hue + ', 70%, 70%, 0)');
+    ctx.beginPath();
+    ctx.arc(p.x, p.y, p.r * 4, 0, Math.PI * 2);
+    ctx.fillStyle = grad;
+    ctx.fill();
+
+    ctx.beginPath();
+    ctx.arc(p.x, p.y, p.r, 0, Math.PI * 2);
+    ctx.fillStyle = 'hsla(' + p.hue + ', 80%, 80%, ' + (p.alpha + 0.3) + ')';
+    ctx.fill();
+  }
+}
+requestAnimationFrame(render);
+</script>