/* Lớp Chuyên Sâu — design system ocean-blue sáng (của chúng ta, tham khảo SamEducation) */
:root{
  --paper:#EDF1F5; --paper-2:#E0E7EE; --card:#FBFCFD;
  --ink:#0D1F33; --ink-2:#18304A; --ink-soft:#3A4C60; --muted:#6F8090;
  --line:rgba(13,31,51,.14); --line-soft:rgba(13,31,51,.07);
  --accent:#1C6FB8; --accent-2:#0E4C84; --gold:#C99A4E;
  --green:#1F9D63; --on-dark:#F3EEE4;
  --maxw:1280px; --gutter:clamp(18px,5vw,72px); --radius:10px; --header-h:68px;
}
*{box-sizing:border-box}
body{margin:0;background:var(--paper);color:var(--ink);
  font-family:"Be Vietnam Pro",system-ui,sans-serif;font-size:16px;line-height:1.6;-webkit-font-smoothing:antialiased}
a{color:inherit;text-decoration:none}
h1,h2,h3{font-family:"Playfair Display",serif;font-weight:600;line-height:1.12;margin:0}
.h1{font-size:clamp(34px,5vw,60px)} .h2{font-size:clamp(26px,3.4vw,40px)} .h3{font-size:clamp(19px,2vw,24px)}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 var(--gutter)}
.wrap-wide{max-width:1440px;margin:0 auto;padding:0 var(--gutter)}
.page{min-height:100vh;padding-top:var(--header-h)}
.tiny{font-size:13px} .small{font-size:14.5px} .muted{color:var(--muted)}
.lead{font-size:clamp(17px,1.6vw,20px);color:var(--ink-soft)}
.label{font-size:12px;font-weight:600;letter-spacing:.18em;text-transform:uppercase;color:var(--accent)}
.measure{max-width:62ch}

/* buttons */
.btn{display:inline-flex;align-items:center;gap:8px;padding:12px 18px;border:1px solid var(--line);
  border-radius:8px;background:var(--card);font:inherit;font-weight:600;font-size:14.5px;cursor:pointer;
  transition:.25s cubic-bezier(.16,1,.3,1)}
.btn:hover{transform:translateY(-1px);box-shadow:0 6px 18px rgba(13,31,51,.08)}
.btn-accent{background:var(--accent);border-color:var(--accent);color:#fff}
.btn-accent:hover{background:var(--accent-2)}
.btn-outline{background:transparent;border-color:var(--accent);color:var(--accent)}
.btn-gold{background:var(--gold);border-color:var(--gold);color:#1c130a}
.btn[disabled]{opacity:.45;cursor:not-allowed;transform:none;box-shadow:none}

/* header */
.hdr{position:fixed;top:0;left:0;right:0;height:var(--header-h);z-index:50;
  background:rgba(237,241,245,.82);backdrop-filter:blur(10px);border-bottom:1px solid var(--line-soft)}
.hdr .wrap-wide{height:100%;display:flex;align-items:center;justify-content:space-between;gap:16px}
.brand{font-family:"Playfair Display",serif;font-weight:700;font-size:20px;color:var(--ink)}
.brand b{color:var(--accent)}
.nav{display:flex;align-items:center;gap:10px}

/* cards / badges */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px}
.badge{display:inline-flex;align-items:center;gap:6px;padding:5px 12px;border-radius:100px;
  font-size:12.5px;font-weight:600;background:rgba(28,111,184,.1);color:var(--accent)}
.badge-gold{background:rgba(201,154,78,.14);color:#9a7128}
.badge-green{background:rgba(31,157,99,.12);color:var(--green)}
.progress{height:6px;background:var(--paper-2);border-radius:100px;overflow:hidden}
.progress>i{display:block;height:100%;background:var(--accent);border-radius:100px;transition:width .5s}

