fix style

frontend/src/App.css

@@ -196,6 +196,16 @@ body {
   color: var(--text-muted);
 }
 
+.challenge-detail-layout {
+  display: grid;
+  gap: 2rem;
+  grid-template-columns: minmax(0, 1fr) 300px;
+}
+
+#leaderboard-mobile {
+  display: none;
+}
+
 @media (max-width: 768px) {
   .nav {
     flex-direction: column;
@@ -223,6 +233,19 @@ body {
   .btn {
     width: 100%;
   }
+
+  /* Show mobile leaderboard, hide desktop sidebar */
+  #leaderboard-mobile {
+    display: block;
+  }
+
+  .challenge-sidebar {
+    display: none;
+  }
+
+  .challenge-detail-layout {
+    grid-template-columns: 1fr;
+  }
 }
 
 @media (max-width: 1024px) {

frontend/src/pages/ChallengeDetail.jsx

@@ -196,9 +196,31 @@ export default function ChallengeDetail() {
           </div>
         )}
 
-        <div style={{ display: 'grid', gap: '2rem', gridTemplateColumns: 'minmax(0, 1fr) 300px' }}>
+        {/* Leaderboard - Desktop: Sidebar, Mobile: Top */}
+        <div className="card" style={{ marginBottom: '2rem' }} id="leaderboard-mobile">
+          <h3 style={{ marginBottom: '1rem' }}>Leaderboard</h3>
+          {leaderboard.length === 0 ? (
+            <p style={{ color: 'var(--text-muted)', fontSize: '0.875rem' }}>No points yet</p>
+          ) : (
+            <div style={{ display: 'flex', flexDirection: 'column', gap: '0.75rem' }}>
+              {leaderboard.map((entry, index) => (
+                <div key={entry.id} style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center' }}>
+                  <div>
+                    <span style={{ marginRight: '0.5rem', color: 'var(--text-muted)' }}>{index + 1}.</span>
+                    <strong>{entry.username}</strong>
+                  </div>
+                  <span style={{ color: 'var(--primary)', fontWeight: 600 }}>
+                    {entry.validated_points} pts
+                  </span>
+                </div>
+              ))}
+            </div>
+          )}
+        </div>
+
+        <div className="challenge-detail-layout">
           {/* Main Content */}
-          <div>
+          <div className="challenge-main">
             {/* New Prediction */}
             <div className="card" style={{ marginBottom: '2rem' }}>
               <h3 style={{ marginBottom: '1rem' }}>Make a Prediction</h3>
@@ -272,8 +294,8 @@ export default function ChallengeDetail() {
             )}
           </div>
 
-          {/* Sidebar - Leaderboard */}
+          {/* Sidebar - Leaderboard (Desktop only) */}
-          <div>
+          <div className="challenge-sidebar">
             <div className="card">
               <h3 style={{ marginBottom: '1rem' }}>Leaderboard</h3>
               {leaderboard.length === 0 ? (

frontend/src/pages/ChallengeList.jsx

@@ -4,6 +4,7 @@ import api from '../api';
 
 export default function ChallengeList() {
   const [challenges, setChallenges] = useState([]);
+  const [pendingInvites, setPendingInvites] = useState([]);
   const [searchQuery, setSearchQuery] = useState('');
   const [showResults, setShowResults] = useState([]);
   const [loading, setLoading] = useState(true);
@@ -18,6 +19,10 @@ export default function ChallengeList() {
     try {
       const data = await api.getChallenges();
       setChallenges(data.challenges);
+      
+      // Filter out pending invitations
+      const pending = data.challenges.filter(c => c.participation_status === 'pending');
+      setPendingInvites(pending);
     } catch (err) {
       console.error('Failed to load challenges:', err);
     } finally {
@@ -25,6 +30,15 @@ export default function ChallengeList() {
     }
   };
 
+  const handleRespondToInvite = async (challengeId, status) => {
+    try {
+      await api.respondToChallenge(challengeId, status);
+      await loadChallenges();
+    } catch (err) {
+      alert('Failed to respond: ' + err.message);
+    }
+  };
+
   const handleSearch = (query) => {
     setSearchQuery(query);
     
@@ -84,6 +98,48 @@ export default function ChallengeList() {
       <div className="container">
         <h1 style={{ marginBottom: '2rem' }}>My Challenges</h1>
 
+        {/* Pending Invitations */}
+        {pendingInvites.length > 0 && (
+          <div className="card" style={{ marginBottom: '2rem', background: 'var(--bg-lighter)' }}>
+            <h3 style={{ marginBottom: '1rem' }}>📬 Pending Invitations</h3>
+            <div style={{ display: 'flex', flexDirection: 'column', gap: '1rem' }}>
+              {pendingInvites.map(challenge => (
+                <div key={challenge.id} style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', gap: '1rem', flexWrap: 'wrap' }}>
+                  <div style={{ display: 'flex', gap: '1rem', alignItems: 'center', flex: 1 }}>
+                    {challenge.cover_image_url && (
+                      <img 
+                        src={challenge.cover_image_url}
+                        alt={challenge.title}
+                        style={{ width: '40px', height: '60px', objectFit: 'cover', borderRadius: '0.25rem' }}
+                      />
+                    )}
+                    <div>
+                      <div style={{ fontWeight: 500 }}>{challenge.title}</div>
+                      <div style={{ fontSize: '0.875rem', color: 'var(--text-muted)' }}>
+                        Invited by {challenge.creator_username}
+                      </div>
+                    </div>
+                  </div>
+                  <div style={{ display: 'flex', gap: '0.5rem' }}>
+                    <button
+                      className="btn btn-success btn-sm"
+                      onClick={() => handleRespondToInvite(challenge.id, 'accepted')}
+                    >
+                      Accept
+                    </button>
+                    <button
+                      className="btn btn-danger btn-sm"
+                      onClick={() => handleRespondToInvite(challenge.id, 'rejected')}
+                    >
+                      Decline
+                    </button>
+                  </div>
+                </div>
+              ))}
+            </div>
+          </div>
+        )}
+
         {/* Search/Create */}
         <div style={{ marginBottom: '2rem', position: 'relative' }}>
           <input
@@ -141,13 +197,13 @@ export default function ChallengeList() {
         </div>
 
         {/* Challenge List */}
-        {challenges.length === 0 ? (
+        {challenges.filter(c => c.participation_status !== 'pending').length === 0 ? (
           <div className="card" style={{ textAlign: 'center', padding: '3rem' }}>
             <p style={{ color: 'var(--text-muted)' }}>No challenges yet. Search for a show above to create one!</p>
           </div>
         ) : (
           <div className="grid grid-2">
-            {challenges.map(challenge => (
+            {challenges.filter(c => c.participation_status !== 'pending').map(challenge => (
               <Link key={challenge.id} to={`/challenges/${challenge.id}`} style={{ textDecoration: 'none' }}>
                 <div className="card" style={{ height: '100%', display: 'flex', gap: '1rem' }}>
                   {challenge.cover_image_url && (