:root {
  color-scheme: dark;
  --bg: #09070a;
  --panel: #131014;
  --panel-2: #1a1217;
  --line: #36202a;
  --text: #f7edf1;
  --muted: #bca9b1;
  --blood: #8f0028;
  --blood-light: #d20b44;
  --blood-bright: #ff315f;
  --success: #55d98a;
  --shadow: 0 22px 60px rgba(0, 0, 0, .35);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 84% 4%, rgba(151, 0, 43, .2), transparent 28rem),
    radial-gradient(circle at 16% 90%, rgba(91, 0, 28, .14), transparent 30rem),
    var(--bg);
  color: var(--text);
  font-family: "Segoe UI Variable", "Segoe UI", system-ui, sans-serif;
}

button, input, select, textarea { font: inherit; }

button, select { cursor: pointer; }

.app-shell { display: grid; grid-template-columns: 284px minmax(0, 1fr); min-height: 100vh; }

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  padding: 28px 20px;
  border-right: 1px solid var(--line);
  background: rgba(12, 8, 11, .93);
  backdrop-filter: blur(18px);
  overflow-y: auto;
  z-index: 5;
}

.brand { display: flex; gap: 12px; align-items: center; margin-bottom: 32px; }
.brand-mark { display: grid; place-items: center; width: 46px; height: 46px; border: 1px solid #d6194f; border-radius: 15px; background: linear-gradient(145deg, #ba073c, #520018); box-shadow: 0 10px 26px rgba(177, 0, 50, .32); font-weight: 900; }
.brand strong, .brand span { display: block; }
.brand strong { font-size: 15px; letter-spacing: .02em; }
.brand span { margin-top: 3px; color: var(--muted); font-size: 12px; }

.course-nav { display: grid; gap: 7px; }
.nav-item { display: grid; grid-template-columns: 36px 1fr auto; gap: 10px; align-items: center; width: 100%; padding: 10px; color: var(--muted); border: 1px solid transparent; border-radius: 13px; background: transparent; text-align: left; transition: .2s ease; }
.nav-item:hover { color: var(--text); border-color: var(--line); background: #171017; }
.nav-item.active { color: #fff; border-color: #72132f; background: linear-gradient(90deg, rgba(155, 0, 42, .34), rgba(91, 0, 29, .12)); }
.nav-icon { display: grid; place-items: center; height: 34px; border-radius: 10px; background: #24141b; color: #ff6d91; font-weight: 850; }
.nav-count { color: #826f77; font-size: 12px; }

.sidebar-panel { margin-top: 28px; padding: 16px; border: 1px solid var(--line); border-radius: 15px; background: #120e12; }
.eyebrow { color: #e73261; font-size: 11px; font-weight: 850; letter-spacing: .13em; text-transform: uppercase; }
.progress-line { height: 7px; margin: 12px 0 9px; overflow: hidden; border-radius: 999px; background: #2c1a22; }
.progress-line span { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg, #800024, #ff2858); transition: width .35s ease; }
.sidebar-panel strong { color: #e8dbe0; font-size: 13px; }

.blood-button, .ghost-button { width: 100%; min-height: 43px; margin-top: 12px; border-radius: 12px; font-weight: 750; }
.blood-button { border: 1px solid #c21747; background: linear-gradient(135deg, #b30739, #710020); color: #fff; box-shadow: 0 12px 30px rgba(152, 0, 42, .25); }
.blood-button:hover { filter: brightness(1.12); }
.ghost-button { border: 1px solid var(--line); background: transparent; color: var(--muted); }
.ghost-button:hover { color: #fff; border-color: #6d3a4d; }

.main-content { width: min(1420px, 100%); padding: 24px clamp(22px, 4vw, 62px) 70px; }
.topbar { display: grid; grid-template-columns: minmax(240px, 1fr) auto auto; gap: 12px; align-items: end; margin-bottom: 24px; }
.search-box { display: flex; align-items: center; gap: 10px; min-height: 48px; padding: 0 15px; border: 1px solid var(--line); border-radius: 14px; background: rgba(22, 16, 21, .82); }
.search-box span { color: #ec2b5b; font-size: 24px; }
.search-box input { width: 100%; border: 0; outline: 0; background: transparent; color: var(--text); }
.search-box input::placeholder { color: #89747d; }
.select-box { display: grid; gap: 4px; color: #a9929c; font-size: 10px; font-weight: 800; letter-spacing: .1em; text-transform: uppercase; }
.select-box select { min-width: 142px; min-height: 48px; padding: 0 36px 0 13px; border: 1px solid var(--line); border-radius: 14px; background: #161015; color: var(--text); }

