/* ==========================================================================
   CSIP12 Class/Subject chapter pages (Phase 3C) — frozen Phase 2 "ClassSubject" design.
   Built on csip-ui.css tokens (light + dark). Scoped under .csip-hub.
   ========================================================================== */

.csip-hub { background: var(--c-paper); color: var(--c-ink); font-family: var(--f-sans); }
.csip-hub a { text-decoration: none; }
.csip-hub h1, .csip-hub h2 { font-family: var(--f-serif) !important; color: var(--c-ink); margin: 0; letter-spacing: 0; }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }

.csip-hub__layout { display: flex; min-height: 100%; }
.csip-hub__main { flex: 1; min-width: 0; max-width: 1080px; padding: 16px 18px 24px; }
@media (min-width: 768px) { .csip-hub__main { padding: 32px 40px 88px; } }
@media (min-width: 1280px) { .csip-hub__main { padding: 36px 64px 88px; } }

/* ---------- Unit spine (desktop) ---------- */
.csip-spine { display: none; }
@media (min-width: 1024px) {
    .csip-spine {
        display: flex; flex-direction: column; align-items: center; gap: 10px;
        position: sticky; top: 0; align-self: flex-start; height: calc(100vh - var(--bar-h));
        width: 64px; flex-shrink: 0; padding: 22px 0; background: #1B2A41; box-sizing: border-box;
    }
    html.dark .csip-spine { background: #0B1220; border-right: 1px solid var(--c-rule); }
}
.csip-spine__tab {
    writing-mode: vertical-rl; padding: 14px 0; width: 34px; border-radius: 4px; text-align: center;
    color: #B9C2CE; font-size: 11px; font-weight: 700; letter-spacing: 0.05em; text-transform: uppercase;
}
.csip-spine__tab:hover { color: #FFFFFF; background: rgba(255, 255, 255, 0.06); }
.csip-spine__tab.is-active { background: var(--c-teal); color: #FFFFFF; }

/* ---------- Header ---------- */
.csip-crumbs { display: flex; flex-wrap: wrap; gap: 6px; font-size: 11.5px; color: var(--c-ink-3); margin-bottom: 8px; }
.csip-crumbs a { color: var(--c-ink-3); }
.csip-crumbs a:hover { color: var(--c-teal); }
.csip-crumbs [aria-current] { color: var(--c-ink); font-weight: 600; }

.csip-hub__head { display: flex; flex-direction: column; gap: 14px; padding-bottom: 14px; border-bottom: 2px solid var(--c-ink); }
@media (min-width: 900px) { .csip-hub__head { flex-direction: row; align-items: flex-end; justify-content: space-between; gap: 24px; padding-bottom: 16px; } }
.csip-hub__head .csip-eyebrow { font-size: 10.5px; margin-bottom: 4px; }
.csip-hub__title { font-size: 22px !important; font-weight: 600 !important; line-height: 1.2 !important; }
@media (min-width: 768px) { .csip-hub__title { font-size: 28px !important; } }
.csip-hub__title span { color: var(--c-teal); }
html.dark .csip-hub__title span { color: var(--c-teal-text); }

.csip-hub__switch { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 6px; }
@media (min-width: 900px) { .csip-hub__switch { display: flex; gap: 6px; flex-shrink: 0; } }
.csip-hub__switch .csip-chip { height: 32px; padding: 0 8px; font-size: 11px; }
@media (min-width: 900px) { .csip-hub__switch .csip-chip { padding: 0 12px; font-size: 11.5px; } }

.csip-hub__intro { font-size: 13px; line-height: 1.65; color: var(--c-ink-2); margin: 14px 0 0; max-width: 820px; }
.csip-hub__intro strong { color: var(--c-ink); font-weight: 600; }
@media (max-width: 767.98px) { .csip-hub__intro { font-size: 12.5px; } }

.csip-hub__progress { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 16px; margin: 18px 0 6px; font-size: 12.5px; color: var(--c-ink-2); }
.csip-hub__progress strong { color: var(--c-ink); }
.csip-hub__progress .csip-progress { flex: 1 1 160px; max-width: 280px; }
.csip-hub__login { background: none; border: 0; padding: 0; font: inherit; font-weight: 700; color: var(--c-teal); cursor: pointer; }
html.dark .csip-hub__login { color: var(--c-teal-text); }

/* ---------- Units and chapter rows ---------- */
.csip-unit { margin-top: 24px; scroll-margin-top: 16px; }
@media (max-width: 767.98px) { .csip-unit { margin-top: 18px; scroll-margin-top: 80px; } }
.csip-hub h2.csip-unit__title { font-family: var(--f-sans) !important; font-size: 11.5px !important; font-weight: 700 !important; letter-spacing: 0.06em; text-transform: uppercase; color: var(--c-amber-text) !important; margin-bottom: 4px !important; }
.csip-unit__title span { color: var(--c-ink-3); font-weight: 600; letter-spacing: 0.02em; text-transform: none; margin-left: 6px; }

