:root{
  --bg:#f5f7ff;
  --card:#ffffff;
  --ink:#172033;
  --muted:#6e7890;
  --line:#e5e9f5;
  --primary:#2563eb;
  --primary2:#06b6d4;
  --warm:#fff7ed;
  --green:#16a34a;
  --yellow:#f59e0b;
  --pink:#ec4899;
  --shadow:0 18px 55px rgba(37,99,235,.12);
  --radius:24px;
}
*{box-sizing:border-box}
body{
  margin:0;
  font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",Tahoma,sans-serif;
  color:var(--ink);
  background:
    radial-gradient(circle at 8% 0%, #dbeafe 0 18%, transparent 34%),
    radial-gradient(circle at 88% 8%, #ccfbf1 0 16%, transparent 32%),
    radial-gradient(circle at 55% 100%, #ffe4e6 0 13%, transparent 28%),
    var(--bg);
}
button,input,select{font:inherit}
button{border:0;cursor:pointer}
.app{display:grid;grid-template-columns:300px 1fr;min-height:100vh}
.sidebar{
  padding:24px;
  background:rgba(255,255,255,.78);
  backdrop-filter:blur(18px);
  border-right:1px solid var(--line);
  position:sticky;
  top:0;
  height:100vh;
}
.logo{display:flex;gap:14px;align-items:center;margin-bottom:28px}
.logo-badge{
  width:62px;height:62px;border-radius:22px;
  display:grid;place-items:center;
  background:linear-gradient(135deg,var(--primary),var(--primary2));
  color:white;font-weight:950;font-size:22px;
  box-shadow:0 14px 32px rgba(37,99,235,.28);
}
.logo h1{margin:0;font-size:22px}
.logo p{margin:4px 0 0;color:var(--muted);font-size:13px}
.nav{display:grid;gap:10px}
.nav-btn{
  padding:14px 16px;
  text-align:left;
  border-radius:16px;
  color:#34405a;
  background:transparent;
}
.nav-btn:hover,.nav-btn.active{background:#eaf2ff;color:var(--primary);font-weight:900}
.student-box{
  margin-top:24px;
  background:#fff;
  border:1px solid var(--line);
  border-radius:22px;
  padding:16px;
  box-shadow:var(--shadow);
}
.student-box label{font-weight:850;font-size:13px;color:#4b5565}
input,select{
  width:100%;
  margin-top:8px;
  padding:13px 14px;
  border-radius:15px;
  border:1px solid var(--line);
  outline:none;
  background:#fff;
}
input:focus,select:focus{border-color:#93c5fd;box-shadow:0 0 0 4px rgba(37,99,235,.1)}
.student-box button{width:100%;margin-top:10px;padding:12px;border-radius:14px;background:#eaf2ff;color:var(--primary);font-weight:950}
.main{padding:28px;max-width:1220px;width:100%;margin:0 auto}
.topbar{display:flex;justify-content:space-between;align-items:center;gap:16px;margin-bottom:24px}
.tag{
  color:var(--primary);
  background:#eaf2ff;
  border-radius:999px;
  padding:6px 10px;
  font-size:12px;
  font-weight:950;
  display:inline-flex;
  width:max-content;
}
.topbar h2{font-size:36px;margin:10px 0 0}
.status-card{
  min-width:210px;
  padding:16px 18px;
  background:rgba(255,255,255,.84);
  border:1px solid var(--line);
  border-radius:22px;
  box-shadow:var(--shadow);
  display:grid;
  gap:4px;
}
.status-card span{color:var(--muted)}
.status-card strong{font-size:22px}
.view{display:none}
.view.active{display:block}
.hero{
  display:grid;
  grid-template-columns:1fr 360px;
  gap:22px;
  padding:30px;
  border-radius:34px;
  background:linear-gradient(135deg,#1d4ed8,#0891b2);
  color:white;
  box-shadow:var(--shadow);
}
.pill{
  display:inline-flex;
  padding:7px 12px;
