.letter-tile {
    width: 40px;
    height: 40px;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    font-weight: bold;
    color: #334155;
    transition: all 0.3s ease;
}

.letter-tile.filled {
    background-color: #e0f2fe;
    border-color: #3b82f6;
}

.keyboard-btn {
    background-color: #f1f5f9;
    border: none;
    border-radius: 8px;
    padding: 10px 0;
    font-size: 16px;
    font-weight: 600;
    color: #334155;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

.keyboard-btn:hover:not(:disabled) {
    background-color: #e2e8f0;
    transform: translateY(-2px);
}

.keyboard-btn:active:not(:disabled) {
    transform: translateY(0);
}

.keyboard-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.keyboard-btn.correct {
    background-color: #10b981;
    color: white;
}

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

#game-container {
    transition: all 0.5s ease;
}

#start-btn {
    box-shadow: 0 4px 6px -1px rgba(59, 130, 246, 0.4);
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.7;
    }
}

.pulsing {
    animation: pulse 1.5s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}

@media (max-width: 480px) {
    .letter-tile {
        width: 36px;
        height: 36px;
        font-size: 18px;
    }
    .keyboard-btn {
        font-size: 14px;
        padding: 8px 0;
    }
}