/* hero */
.hero{padding:clamp(40px,7vw,90px) 0 clamp(30px,5vw,60px)}
.hero h1{max-width:16ch}
.pill-price{display:inline-flex;flex-direction:column;gap:2px;padding:14px 22px;border-radius:12px;
  background:var(--ink);color:var(--on-dark)}
.pill-price b{font-family:"Playfair Display";font-size:30px;color:#fff}
.grid{display:grid;gap:20px}
.g3{grid-template-columns:repeat(3,1fr)} .g2{grid-template-columns:repeat(2,1fr)}

/* learn layout */
.learn-grid{display:grid;grid-template-columns:1fr 380px;gap:34px}
.player{position:relative;aspect-ratio:16/9;border-radius:12px;overflow:hidden;
  display:grid;place-items:center;background:linear-gradient(135deg,#16304a,#0b1c30)}
.player .ph-tag{position:absolute;left:14px;top:12px;font-size:12px;font-weight:700;color:#fff;
  background:rgba(0,0,0,.4);padding:4px 10px;border-radius:6px;z-index:3}
.player .ph-mid{color:rgba(255,255,255,.85);text-align:center;z-index:2}
.player .ph-mid .big{width:78px;height:78px;border-radius:50%;background:rgba(255,255,255,.14);
  border:1px solid rgba(255,255,255,.4);display:grid;place-items:center;margin:0 auto 12px}
.tabbar{display:flex;gap:4px;border-bottom:1px solid var(--line);margin-top:26px}
.tabbar button{background:none;border:none;padding:12px 18px;font:inherit;font-weight:600;font-size:14.5px;
  color:var(--muted);border-bottom:2px solid transparent;margin-bottom:-1px;cursor:pointer}
.tabbar button.on{color:var(--ink);border-bottom-color:var(--accent)}

/* sidebar curriculum */
.side{position:sticky;top:calc(var(--header-h) + 14px);border:1px solid var(--line);border-radius:12px;
  overflow:hidden;background:var(--card)}
.side .head{padding:16px 18px;border-bottom:1px solid var(--line)}
.side .body{max-height:min(72vh,760px);overflow-y:auto}
.ch-head{width:100%;background:none;border:none;padding:14px 18px;display:flex;gap:10px;align-items:center;
  text-align:left;font:inherit;cursor:pointer;border-top:1px solid var(--line-soft)}
.ch-head .num{font-weight:700;color:var(--accent)}
.les{display:flex;gap:12px;align-items:center;padding:11px 16px;cursor:pointer;border-top:1px solid var(--line-soft)}
.les:hover{background:var(--paper)}
.les.on{background:#e9f1f9;box-shadow:inset 3px 0 0 var(--accent)}
.les .thumb{position:relative;width:78px;height:48px;border-radius:6px;flex:0 0 auto;
  background:linear-gradient(135deg,#1d3a57,#0d2236);display:grid;place-items:center;color:#fff;font-size:12px;font-weight:700}
.les .thumb .lock{opacity:.85}
.les .thumb .done{position:absolute;inset:0;background:rgba(31,157,99,.85);display:grid;place-items:center;border-radius:6px}
.les.locked{opacity:.62;cursor:not-allowed}

/* exercise panel (BÀI TẬP) */
.exbox{border:1px solid var(--line);border-radius:12px;overflow:hidden;background:var(--card)}
.exbox .top{padding:16px 20px;background:#0d1f33;color:var(--on-dark);display:flex;justify-content:space-between;align-items:center;gap:12px}
.exbox .urlrow{display:flex;gap:8px;padding:16px 20px;border-bottom:1px solid var(--line);align-items:center}
.exbox .url{flex:1;font-family:ui-monospace,monospace;font-size:13.5px;background:var(--paper);padding:11px 14px;
  border-radius:8px;border:1px solid var(--line);overflow-x:auto;white-space:nowrap}
.exbox .steps{padding:18px 20px}
.exbox .steps ol{margin:0;padding-left:20px;display:grid;gap:8px;color:var(--ink-soft)}

