style(site): pushable 3D neon buttons (lifting face + ::before wall, spring curves)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

site/assets/css/style.css

@@ -354,48 +354,81 @@ section[id] {
   color: var(--fitme-accent);
 }
 
-/* ── 3D neon extrusion on hover ────────────────────────────────────────────────
-   The button lifts off the "wall" toward the viewer; the faces it leaves behind
-   (the extruded sides) are drawn with stacked hard shadows in the brand colour
-   and lit like neon tubes (glow on top). Colours come from the gym's brand
-   tokens, so each gym glows in its own colour. */
+/* ── 3D "pushable" neon button ─────────────────────────────────────────────────
+   The element itself is the face. On hover it lifts straight up by --depth and
+   a ::before strip, hanging off the face's bottom edge, grows to fill the gap:
+   that strip is the extruded wall, lit in the brand colour with a neon glow
+   (darker at both ends like a rounded edge). Only transform / opacity animate
+   (compositor-only). Lift springs (overshoot curve), release is slow, press is
+   instant — same feel as a physical key. Colours come from --fitme-accent, so
+   each gym glows in its own colour. */
+:where(.site-btn, .gym-switch-btn) { position: relative; }
+
 .site-btn,
 .gym-switch-btn {
-  --neon: color-mix(in srgb, var(--fitme-accent) 70%, #fff);
-  --neon-edge: var(--fitme-accent-dark);
-  --depth: 4px;
+  --depth: 5px;
+  --bw: 0px;                       /* the element's own border, so the wall starts below it */
+  --wall-hi: color-mix(in srgb, var(--fitme-accent) 70%, #fff);
+  --wall: var(--fitme-accent);
+  --wall-lo: color-mix(in srgb, var(--fitme-accent) 45%, #000);
+}
+.site-btn.sb-line,
+.site-btn.sb-ghost { --bw: 2px; }
+
+.site-btn::before,
+.gym-switch-btn::before {
+  content: "";
+  position: absolute;
+  left: 0;
+  right: 0;
+  top: calc(100% + var(--bw));
+  height: var(--depth);
+  border-radius: 0 0 var(--fitme-radius) var(--fitme-radius);
+  background: linear-gradient(to right, var(--wall-lo) 0%, var(--wall) 10%, var(--wall-hi) 50%, var(--wall) 90%, var(--wall-lo) 100%);
+  box-shadow: 0 2px 14px 1px rgba(var(--fitme-accent-rgb), .6);
+  transform: scaleY(0);
+  transform-origin: top;
+  pointer-events: none;
 }
 
 @media (hover: hover) and (prefers-reduced-motion: no-preference) {
   .site-btn,
   .gym-switch-btn {
-    transition: transform .18s ease, box-shadow .18s ease, background var(--fitme-transition), color var(--fitme-transition);
+    will-change: transform;
+    transition: transform 600ms cubic-bezier(.3, .7, .4, 1), box-shadow 600ms cubic-bezier(.3, .7, .4, 1),
+                background var(--fitme-transition), color var(--fitme-transition);
+  }
+  .site-btn::before,
+  .gym-switch-btn::before {
+    transition: transform 600ms cubic-bezier(.3, .7, .4, 1);
   }
 
   .site-btn:hover,
   .site-btn:focus-visible,
   .gym-switch-btn:hover,
   .gym-switch-btn:focus-visible {
-    transform: translate(calc(var(--depth) * -1), calc(var(--depth) * -1));
-    /* The extruded sides ARE the neon: three lit steps (bright at the face,
-       settling toward the wall) and a soft glow round the whole solid. The
-       face itself stays plain — no second outline, so nothing reads as a copy. */
-    box-shadow:
-      inset 1px 1px 0 rgba(var(--fitme-accent-rgb), .55),     /* lit top-left bevel on the face */
-      1px 1px 0 var(--neon),
-      2px 2px 0 var(--fitme-accent),
-      3px 3px 0 color-mix(in srgb, var(--fitme-accent) 75%, #000),
-      4px 4px 0 color-mix(in srgb, var(--fitme-accent) 50%, #000),
-      0 0 18px 3px rgba(var(--fitme-accent-rgb), .4),
-      4px 4px 22px 2px rgba(var(--fitme-accent-rgb), .3);
+    transform: translateY(calc(var(--depth) * -1));
+    box-shadow: 0 0 18px 2px rgba(var(--fitme-accent-rgb), .35);
+    transition-duration: 250ms, 250ms, var(--fitme-transition), var(--fitme-transition);
+    transition-timing-function: cubic-bezier(.3, .7, .4, 1.5);
+  }
+  .site-btn:hover::before,
+  .site-btn:focus-visible::before,
+  .gym-switch-btn:hover::before,
+  .gym-switch-btn:focus-visible::before {
+    transform: scaleY(1);
+    transition: transform 250ms cubic-bezier(.3, .7, .4, 1.5);
   }
 
   .site-btn:active,
   .gym-switch-btn:active {
-    transform: translate(-1px, -1px);
-    box-shadow:
-      1px 1px 0 var(--neon),
-      0 0 10px 1px rgba(var(--fitme-accent-rgb), .5);
+    transform: translateY(-1px);
+    transition-duration: 34ms;
+  }
+  .site-btn:active::before,
+  .gym-switch-btn:active::before {
+    transform: scaleY(.2);
+    transition-duration: 34ms;
   }
 }