:root {
  color-scheme: light;
  --ink: #1c1c1e;
  --muted: #6e6e73;
  --soft: #f2f2f7;
  --card: #ffffff;
  --line: rgba(60, 60, 67, 0.12);
  --blue: #0071e3;
  --blue-soft: #eaf3ff;
  --green: #248a3d;
  --green-soft: #eaf7ed;
  --orange: #bf5b00;
  --orange-soft: #fff1e3;
  --red: #d70015;
  --purple: #7d4bc7;
  --shadow: 0 16px 45px rgba(0, 0, 0, 0.07);
  --shadow-soft: 0 6px 22px rgba(0, 0, 0, 0.045);
  --radius: 20px;
}

* { box-sizing: border-box; }

html { background: var(--soft); }

body {
  margin: 0;
  min-width: 320px;
  min-height: 100vh;
  color: var(--ink);
  background: var(--soft);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

.boot-screen {
  min-height: 100vh;
  display: grid;
  place-content: center;
  justify-items: center;
  gap: 14px;
  color: var(--muted);
}

.brand-mark {
  width: 58px;
  height: 58px;
  display: grid;
  place-items: center;
  color: white;
  background: transparent;
  border-radius: 17px;
  filter: drop-shadow(0 12px 18px rgba(0, 113, 227, .28));
}
.crystal-logo { display: block; width: 100%; height: 100%; overflow: visible; }
.crystal-logo .gem-c { fill: rgba(255,255,255,.97); }
.crystal-logo .gem-facet { fill: rgba(255,255,255,.34); }
.crystal-logo .gem-shine { fill: none; stroke: rgba(255,255,255,.25); stroke-width: .8; }

.app-shell { min-height: 100vh; }

.sidebar {
  position: fixed;
  inset: 0 auto 0 0;
  z-index: 30;
  width: 232px;
  padding: 24px 16px;
  border-right: 1px solid var(--line);
  background: rgba(248, 248, 250, 0.88);
  backdrop-filter: blur(30px) saturate(160%);
}

.brand {
  display: flex;
  align-items: center;
  gap: 11px;
  padding: 0 9px 26px;
}

.brand .brand-mark {
  width: 38px;
  height: 38px;
  border-radius: 11px;
  font-size: 20px;
}

.brand-copy strong { display: block; font-size: 17px; }
.brand-copy span { color: var(--muted); font-size: 12px; }

.nav-list { display: grid; gap: 4px; }

.nav-button {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: 44px;
  padding: 10px 12px;
  border: 0;
  border-radius: 11px;
  background: transparent;
  color: #525257;
  text-align: left;
  cursor: pointer;
  transition: 160ms ease;
}

.nav-button:disabled {
  opacity: .38;
  cursor: not-allowed;
}

.nav-button:hover { background: rgba(0, 0, 0, 0.04); }
.nav-button.active { color: var(--blue); background: rgba(0, 113, 227, 0.09); font-weight: 650; }
.nav-button svg { width: 21px; height: 21px; }
button:focus-visible, input:focus-visible, select:focus-visible {
  outline: 3px solid rgba(0,113,227,.32);
  outline-offset: 2px;
}

.sidebar-profile {
  position: absolute;
  inset: auto 18px 22px;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 15px;
  background: rgba(255,255,255,.6);
}

.avatar {
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  color: white;
  background: linear-gradient(145deg, #7d4bc7, #4f2aa1);
  font-weight: 700;
}

.sidebar-profile strong, .sidebar-profile span { display: block; }
.sidebar-profile strong { max-width: 140px; overflow: hidden; text-overflow: ellipsis; font-size: 13px; }
.sidebar-profile span { color: var(--muted); font-size: 11px; }

.main {
  margin-left: 232px;
  padding: 42px clamp(28px, 4vw, 58px) 96px;
}

.page { max-width: 1160px; margin: 0 auto; animation: fade-in 180ms ease; }
@keyframes fade-in { from { opacity: 0; transform: translateY(5px); } }

.eyebrow {
  margin: 0 0 8px;
  color: var(--blue);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .04em;
  text-transform: uppercase;
}

