@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@400;500;600;700&display=swap');
        
        body { font-family: 'Poppins', sans-serif; background-color: #0f172a; color: #e2e8f0; margin: 0; padding: 40px 20px; }
        header { text-align: center; margin-bottom: 50px; }
        header h1 { font-size: 2.5rem; color: #38bdf8; margin-bottom: 10px; text-transform: uppercase; letter-spacing: 1.5px; text-shadow: 0 0 15px rgba(56, 189, 248, 0.4); }
        header p { color: #94a3b8; font-size: 1.1rem; }
        
        .container { max-width: 1000px; margin: 0 auto; }
        .grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 20px; }
        
        /* Tombol Gerbang Kelas */
        .gate-btn { background: #1e293b; border: 2px solid #334155; padding: 30px 20px; border-radius: 16px; color: #f8fafc; font-size: 1.2rem; font-weight: 600; cursor: pointer; transition: all 0.3s ease; display: flex; flex-direction: column; align-items: center; gap: 15px; }
        .gate-btn:hover { border-color: #38bdf8; transform: translateY(-5px); box-shadow: 0 10px 25px -5px rgba(56, 189, 248, 0.3); }
        .gate-icon { font-size: 3.5rem; }

        /* Kartu Materi */
        .card { background: #1e293b; padding: 25px; border-radius: 16px; border: 1px solid #334155; display: flex; flex-direction: column; transition: transform 0.2s; }
        .card:hover { transform: translateY(-3px); border-color: #10b981; }
        .card h3 { margin: 15px 0 10px; color: #f8fafc; }
        .card p { font-size: 0.9rem; color: #94a3b8; flex-grow: 1; line-height: 1.5; margin-bottom: 20px; }
        .badge { background: linear-gradient(135deg, #3b82f6, #8b5cf6); color: white; padding: 4px 12px; border-radius: 20px; font-size: 12px; align-self: flex-start; font-weight: bold; }
        .btn-masuk { padding: 12px; background: linear-gradient(to right, #10b981, #059669); color: white; text-align: center; text-decoration: none; border-radius: 8px; font-weight: bold; text-transform: uppercase; letter-spacing: 1px; }
        .btn-masuk:hover { background: linear-gradient(to right, #34d399, #10b981); }
        
        /* Navigasi */
        .back-btn { background: transparent; color: #38bdf8; border: 1px solid #38bdf8; padding: 8px 16px; border-radius: 8px; cursor: pointer; margin-bottom: 30px; display: inline-block; font-weight: bold; transition: 0.2s; }
        .back-btn:hover { background: #38bdf8; color: #0f172a; }
        
        .hidden { display: none !important; }