.csip-chapters-list { list-style: none; margin: 0; padding: 0; }
.csip-chrow { position: relative; display: flex; align-items: center; gap: 14px; padding: 12px 2px; border-bottom: 1px solid var(--c-rule); }
@media (min-width: 768px) { .csip-chrow { gap: 20px; padding: 14px 4px; } }
.csip-chrow:hover { background: var(--c-band); }
.csip-chrow__num {
    font-family: var(--f-serif); font-weight: 700; font-size: 19px; color: var(--c-ink); width: 40px; flex-shrink: 0;
    font-variant-numeric: tabular-nums;
}
@media (min-width: 768px) { .csip-chrow__num { font-size: 26px; width: 56px; } }
.csip-chrow.is-done .csip-chrow__num { color: var(--c-teal); }
html.dark .csip-chrow.is-done .csip-chrow__num { color: var(--c-teal-text); }
.csip-chrow__body { flex: 1; min-width: 0; }
.csip-chrow__link { display: block; font-size: 13.5px; font-weight: 600; color: var(--c-ink); line-height: 1.35; }
@media (min-width: 768px) { .csip-chrow__link { font-size: 15px; } }
/* The whole row opens the chapter; the like button sits above this layer. */
.csip-chrow__link::after { content: ''; position: absolute; inset: 0; }
.csip-chrow__link:focus-visible { outline: none; }
.csip-chrow__link:focus-visible::after { outline: 2px solid var(--c-teal); outline-offset: -2px; border-radius: 4px; }
.csip-chrow__desc { display: none; }
@media (min-width: 768px) { .csip-chrow__desc { display: block; margin: 3px 0 0; font-size: 12px; color: var(--c-ink-3); line-height: 1.5; } }

.csip-chrow__side { display: flex; align-items: center; gap: 8px; flex-shrink: 0; }
@media (min-width: 768px) { .csip-chrow__side { gap: 14px; } }
.csip-chrow__cta { font-size: 12px; font-weight: 700; color: var(--c-teal); white-space: nowrap; min-width: 56px; text-align: right; }
html.dark .csip-chrow__cta { color: var(--c-teal-text); }
.csip-chrow__cta--revise { color: var(--c-ink-2); font-weight: 600; }
html.dark .csip-chrow__cta--revise { color: var(--c-ink-2); }
@media (max-width: 767.98px) { .csip-chrow .csip-badge { padding: 0 6px; } }

.csip-like {
    position: relative; z-index: 1; display: inline-flex; align-items: center; gap: 5px;
    background: none; border: 0; padding: 6px; margin: -6px 0; border-radius: 6px; cursor: pointer;
    font: 600 11.5px/1 var(--f-sans); color: var(--c-ink-3);
}
.csip-like:hover { background: var(--c-rust-tint); color: var(--c-rust); }
.csip-like i { font-size: 13px; }
.csip-like i.fas { color: var(--c-rust) !important; }
@media (max-width: 767.98px) { .csip-like .like-count { display: none; } }

/* ---------- Empty state ---------- */
.csip-hub__empty { margin-top: 24px; padding: 28px 20px; text-align: center; }
@media (min-width: 768px) { .csip-hub__empty { padding: 44px 40px; } }
.csip-hub__empty-icon {
    width: 56px; height: 56px; margin: 0 auto 14px; border-radius: 999px; display: flex; align-items: center; justify-content: center;
    background: var(--c-teal-tint); color: var(--c-teal); font-size: 22px;
}
html.dark .csip-hub__empty-icon { color: var(--c-teal-text); }
.csip-hub__empty h2 { font-size: 19px !important; font-weight: 600 !important; margin-bottom: 8px !important; }
.csip-hub__empty p { font-size: 13.5px; line-height: 1.6; color: var(--c-ink-2); max-width: 520px; margin: 0 auto 20px; }
.csip-hub__empty-actions { display: flex; flex-direction: column; gap: 10px; align-items: stretch; max-width: 360px; margin: 0 auto; }
@media (min-width: 768px) { .csip-hub__empty-actions { flex-direction: row; flex-wrap: wrap; justify-content: center; max-width: none; } }
.csip-hub__empty-actions .csip-btn { white-space: normal; height: auto; min-height: 40px; padding-top: 10px; padding-bottom: 10px; }

/* Study-resources card (existing include) keeps its own styling; just give it room. */
.csip-hub__main > section:last-child, .csip-hub__main > div:last-child { margin-top: 32px; }