.page-title {
  margin: 0;
  font-size: clamp(34px, 4vw, 46px);
  line-height: 1.06;
  letter-spacing: -.04em;
}

.page-subtitle {
  max-width: 680px;
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 16px;
  line-height: 1.48;
}

.top-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 22px;
  margin-bottom: 30px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 44px;
  padding: 0 18px;
  border: 0;
  border-radius: 999px;
  background: var(--blue);
  color: white;
  font-size: 14px;
  font-weight: 650;
  cursor: pointer;
  transition: transform 140ms ease, filter 140ms ease;
}

.button:hover { filter: brightness(.94); }
.button:active { transform: scale(.98); }
.button.secondary { color: var(--blue); background: var(--blue-soft); }
.button.neutral { color: var(--ink); background: #e9e9ee; }
.button.danger { color: var(--red); background: #ffe8eb; }
.button.small { min-height: 34px; padding: 0 13px; font-size: 13px; }

.hero {
  position: relative;
  overflow: hidden;
  min-height: 280px;
  display: grid;
  align-items: center;
  grid-template-columns: minmax(0, 1.25fr) minmax(250px, .75fr);
  gap: 30px;
  padding: clamp(30px, 4.5vw, 48px);
  border-radius: 30px;
  color: white;
  background: linear-gradient(128deg, #12283d, #0868bf 62%, #42a8f5);
  box-shadow: 0 24px 60px rgba(4, 67, 123, .2);
}

.hero::after {
  content: "";
  position: absolute;
  width: 430px;
  height: 430px;
  right: -170px;
  top: -260px;
  border: 70px solid rgba(255,255,255,.11);
  border-radius: 50%;
}

.hero h1 { max-width: 700px; margin: 0; font-size: clamp(36px, 4.5vw, 54px); line-height: 1; letter-spacing: -.047em; }
.hero p { max-width: 650px; margin: 18px 0 25px; color: rgba(255,255,255,.78); font-size: 17px; line-height: 1.5; }
.hero .button { color: #0068ce; background: white; }

.preparedness { position: relative; z-index: 1; display: grid; justify-items: center; gap: 12px; }
.score-ring {
  --score: 0;
  width: 160px;
  height: 160px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: conic-gradient(white calc(var(--score) * 1%), rgba(255,255,255,.2) 0);
}
.score-ring::before { content: ""; width: 128px; height: 128px; border-radius: 50%; background: #1378ca; }
.score-ring strong { position: absolute; font-size: 38px; letter-spacing: -.04em; }
.preparedness span { color: rgba(255,255,255,.72); font-size: 13px; }

.stat-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin: 16px 0 24px; }
.card {
  border: 1px solid rgba(60,60,67,.08);
  border-radius: var(--radius);
  background: var(--card);
  box-shadow: var(--shadow-soft);
}
.stat-card { padding: 18px; }
.stat-card .label { color: var(--muted); font-size: 13px; }
.stat-card strong { display: block; margin-top: 7px; font-size: 27px; letter-spacing: -.03em; }
.stat-card .delta { margin-top: 7px; color: var(--green); font-size: 12px; }

.section-grid { display: grid; grid-template-columns: 1.08fr .92fr; gap: 14px; margin-top: 14px; }
.panel { padding: 24px; }
.panel h2 { margin: 0 0 5px; font-size: 21px; letter-spacing: -.025em; }
.panel-intro { margin: 0 0 19px; color: var(--muted); font-size: 14px; line-height: 1.45; }

.recommendation {
  padding: 18px;
  border-radius: 18px;
  background: linear-gradient(145deg, var(--blue-soft), #f5f9ff);
}
.recommendation .tag { color: var(--blue); font-size: 12px; font-weight: 700; text-transform: uppercase; }
.recommendation h3 { margin: 7px 0 6px; font-size: 17px; }
.recommendation p { margin: 0 0 15px; color: #4b5e72; font-size: 14px; line-height: 1.48; }