  background:rgba(255,255,255,.18);
  border:1px solid rgba(255,255,255,.28);
  border-radius:999px;
  font-weight:900;
}
.hero h3{font-size:40px;line-height:1.15;margin:18px 0 12px}
.hero p{font-size:17px;line-height:1.7;margin:0;opacity:.92}
.hero-actions{display:flex;gap:12px;margin-top:22px;flex-wrap:wrap}
.primary,.ghost,.soft-btn{
  padding:13px 18px;
  border-radius:16px;
  font-weight:950;
}
.primary{background:linear-gradient(135deg,var(--primary),var(--primary2));color:white;box-shadow:0 12px 32px rgba(37,99,235,.25)}
.ghost{background:rgba(255,255,255,.18);border:1px solid rgba(255,255,255,.35);color:white}
.soft-btn{background:#eef5ff;color:var(--primary)}
.hero-board{
  background:rgba(255,255,255,.13);
  border:1px solid rgba(255,255,255,.3);
  border-radius:26px;
  padding:18px;
  display:grid;
  gap:12px;
  align-content:center;
}
.board-line{font-weight:950;font-size:18px}
.board-step{
  background:rgba(255,255,255,.15);
  border-radius:16px;
  padding:14px;
  font-weight:850;
}
.section-head{margin:28px 0 15px}
.section-head h3{font-size:26px;margin:0 0 6px}
.section-head p{margin:0;color:var(--muted)}
.lesson-grid{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:16px;
}
.lesson-card{
  padding:18px;
  background:rgba(255,255,255,.86);
  border:1px solid var(--line);
  border-radius:var(--radius);
  box-shadow:var(--shadow);
  transition:.16s transform;
}
.lesson-card:hover{transform:translateY(-3px)}
.lesson-icon{
  width:50px;height:50px;
  border-radius:18px;
  background:#eaf2ff;
  display:grid;
  place-items:center;
  font-size:25px;
  margin-bottom:13px;
}
.lesson-card h4{margin:0 0 8px;font-size:18px}
.lesson-card p{margin:0;color:var(--muted);font-size:13px;line-height:1.55}
.lesson-card button{margin-top:14px}
.learn-layout{display:grid;grid-template-columns:300px 1fr;gap:18px}
.lesson-list-panel,.lesson-reader,.panel,.coach-card,.tool-card{
  background:rgba(255,255,255,.88);
  border:1px solid var(--line);
  border-radius:var(--radius);
  box-shadow:var(--shadow);
}
.lesson-list-panel{padding:18px;height:max-content;position:sticky;top:20px}
.lesson-list-panel h3{margin-top:0}
.lesson-list{display:grid;gap:8px}
.lesson-list button{
  display:flex;
  align-items:center;
  gap:10px;
  padding:12px;
  border-radius:15px;
  text-align:left;
  background:#f8fbff;
  color:#34405a;
}
.lesson-list button.active,.lesson-list button:hover{background:#eaf2ff;color:var(--primary);font-weight:950}
.lesson-reader{padding:24px}
.reader-head{display:flex;gap:16px;align-items:center;padding-bottom:18px;border-bottom:1px solid var(--line)}
.reader-icon{
  width:62px;height:62px;
  display:grid;place-items:center;
  border-radius:20px;
  background:#eaf2ff;
  font-size:30px;
}
.reader-head h3{font-size:30px;margin:8px 0 0}
.lesson-body{display:grid;gap:16px;margin-top:18px}
.block{
  border:1px solid var(--line);
  border-radius:22px;
  padding:18px;
  background:#fff;
}
.block h4{margin:0 0 10px;font-size:20px}
.block p,.block li{color:#4b5565;line-height:1.75}
.formula{
  background:linear-gradient(135deg,#eef5ff,#ecfeff);
  border-left:6px solid var(--primary);
  font-size:24px;
  font-weight:950;
}
