added the first space background : test

assets/app.js

@@ -1,4 +1,4 @@
-/* Progress line, reveals, diagram draw. No dependencies. */
+/* Progress line, reveals, diagram draw, space backdrop. No dependencies. */
 (function () {
   var root = document.documentElement;
   root.classList.add("anims");
@@ -43,6 +43,121 @@
     window.requestAnimationFrame(paint);
   }
 
+  function makeSpace() {
+    var space = document.createElement("div");
+    space.className = "space";
+    var w = window.innerWidth;
+    var h = window.innerHeight;
+
+    var starCount = w < 700 ? 80 : 150;
+    var stars = [];
+    for (var i = 0; i < starCount; i++) {
+      var s = document.createElement("div");
+      s.className = "space__star";
+      var size = 0.8 + Math.random() * 1.6;
+      var base = 0.2 + Math.random() * 0.55;
+      s.style.width = size + "px";
+      s.style.height = size + "px";
+      s.style.boxShadow = "0 0 " + (size * 2) + "px rgba(255,255,255," + (base * 0.5) + ")";
+      space.appendChild(s);
+      stars.push({
+        el: s,
+        x: Math.random() * w,
+        y: Math.random() * h,
+        vx: (Math.random() - 0.5) * 1.4,
+        vy: (Math.random() - 0.5) * 1.4,
+        base: base,
+        phase: Math.random() * Math.PI * 2,
+        twinkle: 0.3 + Math.random() * 0.5
+      });
+    }
+
+    var nebulae = [
+      { x: 0.18, y: 0.30, rx: 38, ry: 22, angle: -20, c1: "120,150,255", c2: "80,200,200", strength: 0.5 },
+      { x: 0.78, y: 0.22, rx: 30, ry: 44, angle: 160, c1: "180,120,255", c2: "240,150,120", strength: 0.4 },
+      { x: 0.55, y: 0.78, rx: 46, ry: 26, angle: 70, c1: "150,210,255", c2: "120,240,180", strength: 0.45 }
+    ];
+
+    nebulae.forEach(function (n, idx) {
+      var el = document.createElement("div");
+      el.className = "space__nebula";
+      el.style.width = (n.rx * 2.6) + "%";
+      el.style.height = (n.ry * 2.6) + "%";
+      el.style.left = (n.x * 100 - n.rx * 1.3) + "%";
+      el.style.top = (n.y * 100 - n.ry * 1.3) + "%";
+      el.style.background =
+        "radial-gradient(ellipse at center, rgba(" + n.c1 + "," + (0.22 * n.strength) +
+        "), rgba(" + n.c2 + "," + (0.16 * n.strength) + "), transparent 70%)";
+      n.el = el;
+      n.seed = idx * 19.1;
+      n.amp = 1.6;
+      space.appendChild(el);
+    });
+
+    document.body.appendChild(space);
+
+    function place(star) {
+      star.el.style.transform =
+        "translate3d(" + star.x.toFixed(1) + "px," + star.y.toFixed(1) + "px,0)";
+    }
+
+    function placeNebula(n, t) {
+      var dx = Math.sin(t * 0.25 + n.seed) * n.amp;
+      var dy = Math.cos(t * 0.20 + n.seed * 0.7) * n.amp;
+      n.el.style.transform =
+        "translate3d(" + dx.toFixed(2) + "vw," + dy.toFixed(2) + "vh,0) rotate(" + n.angle + "deg)";
+      n.el.style.opacity = 0.09 + 0.03 * Math.sin(t * 0.4 + n.seed);
+    }
+
+    if (reduce) {
+      for (var k = 0; k < stars.length; k++) {
+        place(stars[k]);
+        stars[k].el.style.opacity = stars[k].base;
+      }
+      nebulae.forEach(function (n) { placeNebula(n, 0); });
+      window.addEventListener("resize", function () {
+        w = window.innerWidth;
+        h = window.innerHeight;
+        for (var k = 0; k < stars.length; k++) {
+          if (stars[k].x > w) stars[k].x = Math.random() * w;
+          if (stars[k].y > h) stars[k].y = Math.random() * h;
+          place(stars[k]);
+        }
+      }, { passive: true });
+      return;
+    }
+
+    var last = performance.now();
+    function frame(now) {
+      var dt = Math.min((now - last) / 1000, 0.1);
+      last = now;
+      var t = now * 0.00005;
+
+      for (var k = 0; k < stars.length; k++) {
+        var st = stars[k];
+        st.x += st.vx * dt;
+        st.y += st.vy * dt;
+        if (st.x < -4) st.x += w + 8;
+        else if (st.x > w + 4) st.x -= w + 8;
+        if (st.y < -4) st.y += h + 8;
+        else if (st.y > h + 4) st.y -= h + 8;
+        place(st);
+        st.el.style.opacity =
+          st.base * (0.65 + 0.35 * Math.sin(t * st.twinkle * 12 + st.phase));
+      }
+
+      for (var j = 0; j < nebulae.length; j++) placeNebula(nebulae[j], t);
+
+      requestAnimationFrame(frame);
+    }
+    requestAnimationFrame(frame);
+
+    window.addEventListener("resize", function () {
+      w = window.innerWidth;
+      h = window.innerHeight;
+    }, { passive: true });
+  }
+
   try {
     [].forEach.call(groups, function (group) {
       [].forEach.call(group.children, function (item, i) {
@@ -57,6 +172,7 @@
       window.addEventListener("resize", queue, { passive: true });
       paint();
     }
+    makeSpace();
   } catch (err) {
     root.classList.remove("anims");
   }