feat: add shared retro arcade stylesheet

style.css

@@ -0,0 +1,74 @@
+* { margin: 0; padding: 0; box-sizing: border-box; }
+
+body {
+  background: #1a1a2e;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  min-height: 100vh;
+  font-family: 'Courier New', monospace;
+  color: #e0e0e0;
+}
+
+h1 {
+  font-size: 2rem;
+  margin-bottom: 12px;
+  color: #4ecca3;
+  letter-spacing: 4px;
+}
+
+.hud {
+  display: flex;
+  gap: 40px;
+  margin-bottom: 12px;
+  font-size: 1rem;
+  color: #a0a0c0;
+}
+
+.hud span { color: #4ecca3; font-weight: bold; }
+
+canvas {
+  border: 2px solid #4ecca3;
+  box-shadow: 0 0 20px rgba(78, 204, 163, 0.3);
+  display: block;
+}
+
+.overlay {
+  position: absolute;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 12px;
+}
+
+.overlay h2 { color: #4ecca3; font-size: 1.5rem; letter-spacing: 3px; }
+.overlay p  { color: #a0a0c0; font-size: 0.9rem; }
+
+.retro-btn {
+  background: transparent;
+  border: 2px solid #4ecca3;
+  color: #4ecca3;
+  padding: 10px 24px;
+  font-family: 'Courier New', monospace;
+  font-size: 0.9rem;
+  letter-spacing: 2px;
+  cursor: pointer;
+  text-transform: uppercase;
+}
+
+.retro-btn:hover { background: #4ecca3; color: #1a1a2e; }
+
+.menu-link {
+  position: absolute;
+  top: 16px;
+  left: 16px;
+  color: #4ecca3;
+  text-decoration: none;
+  font-size: 0.85rem;
+  letter-spacing: 2px;
+  opacity: 0.7;
+}
+
+.menu-link:hover { opacity: 1; }