.activity-list { display: grid; gap: 13px; }
.activity-row { display: flex; gap: 12px; align-items: center; }
.activity-dot { width: 10px; height: 10px; flex: 0 0 auto; border-radius: 50%; background: var(--blue); box-shadow: 0 0 0 5px var(--blue-soft); }
.activity-row strong { display: block; font-size: 14px; }
.activity-row span { color: var(--muted); font-size: 12px; }

.teach-layout { display: grid; grid-template-columns: 196px minmax(0, 1fr); gap: 16px; }
.slide-browser { position: sticky; top: 20px; height: calc(100vh - 40px); overflow: hidden; display: flex; flex-direction: column; }
.browser-head { padding: 18px 18px 13px; border-bottom: 1px solid var(--line); }
.search {
  width: 100%;
  height: 39px;
  padding: 0 13px;
  border: 1px solid transparent;
  border-radius: 11px;
  outline: none;
  background: #eeeeF2;
}
.search:focus { border-color: rgba(0,113,227,.35); background: white; }
.slide-list { padding: 8px; overflow: auto; }
.slide-item { width: 100%; padding: 11px; border: 0; border-radius: 13px; background: transparent; text-align: left; cursor: pointer; }
.slide-item:hover { background: rgba(0,0,0,.035); }
.slide-item.active { background: var(--blue-soft); }
.slide-item .number { display: block; margin-bottom: 4px; color: var(--blue); font-size: 11px; font-weight: 700; }
.slide-item strong { display: -webkit-box; overflow: hidden; font-size: 13px; line-height: 1.25; -webkit-box-orient: vertical; -webkit-line-clamp: 2; }
.slide-item span:last-child { display: block; margin-top: 4px; color: var(--muted); font-size: 11px; }

.lesson { min-width: 0; }
.mobile-study-tools { display: none; }
.teach-toolbar {
  position: sticky;
  top: 12px;
  z-index: 20;
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr) 42px auto;
  gap: 8px;
  align-items: center;
  margin-bottom: 12px;
  padding: 8px;
  background: rgba(255,255,255,.9);
}
.teach-toolbar label { min-width: 0; display: grid; gap: 1px; padding: 2px 7px; }
.teach-toolbar label span { color: var(--muted); font-size: 9px; font-weight: 700; text-transform: uppercase; }
.teach-toolbar select { min-width: 0; width: 100%; border: 0; outline: 0; background: transparent; font-weight: 650; }
.toolbar-step { height: 38px; border: 0; border-radius: 11px; color: var(--blue); background: var(--blue-soft); font-size: 25px; cursor: pointer; }
.toolbar-step:disabled { color: #aaaab0; opacity: .5; }
.study-split { display: grid; grid-template-columns: minmax(420px, 1.12fr) minmax(350px, .88fr); gap: 18px; align-items: start; }
.slide-column { position: sticky; top: 78px; min-width: 0; }
.slide-column-caption { display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 9px 7px 0; color: var(--muted); font-size: 11px; }
.notes-column { min-width: 0; }
.slide-frame { overflow: hidden; padding: 8px; }
.slide-image { display: block; width: 100%; height: auto; max-height: 66vh; aspect-ratio: 4/3; object-fit: contain; border-radius: 14px; background: #eee; }
.slide-placeholder { width: 100%; aspect-ratio: 4/3; display: grid; place-content: center; border-radius: 17px; background: #eee; color: var(--muted); }
.lesson-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 16px; padding: 2px 4px 13px; }
.lesson-head h2 { max-width: 850px; margin: 3px 0 0; font-size: clamp(20px, 2vw, 27px); line-height: 1.18; letter-spacing: -.025em; }
.lesson-head .slide-index { color: var(--blue); font-size: 10px; font-weight: 750; text-transform: uppercase; }

.lesson-sections { display: grid; gap: 9px; }
.lesson-block { padding: 17px 18px; }
.lesson-block h3 { display: flex; align-items: center; gap: 9px; margin: 0 0 10px; font-size: 15px; }
.lesson-block p, .lesson-block li { color: #424247; font-size: 13px; line-height: 1.52; }
.lesson-block ul { margin: 0; padding-left: 20px; }
.lesson-block li + li { margin-top: 6px; }
.lesson-block.blue { background: linear-gradient(145deg, #eff7ff, white); }
.lesson-block.orange { background: linear-gradient(145deg, #fff5e9, white); }
.lesson-block.green { background: linear-gradient(145deg, #eff9f1, white); }
.line-explanation { padding: 11px 0; border-top: 1px solid var(--line); }
.line-explanation:first-of-type { border-top: 0; padding-top: 0; }
.line-explanation strong { display: block; margin-bottom: 4px; color: var(--ink); font-size: 12px; line-height: 1.4; }
.line-explanation p { margin: 0; }

