* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    background-color: #f3f4f6;
    min-height: 100vh;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.logo {
    background-color: #1d4ed8;
    color: white;
    padding: 20px 40px;
    border-radius: 10px;
    text-align: center;
    margin-bottom: 30px;
}

.logo h1 {
    font-size: 32px;
    font-weight: bold;
    margin-bottom: 5px;
}

.logo p {
    font-size: 14px;
}

.bingo-header {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 2px;
    margin-bottom: 20px;
}

.bingo-letter {
    background-color: #1d4ed8;
    color: white;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    font-weight: bold;
}

.bingo-board {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 2px;
    background-color: white;
    padding: 20px;
    border: 2px solid #d1d5db;
    border-radius: 10px;
    margin-bottom: 30px;
}

.bingo-cell {
    width: 60px;
    height: 60px;
    border: 1px solid #d1d5db;
    background-color: white;
    cursor: pointer;
    font-size: 16px;
    font-weight: 600;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}

.bingo-cell:hover {
    background-color: #f3f4f6;
}

.bingo-cell.marked {
    background-color: #10b981;
    color: white;
}

.bingo-cell.center {
    background-color: #1d4ed8;
    color: white;
    font-size: 12px;
}

.bingo-cell.center.marked {
    background-color: #1e40af;
}

.controls {
    display: flex;
    gap: 20px;
    margin-bottom: 30px;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 14px;
}

.btn-undo {
    background-color: #f59e0b;
    color: white;
}

.btn-undo:hover:not(:disabled) {
    background-color: #d97706;
}

.btn-undo:disabled {
    background-color: #d1d5db;
    color: #6b7280;
    cursor: not-allowed;
}

.btn-reset {
    background-color: #ef4444;
    color: white;
}

.btn-reset:hover {
    background-color: #dc2626;
}

.game-info {
    text-align: center;
    color: #6b7280;
    max-width: 500px;
}

.game-info p {
    margin-bottom: 10px;
}

.game-info .highlight {
    font-weight: 600;
    color: #374151;
}

.instructions {
    background-color: #dbeafe;
    padding: 20px;
    border-radius: 10px;
    margin-top: 30px;
    max-width: 400px;
    text-align: center;
}

.instructions h3 {
    color: #1e40af;
    margin-bottom: 15px;
    font-size: 16px;
}

.instructions ul {
    list-style: none;
    color: #1e40af;
}

.instructions li {
    margin-bottom: 8px;
    font-size: 14px;
}

.counter {
    font-weight: 600;
    margin-top: 15px;
    color: #374151;
}