/* A explicação ocupa o centro; a pergunta só entra depois da lição. */
.lesson-page { max-width: 1100px; margin-inline: auto; }
.lesson-page-head { margin-bottom: 1.7rem; }
.lesson-page-head > button { font-size: .85rem; margin-bottom: .6rem; }
.lesson-page-head h1 { margin: 0 0 .65rem; }
.lesson-page-head > p { color: var(--muted); margin: 0; font-size: .97rem; }
.lesson-layout { display: grid; grid-template-columns: minmax(0, 1fr) 256px; gap: 2rem; align-items: start; }
.lesson-main { min-width: 0; }
.lesson-step-head { margin-bottom: 1rem; }
.lesson-step-head > span { color: var(--muted); font-size: .82rem; }
.lesson-step-head h2 { margin: .3rem 0 0; font-size: 1.35rem; }
#lesson-show-chapters { display: none; }
.lesson-video-frame { position: relative; container-type: inline-size; aspect-ratio: 16 / 9; background: #10161a; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.lesson-video-frame video { display: block; width: 100%; height: 100%; object-fit: contain; }
.lesson-video-frame video::cue { background: #10161aec; color: #f2f4ee; font: 500 clamp(12px, 2.35cqw, 20px)/1.35 "Ubuntu Sans", sans-serif; }
.lesson-video-frame video:fullscreen::cue { font-size: 3vh; }
.lesson-media-loading { position: absolute; top: 1rem; left: 1rem; margin: 0; padding: .3rem .6rem; border-radius: 5px; color: #f2f4ee; background: #10161aec; font-size: .85rem; pointer-events: none; }
.lesson-media-status { display: flex; align-items: center; gap: .7rem 1rem; flex-wrap: wrap; min-height: 48px; margin-top: .5rem; }
.lesson-media-status p { color: var(--muted); font-size: .83rem; margin: 0; }
.lesson-media-status button { font-size: .82rem; }
.lesson-transcript { padding-block: .5rem; color: var(--muted); font-size: .88rem; }
.lesson-transcript summary { cursor: pointer; min-height: 44px; display: flex; align-items: center; gap: .55rem; }
.lesson-transcript summary::before { content: "+"; font-size: 1.15rem; }
.lesson-transcript[open] summary::before { content: "−"; }
.lesson-transcript > div { padding: .5rem 1.1rem 0; border-left: 2px solid var(--line); }
.lesson-transcript h3 { color: var(--text); font-size: 1rem; margin: .75rem 0 .5rem; }
.lesson-transcript p { max-width: 65ch; line-height: 1.75; }
.lesson-transcript pre { margin: .85rem 0; padding: .85rem 1rem; overflow: auto; border: 1px solid var(--line); border-radius: 8px; background: var(--panel); font-size: .86rem; }
.lesson-practice-links > a { color: var(--good); text-decoration: underline; text-underline-offset: .18em; }
.lesson-practice-links { display: grid; justify-items: start; gap: .2rem; border-top: 1px solid var(--line); padding-top: .55rem; margin-top: .65rem; font-size: .85rem; }
.lesson-practice-links > a { padding-block: .55rem; }
.lesson-outline { min-width: 0; padding: 1.05rem; border: 2px solid var(--line); border-radius: 16px; background: var(--panel); }
.lesson-outline h2 { font-size: 1.05rem; margin: 0 0 .4rem; }
.lesson-outline progress { display: block; width: 100%; height: 6px; margin: .75rem 0 1rem; }
.lesson-outline ol { list-style: none; padding: .2rem 0 .85rem; margin: 0; display: grid; gap: .35rem; }
.lesson-outline li { min-width: 0; }
.lesson-outline li button { width: 100%; min-height: 46px; display: grid; grid-template-columns: 25px minmax(0, 1fr); gap: .6rem; align-items: start; padding: .65rem .55rem; border: 1px solid transparent; border-radius: 9px; background: transparent; color: var(--muted); font-size: .82rem; line-height: 1.5; text-align: left; }
.lesson-outline li button:hover { background: var(--panel2); border-color: var(--line); color: var(--text); }
.lesson-outline li button > span:first-child { display: grid; place-items: center; width: 25px; height: 25px; border: 1px solid var(--line); border-radius: 50%; background: var(--bg); color: var(--muted); font-size: .73rem; font-weight: 650; line-height: 1; }
.lesson-outline li button > span:last-child { min-width: 0; padding-top: .15rem; overflow-wrap: anywhere; }