.slide-note-editor { margin-top: 12px; padding: 16px; }
.slide-note-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 12px; margin-bottom: 10px; }
.slide-note-head span { color: var(--muted); font-size: 10px; font-weight: 700; text-transform: uppercase; }
.slide-note-head strong { display: block; margin-top: 2px; font-size: 14px; }
.slide-note-head > span { font-size: 10px; font-weight: 600; text-transform: none; }
.slide-note-editor textarea {
  width: 100%;
  min-height: 118px;
  padding: 12px 13px;
  resize: vertical;
  border: 1px solid var(--line);
  border-radius: 12px;
  outline: none;
  color: var(--ink);
  background: #fafafd;
  font: inherit;
  font-size: 13px;
  line-height: 1.5;
}
.slide-note-editor textarea:focus { border-color: rgba(0,113,227,.45); background: white; box-shadow: 0 0 0 3px var(--blue-soft); }
.text-link { padding: 9px 0 0; border: 0; color: var(--blue); background: transparent; font-size: 12px; font-weight: 700; cursor: pointer; }

.lecture-notes-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.lecture-note-card { overflow: hidden; }
.lecture-note-card button { width: 100%; min-height: 220px; display: flex; flex-direction: column; padding: 22px; border: 0; color: inherit; background: transparent; text-align: left; cursor: pointer; }
.lecture-note-card button:hover { background: var(--blue-soft); }
.lecture-note-card span { color: var(--blue); font-size: 10px; font-weight: 750; text-transform: uppercase; }
.lecture-note-card h2 { margin: 7px 0 10px; font-size: 19px; line-height: 1.25; letter-spacing: -.02em; }
.lecture-note-card p { display: -webkit-box; overflow: hidden; margin: 0 0 18px; color: var(--muted); font-size: 13px; line-height: 1.55; white-space: pre-wrap; -webkit-box-orient: vertical; -webkit-line-clamp: 5; }
.lecture-note-card strong { margin-top: auto; color: var(--blue); font-size: 12px; }
.notes-empty { max-width: 680px; margin: 40px auto 0; padding: 48px 30px; text-align: center; }
.notes-empty-icon { width: 54px; height: 54px; display: grid; place-items: center; margin: 0 auto 16px; border-radius: 17px; color: var(--blue); background: var(--blue-soft); }
.notes-empty-icon svg { width: 25px; height: 25px; }
.notes-empty h2 { margin: 0 0 8px; font-size: 24px; }
.notes-empty p { max-width: 470px; margin: 0 auto 20px; color: var(--muted); font-size: 14px; line-height: 1.5; }

.source-badge { display: inline-flex; align-items: center; gap: 6px; padding: 6px 10px; border-radius: 999px; color: #57575d; background: #ececf0; font-size: 11px; font-weight: 650; }
.grounding-note { margin-top: 14px; padding: 12px 14px; border-radius: 12px; color: #5a5147; background: #fff8e9; font-size: 12px; line-height: 1.45; }

.slide-lightbox {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: none;
  place-content: center;
  gap: 12px;
  padding: 18px;
  color: white;
  background: rgba(0, 0, 0, .88);
  backdrop-filter: blur(14px);
}
.slide-lightbox.open { display: grid; }
.slide-lightbox img { display: block; width: min(100%, 1000px); max-height: 82vh; object-fit: contain; border-radius: 14px; background: #ddd; }
.slide-lightbox > span { text-align: center; font-size: 13px; }
.lightbox-close {
  position: fixed;
  top: max(16px, env(safe-area-inset-top));
  right: 16px;
  width: 42px;
  height: 42px;
  border: 0;
  border-radius: 50%;
  color: white;
  background: rgba(255,255,255,.18);
  font-size: 29px;
  line-height: 1;
  cursor: pointer;
}
body.lightbox-open { overflow: hidden; }

