.national-light .proof-demo { width: 100%; max-width: 420px; justify-self: center; }
.proof-demo video { box-sizing: border-box; object-fit: contain; }
.proof-chapters { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); margin-top: 24px; border-top: 1px solid #ffffff40; }
.proof-chapters[hidden] { display: none; }
.proof-chapters button { min-height: 64px; padding: 12px 6px; border: 0; border-bottom: 2px solid transparent; background: transparent; color: #bbb; font: 400 13px/1.5 Inter, Arial, sans-serif; letter-spacing: 0; cursor: pointer; }
.proof-chapters button small { display: block; margin-bottom: 4px; font-size: 11px; font-variant-numeric: tabular-nums; }
.proof-chapters button[aria-pressed="true"] { color: #fff; border-bottom-color: #fff; }
.proof-chapters button:hover { color: #fff; background: #ffffff08; }
.proof-chapters button:focus-visible { outline: 2px solid #fff; outline-offset: 3px; }
.proof-demo .proof-status { min-height: 0; margin: 0; color: #ddd; font: 400 13px/1.6 Inter, Arial, sans-serif; letter-spacing: 0; }
.proof-demo .proof-status:not(:empty) { margin-top: 12px; }
@media (max-width: 767px) { .national-light .proof-demo { max-width: 390px; } }