.lesson-outline li.is-complete button > span:first-child { color: var(--good); border-color: color-mix(in srgb, var(--good) 50%, var(--line)); background: color-mix(in srgb, var(--good) 9%, var(--panel)); font-size: .88rem; }
.lesson-outline li.is-current button { color: var(--text); background: color-mix(in srgb, var(--good) 7%, var(--panel2)); border-color: color-mix(in srgb, var(--good) 45%, var(--line)); font-weight: 650; }
.lesson-outline li.is-current button > span:first-child { background: var(--accent); color: var(--ink); border-color: var(--accent); }
.lesson-outline :is(summary, button, a):focus-visible { outline: 2px solid var(--good); outline-offset: 3px; }
.lesson-chapter { border-top: 1px solid var(--line); }
.lesson-chapter summary { display: grid; grid-template-columns: 16px minmax(0, max-content) max-content; justify-content: start; align-items: center; gap: .4rem; cursor: pointer; min-height: 48px; font-size: .84rem; line-height: 1.4; padding: .7rem .15rem; border-radius: 6px; list-style: none; }
.lesson-chapter summary::before { content: "+"; color: var(--muted); font-size: 1rem; text-align: center; }
.lesson-chapter[open] summary::before { content: "−"; }
.lesson-chapter summary span { color: var(--muted); font-size: .75rem; font-variant-numeric: tabular-nums; white-space: nowrap; }
.lesson-chapter summary::marker { content: ""; }
.lesson-chapter summary::-webkit-details-marker { display: none; }
.lesson-outline > .lesson-completed-count { margin: 0; color: var(--muted); font-size: .78rem; line-height: 1.5; }
.lesson-outline > p { margin: 1.1rem 0 .3rem; color: var(--muted); font-size: .78rem; line-height: 1.6; }
.lesson-outline > a { display: inline-flex; align-items: center; min-height: 44px; padding-inline: .15rem; text-decoration: underline; text-underline-offset: .2em; font-size: .85rem; }
.lesson-question { margin-top: 1.25rem; padding: 1.5rem; border: 1px solid var(--line); border-radius: 10px; background: var(--panel); }
.lesson-question-label { color: var(--good); font-size: .83rem; margin: 0 0 .6rem; }
.lesson-question-context { color: var(--muted); font-size: .88rem; line-height: 1.6; margin: 0 0 .65rem; }
.lesson-question h2 { font-size: 1.2rem; margin: 0 0 1.25rem; line-height: 1.45; }
.lesson-question .learning-choices { margin-bottom: 1rem; }
.lesson-question .learning-feedback { min-height: 0; margin: 0 0 1rem; font-size: .9rem; line-height: 1.65; }
.lesson-question .learning-feedback:empty { display: none; }
.lesson-question > button { margin-top: .25rem; }
.lesson-sources { display: flex; flex-wrap: wrap; align-items: center; gap: .7rem 1.5rem; padding-top: 1.5rem; margin-top: 1.5rem; border-top: 1px solid var(--line); font-size: .77rem; color: var(--muted); }
.lesson-sources a { text-decoration: underline; }
.lesson-sources span { flex-basis: 100%; }
.lesson-finish { padding: 2rem; }
.lesson-finish h2 { font-size: 1.6rem; }
.lesson-finish-mark { display: grid; place-items: center; width: 45px; height: 45px; border-radius: 50%; border: 1px solid var(--good); color: var(--good); font-size: 1.5rem; }
.lesson-finish > p { color: var(--muted); max-width: 55ch; }
@media (max-width: 950px) {
  .lesson-layout { grid-template-columns: minmax(0, 1fr); gap: 1.5rem; }
  #lesson-show-chapters { display: inline-flex; margin-inline-start: .65rem; font-size: .83rem; }
  .lesson-outline { padding: 1.1rem; }
  .lesson-outline ol { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .4rem .8rem; }
  .lesson-outline > p { margin-top: 1rem; }
}
@media (max-width: 650px) {
  .lesson-video-frame { aspect-ratio: 4 / 3; }
  .lesson-video-frame video { object-position: center top; }
  .lesson-page-head h1 { font-size: 1.9rem; }
  .lesson-step-head h2 { font-size: 1.18rem; }
  .lesson-question { padding: 1.15rem; }
  .lesson-outline { padding: 1rem; }
  .lesson-outline ol { grid-template-columns: 1fr; }
  .lesson-sources { gap: .65rem 1rem; }
  .lesson-sources span { margin-left: 0; flex-basis: 100%; }
  .lesson-finish { padding: 1.4rem; }
}
@media (prefers-reduced-motion: reduce) {
  .lesson-page { scroll-behavior: auto; }
}