.metro-step { width: 44px; height: 44px; padding: 0; }
.beat-dot {
    width: 22px; height: 22px; border-radius: 50%;
    background: rgba(128, 128, 128, 0.18);
    border: 1px solid rgba(128, 128, 128, 0.45);
    transition: background 0.05s linear, transform 0.05s linear;
}
.beat-dot.is-first { border-color: #dc3545; border-width: 2px; }
.beat-dot.is-on { background: #0071e3; border-color: #0071e3; transform: scale(1.2); }
.beat-dot.is-first.is-on { background: #dc3545; border-color: #dc3545; }