.letter-tile {
    width: 48px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: bold;
    text-transform: uppercase;
    border-radius: 0.5rem;
    cursor: pointer;
    user-select: none;
    transition: all 0.2s ease;
}

.tile-empty {
    background-color: #1e293b;
    border: 2px dashed #475569;
    color: transparent;
}

.tile-filled {
    background-color: #0f172a;
    border: 2px solid #38bdf8;
    color: #e0f2fe;
    box-shadow: 0 4px 0 #0369a1;
}

.tile-filled:active {
    transform: translateY(4px);
    box-shadow: 0 0 0 #0369a1;
}

.tile-source {
    background-color: #334155;
    border: 2px solid #64748b;
    color: #f8fafc;
    box-shadow: 0 4px 0 #1e293b;
}

.tile-source:active {
    transform: translateY(4px);
    box-shadow: 0 0 0 #1e293b;
}

.tile-source.hidden-tile {
    opacity: 0.2;
    pointer-events: none;
}

.success-glow {
    animation: glow 1s ease-out;
}

@keyframes glow {
    0% { box-shadow: 0 0 0px #38bdf8; }
    50% { box-shadow: 0 0 20px #38bdf8, inset 0 0 10px #38bdf8; }
    100% { box-shadow: 0 0 0px #38bdf8; }
}