:root {
    --primary: #2c3e50;
    --accent: #3498db;
    --success: #27ae60;
    --error: #c0392b;
    --bg: #ecf0f1;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg);
    color: var(--primary);
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
}

header {
    background-color: var(--primary);
    color: white;
    width: 100%;
    text-align: center;
    padding: 1rem 0;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

nav {
    margin: 20px 0;
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    justify-content: center;
}

button {
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1rem;
    background-color: white;
    color: var(--primary);
    transition: all 0.2s;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 6px rgba(0,0,0,0.15);
}

button.active {
    background-color: var(--accent);
    color: white;
}

#game-container {
    background: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    width: 90%;
    max-width: 600px;
    text-align: center;
    min-height: 300px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}

/* Flashcard Styles */
.card {
    perspective: 1000px;
    width: 100%;
    height: 200px;
    cursor: pointer;
}

.card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.6s;
    transform-style: preserve-3d;
    display: flex;
    justify-content: center;
    align-items: center;
}

.card.flipped .card-inner {
    transform: rotateY(180deg);
}

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5rem;
    border-radius: 10px;
    border: 2px solid var(--accent);
    background: white;
    padding: 20px;
    box-sizing: border-box;
}

.card-front {
    background-color: #fff;
    color: var(--primary);
}

.card-back {
    background-color: var(--accent);
    color: white;
    transform: rotateY(180deg);
}

/* Quiz Styles */
.options-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
    width: 100%;
    margin-top: 20px;
}

.option-btn {
    background-color: #f8f9fa;
    border: 1px solid #ddd;
    padding: 15px;
    width: 100%;
}

/* Input Styles */
input[type="text"] {
    padding: 10px;
    font-size: 1.2rem;
    border: 2px solid #ddd;
    border-radius: 5px;
    width: 80%;
    margin-bottom: 15px;
}

.next-btn {
    background-color: var(--primary);
    color: white;
    margin-top: 20px;
}

/* Feedback */
.correct { background-color: var(--success) !important; color: white !important; }
.wrong { background-color: var(--error) !important; color: white !important; }

#result-message {
    margin-top: 20px;
    font-weight: bold;
    font-size: 1.2rem;
    height: 30px;
}