.mode-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
.mode-card { min-height: 164px; padding: 19px; display: flex; flex-direction: column; align-items: flex-start; text-align: left; cursor: pointer; transition: transform 160ms ease, box-shadow 160ms ease, border-color 160ms ease; }
.mode-card:hover { transform: translateY(-2px); border-color: rgba(0,113,227,.18); box-shadow: var(--shadow); }
.mode-icon { width: 45px; height: 45px; display: grid; place-items: center; border-radius: 14px; color: var(--blue); background: var(--blue-soft); font-size: 21px; font-weight: 700; }
.mode-copy { min-width: 0; display: flex; flex: 1; flex-direction: column; }
.mode-card h3 { margin: 15px 0 6px; font-size: 18px; }
.mode-card p { margin: 0 0 18px; color: var(--muted); font-size: 13px; line-height: 1.45; }
.mode-card span { margin-top: auto; color: var(--blue); font-size: 13px; font-weight: 650; }
.mode-card.compact { min-height: 88px; flex-direction: row; align-items: center; gap: 13px; padding: 14px; }
.mode-card.compact .mode-icon { width: 39px; height: 39px; flex: 0 0 auto; border-radius: 12px; font-size: 16px; }
.mode-card.compact h3 { margin: 0 0 3px; font-size: 15px; }
.mode-card.compact p { overflow: hidden; margin: 0 0 4px; font-size: 11px; text-overflow: ellipsis; white-space: nowrap; }
.mode-card.compact span { margin: 0; font-size: 11px; }
.custom-practice { display: grid; grid-template-columns: .8fr 1.2fr; gap: 24px; align-items: center; margin-top: 14px; padding: 24px; }
.custom-practice h2 { margin: 0 0 6px; font-size: 22px; }
.custom-practice p { margin: 0; color: var(--muted); font-size: 14px; }
.custom-controls { display: grid; grid-template-columns: 1.4fr 1fr .7fr auto; gap: 10px; align-items: end; }
.custom-controls label { min-width: 0; display: grid; gap: 6px; }
.custom-controls label > span { color: var(--muted); font-size: 11px; font-weight: 700; text-transform: uppercase; }
.custom-controls select { min-width: 0; height: 42px; padding: 0 10px; border: 1px solid var(--line); border-radius: 11px; background: white; }

.quiz-shell { max-width: 820px; margin: 0 auto; }
.quiz-progress { height: 6px; overflow: hidden; margin: 20px 0 30px; border-radius: 99px; background: #dddde2; }
.quiz-progress span { display: block; height: 100%; border-radius: inherit; background: var(--blue); transition: width 220ms ease; }
.question-card { padding: clamp(24px, 4vw, 34px); }
.question-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 17px; }
.question-card h2 { margin: 0 0 24px; font-size: clamp(22px, 4vw, 30px); line-height: 1.25; letter-spacing: -.025em; }
.question-tools { display: flex; flex-wrap: wrap; gap: 8px; margin: -4px 0 18px; }
.study-tool { min-height: 34px; padding: 0 12px; border: 1px solid var(--line); border-radius: 999px; color: var(--muted); background: white; cursor: pointer; }
.study-tool.active { color: var(--blue); border-color: rgba(0,113,227,.28); background: var(--blue-soft); font-weight: 650; }
.choices { display: grid; gap: 10px; }
.choice {
  width: 100%;
  display: grid;
  grid-template-columns: 30px 1fr;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 15px;
  background: white;
  text-align: left;
  cursor: pointer;
}
.choice:hover { border-color: rgba(0,113,227,.4); background: #f8fbff; }
.choice.selected { border-color: var(--blue); background: var(--blue-soft); }
.choice.correct { border-color: var(--green); background: var(--green-soft); }
.choice.incorrect { border-color: var(--red); background: #fff0f1; }
.choice-letter { width: 28px; height: 28px; display: grid; place-items: center; border-radius: 50%; background: #eeeef2; font-size: 12px; font-weight: 700; }
.rationale { margin-top: 19px; padding: 19px; border-radius: 16px; background: #f3f8ff; }
.rationale strong { color: var(--blue); }
.rationale p { margin: 7px 0 0; color: #42566d; font-size: 14px; line-height: 1.55; }
.quiz-actions { display: flex; justify-content: space-between; gap: 12px; margin-top: 20px; }
.summary-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin: 28px 0 18px; }
.session-guidance { padding: 25px; }
.session-guidance h2 { margin: 0 0 8px; }
.session-guidance p { margin: 0; color: var(--muted); line-height: 1.55; }
.summary-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 20px; }

