feat(web): WarioWare-style transition between rounds

- RoundTransition overlay: fullscreen colored wipe-in, spinning sunburst,
  big bouncing "QUESTION N" + "PRÊT ?!", then wipe-out (Framer Motion)
- store: roundKey counter incremented on round:start
- rendered at RoomPage, keyed by roundKey so it plays once per round

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/web/src/components/round-transition.tsx

@@ -0,0 +1,80 @@
+import { useEffect, useState } from "react"
+import { createPortal } from "react-dom"
+import { AnimatePresence, motion } from "framer-motion"
+
+const VISIBLE_MS = 1100 // durée d'affichage avant le wipe de sortie
+
+/**
+ * Transition "WarioWare" jouée entre les manches : wipe coloré plein écran,
+ * sunburst qui tourne, gros numéro de question qui rebondit, puis sortie.
+ * Montée avec une `key` qui change → rejoue à chaque manche.
+ */
+export function RoundTransition({ index }: { index: number }) {
+  const [show, setShow] = useState(true)
+
+  useEffect(() => {
+    const t = setTimeout(() => setShow(false), VISIBLE_MS)
+    return () => clearTimeout(t)
+  }, [])
+
+  return createPortal(
+    <AnimatePresence>
+      {show && (
+        <motion.div
+          key="round-transition"
+          className="pointer-events-auto fixed inset-0 z-50 flex items-center justify-center overflow-hidden bg-gradient-to-br from-fuchsia-500 via-purple-600 to-indigo-700"
+          initial={{ clipPath: "inset(0 0 100% 0)" }}
+          animate={{ clipPath: "inset(0 0 0% 0)" }}
+          exit={{
+            clipPath: "inset(100% 0 0 0)",
+            transition: { duration: 0.3, ease: "easeIn" },
+          }}
+          transition={{ duration: 0.25, ease: "easeOut" }}
+        >
+          <motion.div
+            aria-hidden
+            className="absolute size-[220vmax] opacity-60"
+            style={{
+              backgroundImage:
+                "repeating-conic-gradient(rgba(255,255,255,0.12) 0deg 12deg, transparent 12deg 24deg)",
+            }}
+            animate={{ rotate: 360 }}
+            transition={{ duration: 7, repeat: Infinity, ease: "linear" }}
+          />
+
+          <motion.div
+            className="relative flex flex-col items-center"
+            initial={{ scale: 0, rotate: -12 }}
+            animate={{ scale: [0, 1.25, 1], rotate: [-12, 6, 0] }}
+            transition={{
+              duration: 0.5,
+              times: [0, 0.6, 1],
+              delay: 0.12,
+              ease: "easeOut",
+            }}
+          >
+            <span className="font-heading text-2xl font-black tracking-[0.35em] text-white uppercase drop-shadow">
+              Question
+            </span>
+            <motion.span
+              className="font-heading text-[26vmin] leading-none font-black text-yellow-300 drop-shadow-[0_5px_0_rgba(0,0,0,0.25)]"
+              animate={{ scale: [1, 1.07, 1] }}
+              transition={{ duration: 0.4, repeat: Infinity, repeatType: "reverse" }}
+            >
+              {index + 1}
+            </motion.span>
+            <motion.span
+              initial={{ opacity: 0, y: 10 }}
+              animate={{ opacity: 1, y: 0 }}
+              transition={{ delay: 0.5 }}
+              className="font-heading -rotate-3 text-3xl font-black text-white italic"
+            >
+              PRÊT ?!
+            </motion.span>
+          </motion.div>
+        </motion.div>
+      )}
+    </AnimatePresence>,
+    document.body
+  )
+}

apps/web/src/pages/room.tsx

@@ -7,12 +7,14 @@ import { GameEndView } from "@/components/game-end-view"
 import { PlayerCards } from "@/components/player-cards"
 import { RoomCode } from "@/components/room-code"
 import { Boom } from "@/components/boom"
+import { RoundTransition } from "@/components/round-transition"
 
 export function RoomPage({ code }: { code: string }) {
   const snapshot = useRoomStore((s) => s.snapshot)
   const playerId = useRoomStore((s) => s.playerId)
   const connected = useRoomStore((s) => s.connected)
   const boomKey = useRoomStore((s) => s.boomKey)
+  const roundKey = useRoomStore((s) => s.roundKey)
   const voteProgress = useRoomStore((s) => s.voteProgress)
 
   // Pas de snapshot pour ce code (accès direct / refresh) : retour à l'accueil.
@@ -61,6 +63,9 @@ export function RoomPage({ code }: { code: string }) {
       </div>
 
       {boomKey > 0 && <Boom key={boomKey} />}
+      {roundKey > 0 && (
+        <RoundTransition key={roundKey} index={snapshot.currentRound} />
+      )}
     </div>
   )
 }

apps/web/src/store/room.ts

@@ -39,6 +39,8 @@ interface RoomState {
   finalScores: PlayerScore[] | null
   /** Compteur d'explosions : incrémenté à chaque fin de manche au timer (boom à 0). */
   boomKey: number
+  /** Compteur de manches : incrémenté à chaque round:start (transition WarioWare). */
+  roundKey: number
 
   createRoom: (playerName: string) => Promise<RoomCreatedPayload>
   joinRoom: (roomCode: string, playerName: string) => Promise<RoomCreatedPayload>
@@ -61,6 +63,7 @@ export const useRoomStore = create<RoomState>((set, get) => ({
   myChoiceIndex: null,
   finalScores: null,
   boomKey: 0,
+  roundKey: 0,
 
   createRoom: (playerName) =>
     new Promise((resolve, reject) => {
@@ -131,6 +134,7 @@ export const useRoomStore = create<RoomState>((set, get) => ({
       myChoiceIndex: null,
       finalScores: null,
       boomKey: 0,
+      roundKey: 0,
     }),
 }))
 
@@ -141,7 +145,7 @@ socket.on("room:state", (snapshot) => useRoomStore.setState({ snapshot }))
 socket.on("error", (error) => useRoomStore.setState({ lastError: error }))
 
 socket.on("round:start", (payload) =>
-  useRoomStore.setState({
+  useRoomStore.setState((s) => ({
     round: {
       type: payload.type,
       djId: payload.djId,
@@ -151,7 +155,8 @@ socket.on("round:start", (payload) =>
     voteProgress: null,
     reveal: null,
     myChoiceIndex: null,
-  })
+    roundKey: s.roundKey + 1,
+  }))
 )
 socket.on("round:voteAck", (voteProgress) =>
   useRoomStore.setState({ voteProgress })