@media(max-width:980px){ .learn-grid{grid-template-columns:1fr} .g3{grid-template-columns:1fr} .g2{grid-template-columns:1fr} }
.center{text-align:center}
.row{display:flex;gap:12px;align-items:center;flex-wrap:wrap}
.spread{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap}
.mt{margin-top:clamp(20px,4vw,44px)}
.modal-bg{position:fixed;inset:0;background:rgba(13,31,51,.55);z-index:100;display:grid;place-items:center;padding:20px}
.modal{background:var(--card);border-radius:16px;max-width:520px;width:100%;padding:28px;max-height:90vh;overflow:auto}

/* nội dung HTML bài học */
.lesson h3{font-family:"Be Vietnam Pro";font-size:18px;font-weight:700;color:var(--ink);margin:22px 0 8px}
.lesson p{margin:8px 0;color:var(--ink-soft)}
.lesson .goal{font-size:16px;color:var(--ink);font-weight:500;margin:6px 0 4px}
.lesson .steps{padding-left:20px;display:grid;gap:8px;margin:8px 0;color:var(--ink-soft)}
.lesson .tipbox{background:#eef6ee;border:1px solid #cfe6d4;border-radius:10px;padding:14px 18px;margin:16px 0}
.lesson .tipbox ul{margin:8px 0 0;padding-left:18px;color:#2a5c3e}
.lesson .note{background:rgba(201,154,78,.1);border-radius:8px;padding:10px 14px;color:#8a6420}
.lesson .vidnote{margin-top:18px;padding:12px 16px;border:1px dashed var(--line);border-radius:8px;color:var(--muted);font-size:14px}

/* gallery ảnh hướng dẫn từng bước */
.guide-imgs{display:grid;gap:14px;margin:12px 0}
.guide-imgs img{width:100%;border:1px solid var(--line);border-radius:10px;box-shadow:0 4px 14px rgba(13,31,51,.08)}

/* trợ lý hỏi-đáp */
.asst-fab{position:fixed;right:20px;bottom:20px;z-index:200;background:var(--accent);color:#fff;border:none;
  padding:12px 18px;border-radius:100px;font:inherit;font-weight:600;cursor:pointer;box-shadow:0 8px 24px rgba(28,111,184,.35)}
.asst-panel{position:fixed;right:20px;bottom:74px;z-index:200;width:min(380px,92vw);height:min(520px,70vh);
  background:var(--card);border:1px solid var(--line);border-radius:16px;display:flex;flex-direction:column;
  overflow:hidden;box-shadow:0 16px 48px rgba(13,31,51,.22)}
.asst-head{padding:14px 16px;background:#0d1f33;color:var(--on-dark);font-weight:600;font-size:14.5px}
.asst-body{flex:1;overflow-y:auto;padding:12px;display:flex;flex-direction:column;gap:8px}
.asst-msg{padding:10px 13px;border-radius:12px;font-size:14px;max-width:88%;line-height:1.5;white-space:pre-wrap}
.asst-msg.u{align-self:flex-end;background:var(--accent);color:#fff}
.asst-msg.a{align-self:flex-start;background:var(--paper);color:var(--ink);border:1px solid var(--line)}
.asst-input{display:flex;gap:8px;padding:10px;border-top:1px solid var(--line)}
.asst-input input{flex:1;padding:10px 12px;border:1px solid var(--line);border-radius:8px;font:inherit}

/* bài tập: ô nộp + chấm điểm */
.ex-work{width:100%;margin-top:12px;padding:11px 13px;border:1px solid var(--line);border-radius:9px;
  font:inherit;font-size:14px;resize:vertical;box-sizing:border-box}
.grade-box{margin-top:12px;padding:11px 14px;border-radius:9px;font-size:14px;line-height:1.5}
.grade-box.ok{background:#e7f6ec;border:1px solid #b6e0c4;color:#1c6b3a}
.grade-box.no{background:#fdf0e7;border:1px solid #f0cdb0;color:#9a5320}