.flashcard-wrap { max-width: 760px; margin: 0 auto; }
.session-header {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 14px;
  margin-bottom: 14px;
}
.session-count { display: grid; justify-items: center; gap: 2px; }
.session-count span { color: var(--muted); font-size: 11px; font-weight: 650; text-transform: uppercase; letter-spacing: .04em; }
.session-count strong { font-size: 15px; }
.back-button, .flag-button, .control-button {
  min-height: 40px;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 0 13px;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: #3a3a3c;
  background: rgba(255,255,255,.82);
  cursor: pointer;
}
.back-button { justify-self: start; }
.flag-button { justify-self: end; }
.control-button { justify-self: start; }
.flag-button.active { color: #9a5a00; border-color: rgba(191,91,0,.22); background: var(--orange-soft); }
.control-button:disabled { opacity: .38; cursor: default; }
.session-progress { height: 5px; overflow: hidden; margin-bottom: 18px; border-radius: 999px; background: #dedee3; }
.session-progress span { display: block; height: 100%; border-radius: inherit; background: var(--blue); }
.flashcard-stage { perspective: 1200px; }
.flashcard {
  width: 100%;
  min-height: 410px;
  display: grid;
  place-content: center;
  padding: 54px;
  border: 0;
  text-align: center;
  cursor: pointer;
  box-shadow: 0 18px 55px rgba(0,0,0,.075);
  transition: transform 180ms ease, box-shadow 180ms ease;
}
.flashcard:hover { transform: translateY(-2px); box-shadow: 0 24px 65px rgba(0,0,0,.09); }
.flashcard.answer-side { background: linear-gradient(155deg, #f5faff, #fff); }
.flashcard .hint { margin-bottom: 20px; color: var(--blue); font-size: 11px; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; }
.flashcard h2 { max-width: 650px; margin: 0 auto; font-size: clamp(25px, 3.5vw, 34px); line-height: 1.28; letter-spacing: -.025em; }
.flashcard p { max-width: 620px; margin: 15px auto 0; color: var(--muted); line-height: 1.6; }
.flashcard .card-instruction { font-size: 13px; }
.flashcard-controls { min-height: 54px; display: grid; grid-template-columns: 1fr auto; align-items: center; gap: 14px; margin-top: 14px; }
.rating-actions { display: grid; grid-template-columns: auto auto; gap: 9px; }
.rating-actions .button { min-width: 132px; min-height: 44px; }

.analytics-grid { display: grid; grid-template-columns: repeat(12, 1fr); gap: 14px; }
.analytics-grid .wide { grid-column: span 8; }
.analytics-grid .narrow { grid-column: span 4; }
.analytics-grid .full { grid-column: 1 / -1; }
.metric-big { font-size: 54px; font-weight: 750; letter-spacing: -.055em; }
.bar-list { display: grid; gap: 15px; margin-top: 22px; }
.bar-label { display: flex; justify-content: space-between; margin-bottom: 7px; font-size: 13px; }
.bar-track { height: 8px; overflow: hidden; border-radius: 99px; background: #e4e4e8; }
.bar-track span { display: block; height: 100%; border-radius: inherit; background: linear-gradient(90deg, #0071e3, #55aaff); }
.empty-state { padding: 36px; color: var(--muted); text-align: center; }

