補上先攻勾選顯示並更新 README

src/pages/ScoreboardPage.tsx

@@ -276,6 +276,7 @@ export function ScoreboardPage({
             onSwapTeams={onSwapMatchup}
             score={scoreState.scoreLeft}
             serviceCourt={scoreState.serving === 'left' ? servingCourt : null}
+            showServingPrompt={scoreState.serving === null}
             team={leftTeam}
             teamSlot="top"
           />
@@ -303,6 +304,7 @@ export function ScoreboardPage({
             onSwapTeams={onSwapMatchup}
             score={scoreState.scoreRight}
             serviceCourt={scoreState.serving === 'right' ? servingCourt : null}
+            showServingPrompt={scoreState.serving === null}
             team={rightTeam}
             teamSlot="bottom"
           />
@@ -379,6 +381,7 @@ type ScoreboardTeamPanelProps = {
   onSwapTeams: () => void
   score: number
   serviceCourt: CourtSide | null
+  showServingPrompt: boolean
   team: GroupTeam | null
   teamSlot: 'top' | 'bottom'
 }
@@ -395,6 +398,7 @@ function ScoreboardTeamPanel({
   onSwapTeams,
   score,
   serviceCourt,
+  showServingPrompt,
   team,
   teamSlot,
 }: ScoreboardTeamPanelProps) {
@@ -450,13 +454,22 @@ function ScoreboardTeamPanel({
   const serveBar = (
     <button
       className={
-        currentServer && !canArrangeMatch ? 'serve-lane serve-lane-locked' : 'serve-lane'
+        currentServer && !canArrangeMatch
+          ? 'serve-lane serve-lane-locked'
+          : showServingPrompt
+            ? 'serve-lane serve-lane-prompt'
+            : 'serve-lane'
       }
       disabled={!canArrangeMatch || !team}
       type="button"
       onClick={onSetServing}
     >
-      <span className="serve-lane-box" />
+      {showServingPrompt ? (
+        <span aria-hidden="true" className="serve-lane-arrow">
+          {teamSlot === 'top' ? '↓' : '↑'}
+        </span>
+      ) : null}
+      <span className={currentServer ? 'serve-lane-box serve-lane-box-checked' : 'serve-lane-box'} />
       <span>先攻</span>
       {currentServer ? (
         <small>