.hero { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 32px; align-items: center; min-height: 240px; padding: clamp(28px, 5vw, 58px); border: 1px solid #56172b; border-radius: 26px; background: linear-gradient(125deg, rgba(116, 0, 31, .82), rgba(31, 12, 20, .94) 55%, rgba(16, 12, 16, .98)), linear-gradient(45deg, #8c0028, transparent); box-shadow: var(--shadow); overflow: hidden; position: relative; }
.hero::after { content: ""; position: absolute; width: 360px; height: 360px; right: -120px; top: -190px; border: 70px solid rgba(255, 55, 102, .08); border-radius: 50%; }
.hero h1 { max-width: 760px; margin: 12px 0; font-size: clamp(34px, 5vw, 66px); line-height: .98; letter-spacing: -.05em; }
.hero p { max-width: 700px; margin: 0; color: #dac6ce; font-size: 16px; line-height: 1.65; }
.hero-stat { min-width: 160px; padding: 22px; border: 1px solid rgba(255,255,255,.14); border-radius: 20px; background: rgba(9, 6, 9, .32); text-align: center; backdrop-filter: blur(8px); z-index: 1; }
.hero-stat strong, .hero-stat span { display: block; }
.hero-stat strong { font-size: 48px; line-height: 1; }
.hero-stat span { margin-top: 8px; color: #cdb6bf; font-size: 12px; }
.tutor-panel { display: grid; grid-template-columns: minmax(0, 1fr) minmax(320px, .8fr); gap: 24px; align-items: center; margin-top: 22px; padding: 24px; border: 1px solid #552332; border-radius: 20px; background: linear-gradient(135deg, rgba(46, 19, 29, .96), rgba(19, 14, 18, .98)); box-shadow: var(--shadow); }
.tutor-copy h2 { margin: 6px 0 8px; font-size: 25px; }
.tutor-copy p { margin: 0; color: #ceb9c1; line-height: 1.55; }
.tutor-status { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 14px; }
.tutor-status span { padding: 6px 9px; border: 1px solid #59404a; border-radius: 999px; color: #d8c7ce; font-size: 11px; }
.tutor-status .online { border-color: #28603f; color: #8ee0aa; }
.tutor-status .offline { border-color: #6a4d22; color: #e6c27c; }
.tutor-question { display: grid; gap: 8px; }
.tutor-question label { color: #edc6d1; font-size: 12px; font-weight: 800; text-transform: uppercase; letter-spacing: .08em; }
.tutor-question textarea { width: 100%; resize: vertical; box-sizing: border-box; border: 1px solid #52313d; border-radius: 12px; background: #0d090c; color: var(--text); padding: 12px; font: inherit; line-height: 1.45; }
.tutor-question textarea:focus { outline: 2px solid #a92b4d; border-color: transparent; }

section { margin-top: 46px; }
.section-heading { display: flex; justify-content: space-between; gap: 18px; align-items: end; margin-bottom: 17px; }
.section-heading h2 { margin: 4px 0 0; font-size: 28px; letter-spacing: -.03em; }
.muted { color: var(--muted); font-size: 13px; }

.course-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; }
.course-card { position: relative; min-height: 174px; padding: 20px; border: 1px solid var(--line); border-radius: 18px; background: linear-gradient(145deg, #191218, #100d10); color: inherit; text-align: left; overflow: hidden; transition: transform .2s ease, border-color .2s ease; }
.course-card:hover { transform: translateY(-3px); border-color: #7d2942; }
.course-card.active { border-color: #b40c3d; box-shadow: inset 0 0 0 1px rgba(211, 14, 68, .2), 0 14px 38px rgba(100, 0, 29, .16); }
.course-card::after { content: attr(data-icon); position: absolute; right: 12px; bottom: -15px; color: rgba(242, 43, 94, .07); font-size: 88px; font-weight: 900; }
.course-card h3 { max-width: 82%; margin: 20px 0 8px; font-size: 19px; }
.course-card p { max-width: 88%; margin: 0; color: #af9ba4; font-size: 13px; line-height: 1.45; }
.course-meta { display: flex; justify-content: space-between; align-items: center; color: #d8c8cf; font-size: 12px; }
.course-dot { width: 8px; height: 8px; border-radius: 50%; background: #e51850; box-shadow: 0 0 14px #e51850; }

