body {
    text-align: center;
}

.tile {
    height: 180px;
    width: 180px;
    border-radius: 20%;
    border: 10px solid #212529;
    margin: 1.2rem;
    transition: transform 140ms ease, filter 140ms ease, background-color 140ms ease;
    box-shadow: 0 0.25rem 1rem rgba(0,0,0,0.15);
}

@media (min-width: 576px) {
    .tile { height: 200px; width: 200px; }
}

@media (min-width: 992px) {
    .tile { height: 220px; width: 220px; }
}

.btn-container {
    display: flex;
    justify-content: center;
    gap: 0.5rem;
}

.yellow { background-color: #f1c40f; }
.red { background-color: #e74c3c; }
.purple { background-color: #8e44ad; }
.green { background-color: #2ecc71; }

.flash {
    filter: brightness(170%);
    transform: scale(1.04);
}

.userFlash {
    filter: brightness(130%);
    transform: scale(0.98);
}

/* Smooth background feedback without hard flashes */
body.game-over {
    animation: quickFlash 300ms ease-in-out;
}

@keyframes quickFlash {
    0% { background-color: #fff; }
    20% { background-color: #ffdddd; }
    100% { background-color: #fff; }
}