/* Chengyu 0.17: original workspace and learning surfaces; no external fonts or frameworks. */
.platform-hero{position:relative;isolation:isolate;overflow:hidden;padding:clamp(26px,5vw,62px);display:flex;align-items:center;justify-content:space-between;gap:24px;margin-bottom:24px;background:linear-gradient(118deg,var(--surface),var(--accent-soft));min-width:0}
.platform-hero-copy{max-width:720px;position:relative;z-index:1;min-width:0}.platform-hero h1{font-size:clamp(1.9rem,3.5vw,3.4rem);line-height:1.13;letter-spacing:-.045em;margin:15px 0 20px;overflow-wrap:anywhere}.platform-hero p{font-size:1.02rem;color:var(--muted);line-height:1.8;max-width:62ch;margin:0 0 20px}.platform-orbit{width:180px;height:180px;border:1px solid var(--line);border-radius:50%;display:grid;place-items:center;flex:0 0 auto;position:relative;transform:rotate(-14deg)}.platform-orbit:before,.platform-orbit:after{content:"";position:absolute;inset:18px;border:1px solid var(--line);border-radius:36%;transform:rotate(45deg)}.platform-orbit:after{inset:-28px;border-style:dashed;opacity:.6;transform:rotate(-15deg)}.platform-orbit>span{display:grid;place-items:center;width:86px;height:86px;border:1px solid var(--line);border-radius:28px;background:var(--surface);box-shadow:0 18px 40px -25px var(--accent)}.platform-orbit .icon{width:40px;height:40px;color:var(--accent)}
.platform-grid{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);gap:24px;align-items:start}.platform-grid>*{min-width:0}.platform-stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(160px,1fr));gap:16px;margin-bottom:24px}.platform-stat{padding:24px;display:flex;flex-direction:column;gap:12px;min-width:0}.platform-stat span{font-size:.83rem;color:var(--muted);overflow-wrap:anywhere}.platform-stat strong{font-size:2.1rem;font-variant-numeric:tabular-nums;font-weight:640;letter-spacing:-.04em}.platform-list-link{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:18px 4px;border-bottom:1px solid var(--line);overflow-wrap:anywhere}.platform-list-link>span{min-width:0}.platform-list-link small{display:block;color:var(--muted);font-size:.78rem;margin-top:5px}.platform-list-link.active{color:var(--accent);border-color:var(--accent)}.platform-output{display:block;min-height:1.6em;margin-top:18px;color:var(--muted);overflow-wrap:anywhere}.platform-code{padding:18px;border-radius:14px;background:var(--accent-soft);font:12px/1.8 ui-monospace,monospace;white-space:pre-wrap;word-break:break-all}.platform-breadcrumb{display:flex;align-items:center;flex-wrap:wrap;gap:12px;font-size:.86rem;color:var(--muted);padding:16px 0}.platform-breadcrumb a{overflow-wrap:anywhere}
.course-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:24px}.course-card{position:relative;min-width:0;overflow:hidden;transition:transform var(--duration) var(--curve),box-shadow var(--duration) var(--curve)}.course-cover{position:relative;aspect-ratio:16/9;background:linear-gradient(140deg,var(--accent-soft),var(--surface));display:grid;place-items:center;overflow:hidden;border-bottom:1px solid var(--line)}.course-cover>img{width:100%;height:100%;object-fit:cover;position:absolute;inset:0;transition:transform 650ms var(--curve)}.course-cover>span:not(.course-index){display:grid;place-items:center;border:1px solid var(--line);border-radius:24px;width:80px;height:80px;transform:rotate(-8deg);background:var(--surface)}.course-cover .icon{width:36px;height:36px;color:var(--accent)}.course-index{position:absolute;right:18px;bottom:14px;font:11px ui-monospace,monospace;letter-spacing:.1em;padding:6px 10px;background:var(--surface);border-radius:20px;border:1px solid var(--line)}.course-card-body{padding:26px;min-width:0}.course-card h2{font-size:1.25rem;line-height:1.5;margin:12px 0}.course-card p{color:var(--muted);font-size:.88rem;line-height:1.75;min-height:3.5em}.course-card .row{border-top:1px solid var(--line);padding-top:18px;margin-top:22px;font-size:.8rem;flex-wrap:wrap;gap:12px}.course-card h2,.course-card p{overflow-wrap:anywhere}