.exercise-list { display: grid; gap: 12px; }
.exercise-card { border: 1px solid var(--line); border-radius: 17px; background: rgba(20, 15, 19, .9); overflow: hidden; transition: border-color .2s ease; }
.exercise-card.completed { border-color: rgba(85, 217, 138, .45); }
.exercise-card.random-focus { animation: pulse-card 1.4s ease; }
@keyframes pulse-card { 0%,100% { box-shadow: none; } 35% { box-shadow: 0 0 0 3px rgba(255,49,95,.28), 0 0 42px rgba(202,0,55,.35); } }
.exercise-head { display: grid; grid-template-columns: auto minmax(0, 1fr) auto; gap: 14px; align-items: start; padding: 18px; }
.complete-check { display: grid; place-items: center; width: 26px; height: 26px; margin-top: 2px; border: 1px solid #684050; border-radius: 8px; background: #110d10; color: transparent; }
.complete-check.checked { color: #08130d; border-color: var(--success); background: var(--success); }
.exercise-title h3 { margin: 0 0 7px; font-size: 17px; }
.badges { display: flex; flex-wrap: wrap; gap: 7px; }
.badge { padding: 4px 8px; border: 1px solid #432633; border-radius: 999px; color: #baa5ae; background: #1b1117; font-size: 10px; font-weight: 750; }
.badge.level-advanced { color: #ff6f91; border-color: #752038; }
.exercise-course { color: #e33160; font-size: 12px; font-weight: 800; }
.exercise-body { padding: 0 18px 18px 58px; }
.prompt { margin: 0; color: #e7dce1; line-height: 1.65; white-space: pre-wrap; }
.exercise-actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 16px; }
.small-button { padding: 8px 11px; border: 1px solid #523040; border-radius: 10px; background: #1b1117; color: #d8c7ce; font-size: 12px; font-weight: 750; }
.small-button:hover { color: #fff; border-color: #9a3150; }
.reveal { display: none; margin-top: 13px; padding: 15px; border-left: 3px solid var(--blood-light); border-radius: 5px 12px 12px 5px; background: #1c1016; color: #d9c7ce; line-height: 1.6; white-space: pre-wrap; }
.reveal.visible { display: block; }
.reveal.hint { border-left-color: #8c6b24; background: #19150e; }
.code-like { font-family: Consolas, "Cascadia Code", monospace; font-size: 13px; }
.katex { color: #fff7fa; font-size: 1.08em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 8px 2px; margin: 8px 0; }
.prompt .katex, .reveal .katex { white-space: normal; }
.ai-button { border-color: #7e2842; background: #30101c; color: #ffd5e0; }
.notes-area { width: 100%; min-height: 82px; margin-top: 13px; padding: 12px; resize: vertical; border: 1px solid #3b2630; border-radius: 11px; outline: 0; background: #0f0c0f; color: var(--text); line-height: 1.45; }
.notes-area:focus { border-color: #a80b3b; box-shadow: 0 0 0 3px rgba(177, 0, 49, .14); }
.empty-state, .material-panel { padding: 28px; border: 1px dashed #4a2e39; border-radius: 17px; background: rgba(20, 14, 18, .55); color: var(--muted); }
.material-intro { margin: 0 0 18px; line-height: 1.55; }
.material-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 9px; }
.material-link { display: grid; grid-template-columns: 42px minmax(0,1fr) auto; gap: 11px; align-items: center; padding: 11px; border: 1px solid #37242d; border-radius: 12px; background: #120e11; color: #e7d9df; text-decoration: none; }
.material-link:hover { border-color: #8d2a48; background: #1a1116; }
.file-type { display: grid; place-items: center; height: 34px; border-radius: 9px; background: #2b1520; color: #ff557c; font-size: 10px; font-weight: 900; }
.file-name { min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; font-size: 12px; }
.file-size { color: #856f78; font-size: 10px; }

.toast { position: fixed; right: 24px; bottom: 24px; max-width: 360px; padding: 13px 16px; border: 1px solid #932947; border-radius: 12px; background: #250f18; color: #fff; box-shadow: var(--shadow); opacity: 0; transform: translateY(12px); pointer-events: none; transition: .2s ease; z-index: 20; }
.toast.visible { opacity: 1; transform: translateY(0); }

@media (max-width: 1050px) {
  .app-shell { grid-template-columns: 1fr; }
  .sidebar { position: relative; height: auto; padding: 18px; border-right: 0; border-bottom: 1px solid var(--line); }
  .brand { margin-bottom: 14px; }
  .course-nav { grid-template-columns: repeat(4, minmax(150px, 1fr)); overflow-x: auto; padding-bottom: 5px; }
  .sidebar-panel, .sidebar > .blood-button, .sidebar > .ghost-button { display: none; }
  .main-content { padding-top: 20px; }
  .course-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 720px) {
  .main-content { padding-inline: 15px; }
  .topbar { grid-template-columns: 1fr 1fr; }
  .search-box { grid-column: 1 / -1; }
  .select-box select { min-width: 0; width: 100%; }
  .hero { grid-template-columns: 1fr; padding: 28px 22px; }
  .tutor-panel { grid-template-columns: 1fr; padding: 20px; }
  .hero-stat { text-align: left; }
  .course-grid, .material-grid { grid-template-columns: 1fr; }
  .exercise-head { grid-template-columns: auto 1fr; }
  .exercise-course { grid-column: 2; }
  .exercise-body { padding-left: 18px; }
  .section-heading { align-items: start; }
}