function initParticles() { var n = Math.min(C.maxCount, Math.round(W * H * C.density)); ps = []; for (var i = 0; i < n; i++) { ps.push(mk()); } } function resize() { DPR = Math.min(window.devicePixelRatio || 1, 2); W = window.innerWidth; H = window.innerHeight; cv.width = Math.round(W * DPR); cv.height = Math.round(H * DPR); ctx.setTransform(DPR, 0, 0, DPR, 0, 0); initParticles(); } function frame() { t += 0.016; var sc = window.pageYOffset || 0; var d = sc - lastScroll; lastScroll = sc; var ad = Math.abs(d); var buf = 110; ctx.clearRect(0, 0, W, H); if (ready) { for (var i = 0; i < ps.length; i++) { var b = ps[i]; b.head += Math.sin(t * b.turnf + b.turnp) * 0.03 + Math.sin(t * b.turnf * 2.3 + b.turnp) * 0.015; var ex = 0; var ey = 0; if (b.x < buf) { ex = 1 - b.x / buf; } else if (b.x > W - buf) { ex = -(1 - (W - b.x) / buf); } if (b.y < buf) { ey = 1 - b.y / buf; } else if (b.y > H - buf) { ey = -(1 - (H - b.y) / buf); } if (ex || ey) { var toIn = Math.atan2(ey, ex); var diff = Math.atan2(Math.sin(toIn - b.head), Math.cos(toIn - b.head)); b.head += diff * 0.06 * Math.max(Math.abs(ex), Math.abs(ey)); } var flapRaw = Math.sin(t * b.ff + b.fp); var flap = Math.abs(flapRaw); var thrust = 0.55 + 0.45 * Math.max(0, flapRaw); var glide = 0.7 + 0.3 * Math.sin(t * b.glidef + b.glidep); if (ad > 0) { b.boost += Math.min(ad * 0.04 * C.startle, 2.2); b.head += (Math.random() - 0.5) * Math.min(ad * 0.008, 0.4) * C.startle; } b.boost *= 0.93; var spd = b.baseSpeed * thrust * glide * (1 + b.boost); var bob = Math.sin(t * b.bobf + b.bobp) * 0.5 + flapRaw * 0.6; b.x += Math.cos(b.head) * spd; b.y += Math.sin(b.head) * spd + bob; var m = b.size * 0.42; if (b.x < m) { b.x = m; b.head = Math.PI - b.head; } else if (b.x > W - m) { b.x = W - m; b.head = Math.PI - b.head; } if (b.y < m) { b.y = m; b.head = -b.head; } else if (b.y > H - m) { b.y = H - m; b.head = -b.head; } var tilt = Math.sin(b.head) * 0.18 + flapRaw * 0.06; var sx = 0.45 + 0.55 * flap; ctx.globalAlpha = Math.max(0, Math.min(1, b.a * C.opacity)); ctx.translate(b.x, b.y); ctx.rotate(tilt); ctx.scale(sx, 1); var w = b.size; var h = b.size / AR; ctx.drawImage(img, -w / 2, -h / 2, w, h); ctx.setTransform(DPR, 0, 0, DPR, 0, 0); } ctx.globalAlpha = 1; } requestAnimationFrame(frame); } var rt; function onResize() { clearTimeout(rt); rt = setTimeout(resize, 150); } resize(); requestAnimationFrame(frame); window.addEventListener("resize", onResize); window.addEventListener("load", resize); })();