.settings-stack { max-width: 820px; display: grid; gap: 12px; }
.setting-card { padding: 24px; }
.setting-card h2 { margin: 0 0 7px; font-size: 19px; }
.setting-card p { margin: 0 0 18px; color: var(--muted); font-size: 14px; line-height: 1.5; }
.field { display: grid; gap: 7px; margin-bottom: 14px; }
.field label { color: var(--muted); font-size: 12px; font-weight: 650; }
.field input, .field select { height: 43px; padding: 0 13px; border: 1px solid var(--line); border-radius: 11px; outline: none; background: white; }
.field input:focus, .field select:focus { border-color: var(--blue); }

.library-layout { display: grid; grid-template-columns: minmax(0, 1.35fr) minmax(330px, .65fr); gap: 18px; align-items: start; }
.section-heading { min-height: 46px; display: flex; align-items: center; justify-content: space-between; padding: 0 3px 10px; }
.section-heading span, .section-heading strong { display: block; }
.section-heading span { color: var(--muted); font-size: 11px; font-weight: 700; letter-spacing: .05em; text-transform: uppercase; }
.section-heading strong { margin-top: 3px; font-size: 17px; }
.lecture-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }
.lecture-card { position: relative; overflow: hidden; min-height: 190px; }
.lecture-card.active { border-color: rgba(0,113,227,.26); box-shadow: 0 12px 35px rgba(0,91,184,.1); }
.lecture-open { width: 100%; height: 100%; min-height: 190px; display: flex; flex-direction: column; align-items: flex-start; padding: 22px; border: 0; background: transparent; text-align: left; cursor: pointer; }
.lecture-subject { color: var(--blue); font-size: 11px; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; }
.lecture-open h2 { max-width: calc(100% - 48px); margin: 11px 0 8px; font-size: 22px; line-height: 1.12; letter-spacing: -.025em; }
.lecture-open p { margin: 0; color: var(--muted); font-size: 12px; line-height: 1.45; }
.lecture-action { margin-top: auto; padding-top: 20px; color: var(--blue); font-size: 12px; font-weight: 700; }
.lecture-delete { position: absolute; top: 13px; right: 13px; min-height: 30px; padding: 0 9px; border: 0; border-radius: 999px; color: var(--red); background: #fff0f1; font-size: 11px; cursor: pointer; }
.empty-library { grid-column: 1 / -1; padding: 40px; text-align: center; }
.empty-library h2 { margin: 0 0 7px; }
.empty-library p { margin: 0; color: var(--muted); }
.upload-card { position: sticky; top: 20px; padding: 25px; }
.upload-icon { width: 48px; height: 48px; display: grid; place-items: center; margin-bottom: 20px; border-radius: 15px; color: var(--blue); background: var(--blue-soft); font-size: 29px; font-weight: 300; }
.upload-card h2 { margin: 0 0 8px; font-size: 25px; letter-spacing: -.03em; }
.upload-intro { margin: 0 0 22px; color: var(--muted); font-size: 13px; line-height: 1.5; }
.upload-card .field { margin-bottom: 13px; }
.upload-card .field > span { color: var(--muted); font-size: 11px; font-weight: 700; text-transform: uppercase; }
.upload-card .field small { color: var(--muted); font-size: 11px; line-height: 1.35; }
.upload-card .field input, .upload-card .field select { width: 100%; height: 44px; padding: 0 12px; border: 1px solid var(--line); border-radius: 12px; outline: 0; background: #fff; }
.file-field { position: relative; display: grid; gap: 7px; margin-bottom: 12px; }
.file-field > span { color: var(--muted); font-size: 11px; font-weight: 700; text-transform: uppercase; }
.file-field small { font-weight: 500; text-transform: none; }
.file-field input { position: absolute; width: 1px; height: 1px; opacity: 0; pointer-events: none; }
.file-field strong { min-height: 46px; display: flex; align-items: center; overflow: hidden; padding: 0 13px; border: 1px dashed rgba(0,113,227,.35); border-radius: 12px; color: var(--blue); background: #f7fbff; font-size: 12px; text-overflow: ellipsis; white-space: nowrap; cursor: pointer; }
.file-field:focus-within strong { outline: 3px solid rgba(0,113,227,.22); }
.upload-submit { width: 100%; margin-top: 4px; }
.upload-progress { margin-top: 17px; padding: 14px; border-radius: 14px; background: #f2f7fd; }
.upload-progress > div:first-child { display: flex; justify-content: space-between; gap: 12px; font-size: 12px; }
.progress-track { height: 6px; overflow: hidden; margin-top: 10px; border-radius: 999px; background: #d9e5f2; }
.progress-track span { display: block; width: 0; height: 100%; border-radius: inherit; background: var(--blue); transition: width 180ms ease; }
.upload-progress p, .privacy-note { color: var(--muted); font-size: 11px; line-height: 1.45; }
.upload-progress p { margin: 9px 0 0; }
.privacy-note { margin: 18px 0 0; }

