body {
    margin: 0;
    padding: 0;
    min-height: 100vh;
    background-color: black;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
}

/* ── Back Button ── */
.back-btn {
    position: fixed;
    top: 1rem;
    left: 1rem;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 6px;
    background: rgba(255, 255, 255, 0.05);
    opacity: 0.3;
    transition: opacity 0.3s, border-color 0.3s;
}

.back-btn:hover {
    opacity: 1;
    border-color: rgba(255, 255, 255, 0.4);
}

.back-btn img {
    width: 14px;
    height: 14px;
    filter: brightness(0) invert(0.7);
}

/* ── Pulse ── */
.scene {
    position: relative;
    width: 100vmin;
    height: 100vmin;
}

.dot {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 6px;
    height: 6px;
    margin-top: -3px;
    margin-left: -3px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.8);
    box-shadow: 0 0 10px rgba(255, 255, 255, 0.3);
}

.ripple {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    margin-top: -10px;
    margin-left: -10px;
    border-radius: 50%;
    border: 1px solid rgba(255, 255, 255, 0.6);
    background: transparent;
    animation: expand 6s linear infinite;
}

.ripple-1 { animation-delay: 0s; }
.ripple-2 { animation-delay: 1s; }
.ripple-3 { animation-delay: 2s; }
.ripple-4 { animation-delay: 3s; }
.ripple-5 { animation-delay: 4s; }
.ripple-6 { animation-delay: 5s; }

@keyframes expand {
    0% {
        width: 20px;
        height: 20px;
        margin-top: -10px;
        margin-left: -10px;
        opacity: 0.7;
        border-width: 2px;
    }
    100% {
        width: 90vmin;
        height: 90vmin;
        margin-top: -45vmin;
        margin-left: -45vmin;
        opacity: 0;
        border-width: 0.5px;
    }
}