/* Lesson overlay: tabs, teaching notes, quiz. */
/* ── Lesson overlay ── */
.lesson { position: fixed; inset: 0; z-index: 70; background: var(--paper); overflow-y: auto; overscroll-behavior: contain; }
.lesson-head { position: sticky; top: 0; z-index: 2; background: var(--rail); color: #fff;
  padding: calc(env(safe-area-inset-top, 0px) + 12px) max(16px, env(safe-area-inset-right, 0px)) 0 max(16px, env(safe-area-inset-left, 0px)); }
.lesson-head .row { max-width: 860px; margin: 0 auto; display: flex; gap: 12px; align-items: flex-start; }
.lesson-head h2 { font-family: var(--f-display); font-size: 1.5rem; letter-spacing: .02em; line-height: 1.1; }
.lesson-head .k { color: var(--brass); font-size: .72rem; letter-spacing: .1em; text-transform: uppercase; font-weight: 600; }
.lesson-head .x { margin-left: auto; background: rgba(255,255,255,.1); border: 0; color: #fff; border-radius: 6px; padding: 6px 12px; font-weight: 600; flex-shrink: 0; }
.ltabs { max-width: 860px; margin: 10px auto 0; display: flex; gap: 4px; }
.ltabs button { background: none; border: 0; color: var(--rail-ink); padding: 8px 14px; font-weight: 600; border-bottom: 3px solid transparent; }
.ltabs button.on { color: #fff; border-bottom-color: var(--brass); }
.lesson-body { max-width: 860px; margin: 0 auto; padding-block: 20px 60px; padding-left: max(16px, env(safe-area-inset-left, 0px)); padding-right: max(16px, env(safe-area-inset-right, 0px)); display: flex; flex-direction: column; gap: 16px; }
.secnav { display: flex; gap: 6px; overflow-x: auto; padding-bottom: 2px; }
.secnav button { flex-shrink: 0; border: 1px solid var(--line); background: var(--surface); border-radius: 99px; padding: 5px 12px; font-size: .8rem; font-weight: 600; color: var(--ink-2); }
.secnav button.on { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.sec { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 20px; display: flex; flex-direction: column; gap: 14px; min-width: 0; }
.sec h3 { font-family: var(--f-display); font-size: 1.45rem; letter-spacing: .02em; }
.sec h4 { font-size: .8rem; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-3); margin-top: 4px; }
.sec .lead { font-size: 1rem; max-width: 65ch; }
.sec .para { color: var(--ink-2); max-width: 65ch; font-size: .93rem; }
.quote { font-family: var(--f-display); font-size: 1.35rem; letter-spacing: .01em; border-left: 4px solid var(--brass); padding: 2px 0 2px 14px; }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(210px, 1fr)); gap: 10px; }
.card { border: 1px solid var(--line); border-radius: 6px; padding: 12px; background: var(--sunk); }
.card .n { font-family: var(--f-mono); font-size: .75rem; color: var(--brass); }
.card b { display: block; font-size: .92rem; margin: 2px 0 3px; }
.card p { font-size: .84rem; color: var(--ink-2); }
.card.hl { border-color: var(--brass); background: var(--brass-soft); }
.steps { display: flex; flex-direction: column; counter-reset: s; }
.step { display: grid; grid-template-columns: 34px minmax(0, 1fr); gap: 12px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.step:last-child { border-bottom: 0; }
.step .n { width: 30px; height: 30px; border-radius: 50%; border: 2px solid var(--ink); display: grid; place-items: center; font-family: var(--f-mono); font-size: .82rem; }
.step.hl .n { background: var(--brass); border-color: var(--brass); color: var(--brass-ink); }
.step b { display: block; font-size: .95rem; }
.step p { font-size: .86rem; color: var(--ink-2); }
.acro { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 8px; }
.acro div { border: 1px solid var(--line); border-radius: 6px; padding: 10px; background: var(--sunk); }
.acro div.hl { border-color: var(--brass); background: var(--brass-soft); }
.acro .L { font-family: var(--f-display); font-size: 1.8rem; line-height: 1; color: var(--brass); }
.acro b { display: block; font-size: .88rem; }
.acro p { font-size: .78rem; color: var(--ink-2); }
.note { border-radius: 6px; padding: 12px 14px; font-size: .88rem; border: 1px solid var(--line); background: var(--sunk); border-left: 4px solid var(--p2); }
.note.warn { border-left-color: var(--bad); }
.note b { display: block; font-size: .74rem; letter-spacing: .08em; text-transform: uppercase; margin-bottom: 3px; color: var(--ink-2); }
.flow { display: flex; flex-wrap: wrap; gap: 6px; align-items: stretch; }
.flow div { flex: 1 1 120px; border: 1px solid var(--line); border-radius: 6px; padding: 10px; background: var(--sunk); }
.flow b { display: block; font-family: var(--f-display); font-size: 1.05rem; letter-spacing: .04em; }
.flow span { font-size: .78rem; color: var(--ink-2); }
.split { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
@media (max-width: 560px) { .split { grid-template-columns: 1fr; } .stats { grid-template-columns: 1fr 1fr 1fr; } }
.sec .tbl-wrap td { white-space: normal; }
.pager { display: flex; justify-content: space-between; gap: 10px; }

.q { background: var(--surface); border: 1px solid var(--line); border-radius: var(--r); padding: 16px; display: flex; flex-direction: column; gap: 10px; }
.q .qt { font-weight: 600; }
.q .qt span { font-family: var(--f-mono); color: var(--brass); margin-right: 6px; }
.opt { display: flex; gap: 10px; align-items: flex-start; border: 1px solid var(--line); border-radius: 6px; padding: 9px 12px; background: var(--sunk); cursor: pointer; font-size: .92rem; text-align: left; width: 100%; }
.opt .dot { width: 16px; height: 16px; border-radius: 50%; border: 2px solid var(--ink-3); flex-shrink: 0; margin-top: 3px; }
.opt.sel { border-color: var(--ink); }
.opt.sel .dot { border-color: var(--ink); background: var(--ink); box-shadow: inset 0 0 0 3px var(--sunk); }
.opt.right { border-color: var(--ok); background: var(--ok-soft); }
.opt.right .dot { border-color: var(--ok); background: var(--ok); }
.opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.opt.wrong .dot { border-color: var(--bad); background: var(--bad); }
.opt[disabled] { cursor: default; }
.result { border-radius: var(--r); padding: 16px; display: flex; gap: 16px; align-items: center; flex-wrap: wrap; border: 1px solid var(--line); }
.result.pass { background: var(--ok-soft); border-color: var(--ok); }
.result.fail { background: var(--bad-soft); border-color: var(--bad); }
.result .big { font-family: var(--f-display); font-size: 2.4rem; line-height: 1; }