Add scroll hint

packages/skin-database/app/(modern)/scroll/Events.ts

@@ -97,4 +97,7 @@ export type UserEvent =
   | {
       type: "menu_click";
       menuItem: string;
+    }
+  | {
+      type: "scroll_hint_shown";
     };

packages/skin-database/app/(modern)/scroll/SkinScroller.tsx

@@ -3,6 +3,7 @@
 import { useState, useLayoutEffect, useEffect } from "react";
 import SkinPage from "./SkinPage";
 import { logUserEvent } from "./Events";
+import { useScrollHint } from "./useScrollHint";
 
 export type ClientSkin = {
   screenshotUrl: string;
@@ -30,6 +31,25 @@ export default function SkinScroller({
   const [visibleSkinIndex, setVisibleSkinIndex] = useState(0);
   const [fetching, setFetching] = useState(false);
   const [containerRef, setContainerRef] = useState<HTMLDivElement | null>(null);
+  const [hasEverScrolled, setHasEverScrolled] = useState(false);
+
+  // Track if user has ever scrolled to another skin
+  useEffect(() => {
+    if (visibleSkinIndex > 0) {
+      setHasEverScrolled(true);
+    }
+  }, [visibleSkinIndex]);
+
+  // Show scroll hint only if user has never scrolled to another skin
+  useScrollHint({
+    containerRef,
+    enabled: visibleSkinIndex === 0 && !hasEverScrolled,
+    onHintShown: () => {
+      logUserEvent(sessionId, {
+        type: "scroll_hint_shown",
+      });
+    },
+  });
 
   useLayoutEffect(() => {
     if (containerRef == null) {

packages/skin-database/app/(modern)/scroll/useScrollHint.ts

@@ -0,0 +1,99 @@
+import { useEffect } from "react";
+
+type UseScrollHintOptions = {
+  containerRef: HTMLDivElement | null;
+  enabled: boolean;
+  delayMs?: number;
+  scrollAmount?: number;
+  animationDuration?: number;
+  onHintShown?: () => void;
+};
+
+/**
+ * A hook that provides a gentle scroll hint animation to encourage user interaction.
+ * After a delay, if the user hasn't scrolled, it will scroll down slightly and bounce back.
+ */
+export function useScrollHint({
+  containerRef,
+  enabled,
+  delayMs = 5000,
+  scrollAmount = 80,
+  animationDuration = 1000,
+  onHintShown,
+}: UseScrollHintOptions) {
+  useEffect(() => {
+    if (containerRef == null || !enabled) {
+      return;
+    }
+
+    const hintTimer = setTimeout(() => {
+      if (!enabled || containerRef.scrollTop !== 0) {
+        return;
+      }
+
+      const startScrollTop = containerRef.scrollTop;
+      const startTime = Date.now();
+
+      // Temporarily disable scroll snap for smooth animation
+      const originalScrollSnapType = containerRef.style.scrollSnapType;
+      containerRef.style.scrollSnapType = "none";
+
+      const animate = () => {
+        const elapsed = Date.now() - startTime;
+        const progress = Math.min(elapsed / animationDuration, 1);
+
+        // Bouncy easing function - overshoots and bounces back
+        const easeOutBounce = (t: number) => {
+          const n1 = 7.5625;
+          const d1 = 2.75;
+          if (t < 1 / d1) {
+            return n1 * t * t;
+          } else if (t < 2 / d1) {
+            return n1 * (t -= 1.5 / d1) * t + 0.75;
+          } else if (t < 2.5 / d1) {
+            return n1 * (t -= 2.25 / d1) * t + 0.9375;
+          } else {
+            return n1 * (t -= 2.625 / d1) * t + 0.984375;
+          }
+        };
+
+        // Create a bounce effect: scroll down quickly, then bounce back
+        let offset;
+        if (progress < 0.4) {
+          // First 40%: scroll down quickly
+          const t = progress / 0.4;
+          offset = scrollAmount * t * t; // Quadratic ease-in
+        } else {
+          // Last 60%: bounce back with overshoot
+          const t = (progress - 0.4) / 0.6;
+          offset = scrollAmount * (1 - easeOutBounce(t));
+        }
+
+        containerRef.scrollTop = startScrollTop + offset;
+
+        if (progress < 1) {
+          requestAnimationFrame(animate);
+        } else {
+          // Ensure we end exactly where we started
+          containerRef.scrollTop = startScrollTop;
+          // Re-enable scroll snap
+          containerRef.style.scrollSnapType = originalScrollSnapType;
+        }
+      };
+
+      animate();
+      onHintShown?.();
+    }, delayMs);
+
+    return () => {
+      clearTimeout(hintTimer);
+    };
+  }, [
+    containerRef,
+    enabled,
+    delayMs,
+    scrollAmount,
+    animationDuration,
+    onHintShown,
+  ]);
+}