body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #eef2f5;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    user-select: none;
}

.container {
    background: white;
    width: 100%;
    max-width: 420px;
    height: 100%;
    max-height: 800px;
    position: relative;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
    display: flex;
    flex-direction: column;
}

.screen {
    display: none;
    flex-direction: column;
    align-items: center; /* Rata tengah secara horizontal */
    padding: 20px;
    box-sizing: border-box;
    height: 100%;
    width: 100%;
}

.screen.active { display: flex; }

/* Judul & Teks */
h1 { color: #4a90e2; font-size: 2.5rem; margin-top: 50px; margin-bottom: 10px; }
.subtitle { color: #7f8c8d; margin-bottom: 30px; }

/* Menu Grid */
.mode-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    width: 100%;
}

.mode-btn {
    background: white;
    border: 2px solid #4a90e2;
    color: #4a90e2;
    padding: 15px;
    font-size: 1.1rem;
    border-radius: 12px;
    cursor: pointer;
    font-weight: bold;
    transition: 0.2s;
}

.mode-btn:active { transform: scale(0.95); background: #357abd; color: white; }

/* TOMBOL BACK BARU */
.back-btn {
    align-self: flex-start; /* Geser ke kiri mentok */
    background: transparent;
    border: none;
    color: #95a5a6;
    font-size: 1rem;
    cursor: pointer;
    margin-bottom: 15px;
    margin-top: 10px;
    font-weight: bold;
}
.back-btn:hover { color: #e74c3c; }

/* Tampilan Game */
.top-bar {
    width: 100%;
    display: flex;
    justify-content: space-between;
    margin-bottom: 20px;
}

.level-badge, .timer-badge {
    background: #4a90e2;
    color: white;
    padding: 8px 15px;
    border-radius: 20px;
    font-weight: bold;
    font-size: 0.9rem;
}
.timer-badge { background: #e74c3c; }

.score-display {
    font-size: 1.5rem;
    color: #2c3e50;
    font-weight: bold;
    margin-bottom: 20px;
}

.question-box {
    background: #ecf0f1;
    width: 100%;
    padding: 40px 0;
    text-align: center;
    border-radius: 15px;
    margin-bottom: 30px;
    box-shadow: inset 0 2px 5px rgba(0,0,0,0.05);
}

.question-box h2 { font-size: 3rem; margin: 0; color: #2c3e50; }

.options {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    width: 100%;
}

.option-btn {
    background: white;
    border: 2px solid #bdc3c7;
    color: #2c3e50;
    padding: 20px;
    font-size: 1.8rem;
    border-radius: 12px;
    cursor: pointer;
    font-weight: bold;
}

.option-btn:active { background: #4a90e2; color: white; border-color: #4a90e2; }

/* Game Over */
.big-score { font-size: 4rem; margin: 10px 0; color: #2ecc71; }
.restart-btn {
    background: #2c3e50;
    color: white;
    padding: 15px 40px;
    border: none;
    border-radius: 50px;
    font-size: 1.2rem;
    margin-top: 20px;
    cursor: pointer;
}