/* login tại chỗ */
.lg-inp{width:100%;margin-top:10px;padding:12px 14px;border:1px solid var(--line);border-radius:9px;
  font:inherit;font-size:15px;box-sizing:border-box}
.lg-inp:focus{outline:none;border-color:var(--accent)}
.lg-err{margin-top:10px;padding:9px 12px;background:#fdf0e7;border:1px solid #f0cdb0;color:#9a5320;
  border-radius:8px;font-size:13.5px}
.lg-or{text-align:center;color:var(--muted);font-size:12.5px;margin:14px 0 10px;position:relative}

/* gallery ảnh hướng dẫn có chú thích bước */
.guide-imgs .gi-fig{margin:0}
.guide-imgs figcaption{font-size:13px;color:var(--ink-soft);margin-top:6px;font-weight:500;line-height:1.4}

/* hộp link tài nguyên (vd scenario Make) */
.link-box{margin:16px 0;padding:14px 16px;background:#eef6ff;border:1px solid #c3ddf5;border-radius:12px}
.link-row{display:flex;justify-content:space-between;align-items:center;gap:10px;margin-top:10px;flex-wrap:wrap}
.link-row a{background:var(--accent);color:#fff;padding:8px 14px;border-radius:8px;text-decoration:none;font-weight:600;font-size:14px;white-space:nowrap}

/* nút đăng nhập Google */
.btn-google{width:100%;margin-top:4px;display:flex;align-items:center;justify-content:center;gap:10px;
  padding:11px 14px;border:1px solid var(--line);border-radius:9px;background:#fff;font:inherit;font-size:14.5px;
  font-weight:600;color:var(--ink);cursor:pointer}
.btn-google:hover{background:var(--paper)}

/* học tương tác: flash card + trắc nghiệm */
.qz-block{margin-top:18px}
.qz-h{font-weight:700;font-size:15px;margin-bottom:12px;display:flex;align-items:center;gap:10px}
.qz-cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(220px,1fr));gap:12px}
.flash{perspective:1000px;cursor:pointer;height:130px}
.flash-in{position:relative;width:100%;height:100%;transition:transform .55s cubic-bezier(.16,1,.3,1);transform-style:preserve-3d}
.flash.on .flash-in{transform:rotateY(180deg)}
.flash-face{position:absolute;inset:0;backface-visibility:hidden;border:1px solid var(--line);border-radius:12px;
  padding:16px;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;gap:8px}
.flash-face.front{background:var(--card);font-weight:600;font-size:15px}
.flash-face.back{background:var(--accent);color:#fff;transform:rotateY(180deg);font-size:14px;line-height:1.5}
.flash-hint{font-size:11px;color:var(--muted);font-weight:400}
.qz-score{font-size:13px;padding:3px 10px;border-radius:100px}
.qz-score.ok{background:rgba(31,157,99,.14);color:var(--green)} .qz-score.no{background:#fdf0e7;color:#9a5320}
.qz-q{margin-bottom:18px}
.qz-qt{font-weight:600;margin-bottom:8px}
.qz-opt{display:flex;align-items:center;gap:10px;padding:10px 14px;border:1px solid var(--line);border-radius:9px;
  margin-top:7px;cursor:pointer;font-size:14.5px;transition:.2s}
.qz-opt:hover{border-color:var(--accent)}
.qz-opt.sel{border-color:var(--accent);background:rgba(28,111,184,.07)}
.qz-opt.correct{border-color:var(--green);background:rgba(31,157,99,.1)}
.qz-opt.wrong{border-color:#e0a890;background:#fdf0e7}
.qz-radio{width:18px;height:18px;border-radius:50%;border:1.5px solid var(--accent);display:inline-flex;
  align-items:center;justify-content:center;color:var(--accent);font-size:11px;flex:0 0 auto}
.qz-explain{margin-top:8px;font-size:13.5px;padding:8px 12px;border-radius:8px}
.qz-explain.ok{background:rgba(31,157,99,.1);color:#1c6b3a} .qz-explain.no{background:#fdf0e7;color:#9a5320}
.qz-hint{margin-top:8px;font-size:13.5px;padding:8px 12px;border-radius:8px;background:rgba(201,154,78,.12);color:#9a7128;font-weight:500}