.step-list{display:grid;gap:10px}
.step-item{
  display:grid;
  grid-template-columns:42px 1fr;
  gap:12px;
  align-items:start;
  padding:14px;
  background:#f8fbff;
  border-radius:17px;
}
.step-num{
  width:42px;height:42px;
  display:grid;place-items:center;
  border-radius:14px;
  background:linear-gradient(135deg,var(--primary),var(--primary2));
  color:white;
  font-weight:950;
}
.example-box{
  padding:18px;
  background:#fff7ed;
  border:1px solid #fed7aa;
  border-radius:20px;
}
.panel{padding:22px;margin-bottom:18px}
.panel-head{display:flex;justify-content:space-between;gap:16px;align-items:center}
.panel-head h3{font-size:26px;margin:8px 0 6px}
.panel-head p{margin:0;color:var(--muted);line-height:1.6}
.panel-head select{max-width:360px}
.coach-card{padding:24px}
.coach-top{display:flex;justify-content:space-between;gap:12px;align-items:center;margin-bottom:14px}
#coachTopicBadge{
  background:#ecfeff;
  color:#0e7490;
  border-radius:999px;
  padding:7px 12px;
  font-weight:950;
}
#coachProblem{font-size:28px;line-height:1.45;margin:0 0 18px}
.coach-steps{display:grid;gap:12px;margin-bottom:18px}
.coach-step{
  padding:16px;
  border-radius:19px;
  background:#f8fbff;
  border:1px solid var(--line);
  display:none;
}
.coach-step.show{display:block}
.coach-step strong{display:block;margin-bottom:6px;color:var(--primary)}
.coach-actions{display:flex;gap:12px;flex-wrap:wrap}
.tool-grid{
  display:grid;
  grid-template-columns:repeat(3,minmax(0,1fr));
  gap:16px;
}
.tool-card{padding:20px}
.tool-card h3{margin:0 0 8px}
.tool-card p{color:var(--muted);line-height:1.6}
.inline-inputs{
  display:grid;
  grid-template-columns:1fr auto 1fr;
  gap:10px;
  align-items:center;
  margin:14px 0;
}
.inline-inputs span{text-align:center;font-weight:950;color:#475569}
.wide{width:100%}
.tool-result{
  margin-top:14px;
  border-radius:18px;
  background:#f8fbff;
  padding:14px;
  line-height:1.7;
  color:#34405a;
}
.plan-list{display:grid;gap:12px}
.plan-day{
  display:grid;
  grid-template-columns:86px 1fr;
  gap:14px;
  background:#fff;
  border:1px solid var(--line);
  border-radius:22px;
  padding:16px;
  box-shadow:var(--shadow);
}
.day-badge{
  width:72px;height:72px;
  border-radius:22px;
  display:grid;
  place-items:center;
  background:linear-gradient(135deg,#dbeafe,#cffafe);
  color:var(--primary);
  font-weight:950;
}
.plan-day h4{margin:0 0 7px}
.plan-day p{margin:0;color:var(--muted);line-height:1.6}
.toast{
  position:fixed;
  right:20px;
  bottom:20px;
  background:#111827;
  color:#fff;
  padding:13px 16px;
  border-radius:16px;
  box-shadow:var(--shadow);
}
.hidden{display:none!important}
@media(max-width:980px){
  .app{grid-template-columns:1fr}
  .sidebar{position:relative;height:auto}
  .hero,.learn-layout{grid-template-columns:1fr}
  .lesson-list-panel{position:relative}
  .lesson-grid,.tool-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
  .panel-head{display:grid}
}
@media(max-width:620px){
  .main{padding:16px}
  .topbar{display:grid}
  .lesson-grid,.tool-grid{grid-template-columns:1fr}
  .hero h3{font-size:31px}
  .topbar h2{font-size:30px}
  .plan-day{grid-template-columns:1fr}
  .coach-actions{display:grid}
}