header nav button {
  border: 0;
  background: transparent;
  color: var(--ink);
  font-size: 12px;
  font-weight: 900;
  cursor: pointer;
}

.chapter-grid { display: grid; gap: 22px; margin-top: 34px; }
.chapter-card { overflow: hidden; border: 1px solid var(--line); border-radius: 30px; background: #fff; }
.chapter-card > header { position: static; height: auto; padding: 25px 28px; border: 0; background: var(--chapter-bg); backdrop-filter: none; }
.chapter-card > header > span { display: grid; place-items: center; width: 78px; height: 78px; border-radius: 23px; background: #fff; font-size: 31px; }
.chapter-card > header > span b { color: var(--chapter-color); font-size: 13px; }
.chapter-card h3 { margin: 0; color: var(--navy); font-size: clamp(24px,3vw,34px); }
.chapter-card header p { margin: 2px 0 0; }
.chapter-card > div { display: grid; grid-template-columns: repeat(5,1fr); gap: 1px; background: var(--line); }
.chapter-card button { display: grid; gap: 5px; min-height: 116px; padding: 17px; border: 0; background: #fff; color: var(--ink); text-align: left; cursor: pointer; }
.chapter-card button small { color: var(--chapter-color); font-weight: 900; }
.chapter-card button b { color: var(--navy); }
.chapter-card button:hover,.chapter-card button:focus-visible { position: relative; z-index: 1; outline: 3px solid var(--chapter-color); outline-offset: -3px; background: var(--chapter-bg); }

.safety-flow { display: grid; grid-template-columns: repeat(4,1fr); gap: 12px; margin-top: 28px; }
.safety-flow span { display: grid; gap: 8px; min-height: 125px; place-items: center; padding: 20px; border-radius: 22px; background: #fff0e8; color: var(--navy); font-weight: 900; text-align: center; }
.safety-flow b { display: grid; width: 38px; height: 38px; place-items: center; border-radius: 50%; background: var(--coral); color: #fff; }

.scene-view { display: grid; grid-template-columns: 290px minmax(0,1fr); min-height: calc(100vh - 70px); }
.lesson-nav { position: sticky; top: 70px; align-self: start; height: calc(100vh - 70px); overflow: auto; padding: 27px 20px; background: #e6f4ef; }
.lesson-nav > button { width: 100%; padding: 12px; border: 1px solid var(--line); border-radius: 14px; background: #fff; color: var(--navy); font-weight: 900; cursor: pointer; }
.lesson-nav > p { color: var(--navy); font-weight: 900; }
.lesson-nav nav { display: grid; gap: 8px; }
.lesson-nav nav button { padding: 14px; border: 2px solid transparent; border-radius: 14px; background: #fff; color: var(--ink); text-align: left; cursor: pointer; }
.lesson-nav nav button.active { border-color: var(--green); box-shadow: inset 5px 0 var(--green); font-weight: 900; }
.lesson { min-width: 0; padding: 55px clamp(22px,5vw,85px) 80px; background: #fffdf9; }
.lesson-head { position: static; display: block; height: auto; padding: 0 0 36px; border: 0; background: none; backdrop-filter: none; }
.lesson-head h1 { margin: 5px 0; color: var(--navy); font-size: clamp(38px,5vw,67px); line-height: 1.25; }
.lesson-head p:last-child { font-size: 19px; }
.lesson-step { display: grid; grid-template-columns: 78px minmax(0,1fr); gap: 28px; margin: 24px 0; padding: 34px; border: 1px solid var(--line); border-radius: 28px; background: #fff; }
.lesson-step > span { display: grid; width: 65px; height: 65px; place-items: center; border-radius: 20px; background: var(--mint); color: var(--navy); font-size: 20px; font-weight: 900; }
.lesson-step small,.chapter-message small { color: var(--green); font-weight: 900; letter-spacing: .12em; }
.lesson-step h2 { margin: 3px 0 17px; color: var(--navy); font-size: clamp(27px,3vw,39px); }
.lesson-step p { font-size: 18px; white-space: pre-line; }
.story { background: #fff5ee; }
.hint { border-color: #edd889; background: #fff9df; }
.action { background: #edf8f4; }
.get-help { background: #f2f4fb; }
.get-help a,.related-link { display: inline-flex; margin-top: 10px; color: var(--green); font-weight: 900; }
.choices { display: grid; gap: 10px; }
.choices button { display: grid; grid-template-columns: 42px 1fr; gap: 12px; align-items: center; padding: 15px; border: 2px solid var(--line); border-radius: 16px; background: #fff; color: var(--ink); text-align: left; cursor: pointer; }
.choices button i { display: grid; width: 36px; height: 36px; place-items: center; border-radius: 50%; background: var(--navy); color: #fff; font-style: normal; font-weight: 900; }
.choices button.selected { border-color: var(--coral); background: #fff1ed; }
.feedback { padding: 14px 16px; border-left: 4px solid #e1b94d; background: #fff7dc; font-size: 15px !important; }
.topic-list { display: flex; gap: 8px; flex-wrap: wrap; }
.topic-list span { padding: 7px 11px; border-radius: 99px; background: var(--mint); font-size: 13px; font-weight: 900; }
.chapter-message { display: grid; gap: 9px; margin: 30px 0; padding: 28px; border-radius: 24px; background: linear-gradient(135deg,var(--mint),#fff0ed); }
.chapter-message strong { color: var(--navy); font-size: 20px; line-height: 1.8; }
.lesson-footer { display: grid; grid-template-columns: 1fr auto 1fr; gap: 15px; align-items: center; margin-top: 35px; }
.lesson-footer button { padding: 13px 20px; border: 0; border-radius: 99px; background: var(--navy); color: #fff; font-weight: 900; cursor: pointer; }
.lesson-footer button:last-child { background: var(--coral); }
.lesson-footer button:disabled { opacity: .35; cursor: default; }
.lesson-footer span { color: var(--navy); font-weight: 900; }

@media(max-width:920px){
  .chapter-card > div { grid-template-columns: repeat(2,1fr); }
  .safety-flow { grid-template-columns: repeat(2,1fr); }
  .scene-view { grid-template-columns: 1fr; }
  .lesson-nav { position: static; height: auto; }
  .lesson-nav nav { grid-template-columns: repeat(2,1fr); }
}
@media(max-width:620px){
  .chapter-card > header { align-items: flex-start; padding: 20px; }
  .chapter-card > header > span { width: 58px; height: 58px; font-size: 23px; }
  .chapter-card > div,.safety-flow,.lesson-nav nav { grid-template-columns: 1fr; }
  .lesson { padding: 32px 13px 60px; }
  .lesson-step { grid-template-columns: 1fr; gap: 10px; padding: 23px 19px; }
  .lesson-step > span { width: 52px; height: 52px; border-radius: 16px; }
  .lesson-footer { grid-template-columns: 1fr 1fr; }
  .lesson-footer span { grid-column: 1/3; grid-row: 1; text-align: center; }
}