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);
}

/* ── Rings ── */
.scene {
    position: relative;
    width: 400px;
    height: 400px;
    transform-style: preserve-3d;
    perspective: 800px;
}

.ring {
    position: absolute;
    top: 50%;
    left: 50%;
    border-radius: 50%;
    border-style: solid;
    border-color: rgba(255, 255, 255, 0.25);
    background: transparent;
    transform-style: preserve-3d;
}

.ring-1 {
    width: 360px;
    height: 360px;
    margin-top: -180px;
    margin-left: -180px;
    border-width: 1px;
    border-color: rgba(255, 255, 255, 0.15);
    animation: spin-1 16s linear infinite;
}

.ring-2 {
    width: 300px;
    height: 300px;
    margin-top: -150px;
    margin-left: -150px;
    border-width: 1px;
    border-color: rgba(255, 255, 255, 0.2);
    animation: spin-2 12s linear infinite;
}

.ring-3 {
    width: 240px;
    height: 240px;
    margin-top: -120px;
    margin-left: -120px;
    border-width: 1.5px;
    border-color: rgba(255, 255, 255, 0.3);
    animation: spin-3 9s linear infinite;
}

.ring-4 {
    width: 180px;
    height: 180px;
    margin-top: -90px;
    margin-left: -90px;
    border-width: 1.5px;
    border-color: rgba(255, 255, 255, 0.4);
    animation: spin-4 7s linear infinite;
}

.ring-5 {
    width: 120px;
    height: 120px;
    margin-top: -60px;
    margin-left: -60px;
    border-width: 2px;
    border-color: rgba(255, 255, 255, 0.5);
    animation: spin-5 5s linear infinite;
}

.ring-6 {
    width: 60px;
    height: 60px;
    margin-top: -30px;
    margin-left: -30px;
    border-width: 2px;
    border-color: rgba(255, 255, 255, 0.6);
    animation: spin-6 3s linear infinite;
}

@keyframes spin-1 {
    from { transform: rotateX(60deg) rotateY(0deg); }
    to   { transform: rotateX(60deg) rotateY(360deg); }
}

@keyframes spin-2 {
    from { transform: rotateX(-45deg) rotateZ(0deg); }
    to   { transform: rotateX(-45deg) rotateZ(360deg); }
}

@keyframes spin-3 {
    from { transform: rotateY(70deg) rotateX(0deg); }
    to   { transform: rotateY(70deg) rotateX(360deg); }
}

@keyframes spin-4 {
    from { transform: rotateZ(30deg) rotateY(0deg); }
    to   { transform: rotateZ(30deg) rotateY(360deg); }
}

@keyframes spin-5 {
    from { transform: rotateX(-60deg) rotateZ(0deg); }
    to   { transform: rotateX(-60deg) rotateZ(-360deg); }
}

@keyframes spin-6 {
    from { transform: rotateY(-45deg) rotateX(0deg); }
    to   { transform: rotateY(-45deg) rotateX(-360deg); }
}