feat: add page-flip animation, click and swipe navigation to deck viewer

Click left/right halves to navigate. Swipe on touch devices. 3D
perspective page-flip animation on transitions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

components/sponsorship-flipbook.tsx

@@ -1,45 +1,108 @@
 "use client"
 
-import { useState } from "react"
+import { useState, useRef, useCallback } from "react"
 import Image from "next/image"
 import { ChevronLeft, ChevronRight } from "lucide-react"
 import { Button } from "@/components/ui/button"
 
 const TOTAL_SLIDES = 12
+const SWIPE_THRESHOLD = 50
 
 export default function SponsorshipFlipbook() {
   const [currentSlide, setCurrentSlide] = useState(0)
+  const [isFlipping, setIsFlipping] = useState(false)
+  const [flipDirection, setFlipDirection] = useState<"left" | "right">("left")
+  const touchStartX = useRef(0)
+  const touchEndX = useRef(0)
 
-  const prevSlide = () => setCurrentSlide((s) => Math.max(0, s - 1))
-  const nextSlide = () => setCurrentSlide((s) => Math.min(TOTAL_SLIDES - 1, s + 1))
+  const goTo = useCallback(
+    (direction: "prev" | "next") => {
+      if (isFlipping) return
+      if (direction === "prev" && currentSlide === 0) return
+      if (direction === "next" && currentSlide >= TOTAL_SLIDES - 1) return
+
+      setFlipDirection(direction === "next" ? "left" : "right")
+      setIsFlipping(true)
+
+      setTimeout(() => {
+        setCurrentSlide((s) =>
+          direction === "next"
+            ? Math.min(TOTAL_SLIDES - 1, s + 1)
+            : Math.max(0, s - 1)
+        )
+        setIsFlipping(false)
+      }, 400)
+    },
+    [currentSlide, isFlipping]
+  )
+
+  const handleClick = (e: React.MouseEvent<HTMLDivElement>) => {
+    const rect = e.currentTarget.getBoundingClientRect()
+    const clickX = e.clientX - rect.left
+    if (clickX < rect.width / 2) {
+      goTo("prev")
+    } else {
+      goTo("next")
+    }
+  }
+
+  const handleTouchStart = (e: React.TouchEvent) => {
+    touchStartX.current = e.touches[0].clientX
+    touchEndX.current = e.touches[0].clientX
+  }
+
+  const handleTouchMove = (e: React.TouchEvent) => {
+    touchEndX.current = e.touches[0].clientX
+  }
+
+  const handleTouchEnd = () => {
+    const diff = touchStartX.current - touchEndX.current
+    if (Math.abs(diff) > SWIPE_THRESHOLD) {
+      goTo(diff > 0 ? "next" : "prev")
+    }
+  }
 
   return (
     <div className="flex flex-col items-center gap-4">
-      <div className="relative w-full overflow-hidden rounded-xl border border-border shadow-lg bg-black">
       <div
-          className="flex transition-transform duration-500 ease-in-out"
-          style={{ transform: `translateX(-${currentSlide * 100}%)` }}
+        className="relative w-full overflow-hidden rounded-xl border border-border shadow-lg bg-black cursor-pointer select-none"
+        style={{ perspective: "1200px" }}
+        onClick={handleClick}
+        onTouchStart={handleTouchStart}
+        onTouchMove={handleTouchMove}
+        onTouchEnd={handleTouchEnd}
+      >
+        <div
+          className="w-full"
+          style={{
+            transformOrigin:
+              flipDirection === "left" ? "left center" : "right center",
+            transition: isFlipping
+              ? "transform 0.4s ease-in-out, opacity 0.4s ease-in-out"
+              : "none",
+            transform: isFlipping
+              ? `rotateY(${flipDirection === "left" ? "-90deg" : "90deg"})`
+              : "rotateY(0deg)",
+            opacity: isFlipping ? 0 : 1,
+          }}
         >
-          {Array.from({ length: TOTAL_SLIDES }, (_, i) => (
-            <div key={i} className="w-full flex-shrink-0">
           <Image
-                src={`/slides/slide-${String(i + 1).padStart(2, "0")}.jpg`}
-                alt={`Sponsorship deck slide ${i + 1}`}
+            src={`/slides/slide-${String(currentSlide + 1).padStart(2, "0")}.jpg`}
+            alt={`Sponsorship deck slide ${currentSlide + 1}`}
             width={1200}
             height={675}
             className="w-full h-auto"
-                priority={i <= 1}
+            priority
+            draggable={false}
           />
         </div>
-          ))}
-        </div>
       </div>
 
       <div className="flex items-center gap-4">
         <Button
           variant="outline"
           size="icon"
-          onClick={prevSlide}
+          onClick={() => goTo("prev")}
           disabled={currentSlide === 0}
           aria-label="Previous slide"
         >
@@ -51,7 +114,7 @@ export default function SponsorshipFlipbook() {
         <Button
           variant="outline"
           size="icon"
-          onClick={nextSlide}
+          onClick={() => goTo("next")}
           disabled={currentSlide >= TOTAL_SLIDES - 1}
           aria-label="Next slide"
         >