.lesson-outline{list-style:none;padding:0;margin:0;counter-reset:lesson}.lesson-outline li+li{border-top:1px solid var(--line)}.lesson-outline a{display:flex;align-items:center;gap:16px;padding:18px 8px;min-width:0;border-radius:12px;transition:background var(--duration) var(--curve),transform var(--duration) var(--curve)}.lesson-outline .grow{min-width:0}.lesson-outline a.active{background:var(--accent-soft);color:var(--accent)}.lesson-outline strong{font-size:.92rem;line-height:1.6;overflow-wrap:anywhere;flex:1;min-width:0}.lesson-outline small{display:block;margin-top:6px;color:var(--muted);font-size:.76rem}.lesson-outline [aria-disabled=true]{opacity:.72}.lesson-step{font:13px ui-monospace,monospace;color:var(--muted);flex:0 0 30px}.learning-shell{display:grid;grid-template-columns:minmax(0,1fr) 310px;gap:26px;align-items:start}.learning-main{min-width:0}.learning-heading{padding:8px 0 26px}.learning-heading h1{font-size:clamp(1.6rem,3vw,2.5rem);line-height:1.3;overflow-wrap:anywhere;margin:12px 0 0}.learning-outline{position:sticky;top:100px;max-height:calc(100vh - 130px);overflow:auto}.lesson-player{overflow:hidden;background:#10121a}.lesson-player video{width:100%;max-height:650px;display:block;aspect-ratio:16/9}.lesson-player audio{display:block;width:100%;padding:20px;min-height:88px}.learning-progress-form textarea{min-height:150px}.learning-progress-form[aria-busy=true]{opacity:.8}
.tracking-timeline{padding:0;list-style:none;margin:30px 0;position:relative}.tracking-timeline li{display:grid;grid-template-columns:150px minmax(0,1fr);gap:28px;position:relative;padding:0 0 28px 20px;border-left:1px solid var(--line)}.tracking-timeline li:before{content:"";position:absolute;left:-5px;top:4px;width:9px;height:9px;background:var(--accent);border-radius:50%;box-shadow:0 0 0 5px var(--surface)}.tracking-timeline li:last-child{border-color:transparent;padding-bottom:0}.tracking-timeline time{font-size:.78rem;color:var(--muted);font-variant-numeric:tabular-nums}.tracking-timeline p{margin:8px 0 0;overflow-wrap:anywhere}.support-thread{display:grid;gap:20px;margin:30px 0}.support-message{max-width:90%;padding:22px;border:1px solid var(--line);border-radius:20px 20px 20px 5px;background:var(--surface);min-width:0}.support-message.staff{margin-left:auto;border-radius:20px 20px 5px 20px;background:var(--accent-soft)}.support-message header{display:flex;justify-content:space-between;flex-wrap:wrap;gap:8px;margin-bottom:14px;font-size:.82rem}.support-message time{color:var(--muted);font-size:.74rem}.support-message .prose{font-size:.93rem;overflow-wrap:anywhere}.support-message .prose>:last-child{margin-bottom:0}
@media(hover:hover) and (pointer:fine) and (prefers-reduced-motion:no-preference){html[data-motion="1"] .course-card:hover{transform:translateY(-5px);box-shadow:0 20px 40px -28px var(--accent)}html[data-motion="1"] .course-card:hover .course-cover img{transform:scale(1.035)}html[data-motion="1"] .lesson-outline a[href]:hover{transform:translateX(3px);background:var(--accent-soft)}html[data-motion="1"] .platform-list-link:hover{color:var(--accent)}html[data-motion="1"] .platform-hero .platform-orbit{transition:transform 800ms var(--curve)}html[data-motion="1"] .platform-hero:hover .platform-orbit{transform:rotate(3deg)}}
@media(max-width:1100px){.course-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.learning-shell{grid-template-columns:minmax(0,1fr) 270px}.platform-orbit{width:130px;height:130px}.platform-orbit>span{width:70px;height:70px}.platform-grid{gap:18px}}
@media(max-width:800px){.platform-grid,.learning-shell{grid-template-columns:minmax(0,1fr)}.learning-outline{position:static;max-height:none}.platform-hero{gap:10px}.platform-orbit{position:absolute;right:-85px;bottom:-40px;width:170px;height:170px;opacity:.32;z-index:-1}.platform-hero-copy{max-width:none}.platform-stats{grid-template-columns:repeat(2,minmax(0,1fr))}.tracking-timeline li{grid-template-columns:minmax(0,1fr);gap:8px}.support-message{max-width:100%}}
@media(max-width:540px){.course-grid{grid-template-columns:minmax(0,1fr)}.course-card-body{padding:22px}.platform-hero{padding:26px 22px}.platform-stat{padding:20px}.platform-stat strong{font-size:1.7rem}.platform-hero h1{font-size:1.95rem}.lesson-outline a{gap:10px;padding:16px 0}.search-form{flex-wrap:wrap}.search-form>input{flex:1 1 100%}.search-form>select{flex:1 1 auto;width:auto;max-width:75%}.platform-list-link{align-items:flex-start}}
@media(prefers-reduced-motion:reduce){.course-card,.course-cover>img,.lesson-outline a,.platform-orbit{transition:none!important;transform:none!important}}
@media print{.platform-orbit,.platform-job,.learning-progress-form{display:none!important}.platform-grid,.learning-shell{display:block}.learning-outline{position:static}.platform-hero{background:none;box-shadow:none}}