.mobile-nav { display: none; }

.ask-clarity-fab {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 45;
  display: flex;
  align-items: center;
  gap: 8px;
  min-height: 48px;
  padding: 7px 15px 7px 8px;
  border: 1px solid rgba(0,113,227,.16);
  border-radius: 999px;
  color: #075cae;
  background: rgba(255,255,255,.92);
  box-shadow: 0 12px 38px rgba(0,70,140,.18);
  backdrop-filter: blur(22px);
  font-weight: 700;
  cursor: pointer;
}
.ask-clarity-fab .crystal-logo { width: 34px; height: 34px; }
.tutor-scrim { position: fixed; inset: 0; z-index: 70; display: none; background: rgba(10,18,28,.28); backdrop-filter: blur(4px); }
.tutor-scrim.open { display: block; }
.tutor-panel {
  position: fixed;
  inset: 0 0 0 auto;
  z-index: 71;
  width: min(440px, 94vw);
  display: grid;
  grid-template-rows: auto auto 1fr auto;
  padding: 20px;
  background: #f7f7f9;
  box-shadow: -20px 0 60px rgba(0,0,0,.16);
  transform: translateX(105%);
  transition: transform 220ms ease;
}
.tutor-panel.open { transform: translateX(0); }
.tutor-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 15px; }
.tutor-head h2 { margin: 0; font-size: 28px; letter-spacing: -.04em; }
.tutor-close { width: 38px; height: 38px; border: 0; border-radius: 50%; background: #e7e7eb; font-size: 25px; cursor: pointer; }
.tutor-boundary { margin: 16px 0; padding: 11px 13px; border-radius: 13px; color: #315778; background: #e8f3ff; font-size: 12px; line-height: 1.45; }
.tutor-messages { min-height: 0; overflow: auto; display: grid; align-content: start; gap: 12px; padding: 4px 2px 18px; }
.tutor-welcome { padding: 22px; border: 1px solid var(--line); border-radius: 18px; background: white; }
.tutor-welcome p { margin: 7px 0 0; color: var(--muted); font-size: 13px; line-height: 1.5; }
.tutor-message { max-width: 90%; padding: 12px 14px; border-radius: 16px; background: white; box-shadow: 0 5px 18px rgba(0,0,0,.04); }
.tutor-message.user { justify-self: end; color: white; background: var(--blue); }
.tutor-message > span { display: block; margin-bottom: 4px; opacity: .72; font-size: 10px; font-weight: 750; text-transform: uppercase; }
.tutor-message p { margin: 0; font-size: 13px; line-height: 1.5; white-space: pre-line; }
.tutor-message small { display: block; margin-top: 7px; color: var(--blue); font-size: 10px; }
.tutor-form { padding-top: 14px; border-top: 1px solid var(--line); }
.tutor-form label { display: block; margin-bottom: 7px; color: var(--muted); font-size: 11px; font-weight: 650; }
.tutor-form textarea { width: 100%; resize: none; padding: 12px; border: 1px solid var(--line); border-radius: 14px; outline: 0; background: white; }
.tutor-form textarea:focus { border-color: var(--blue); box-shadow: 0 0 0 3px rgba(0,113,227,.12); }
.tutor-form-actions { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-top: 8px; }
.tutor-form-actions span { color: var(--muted); font-size: 10px; }
body.tutor-open { overflow: hidden; }

@media (max-width: 1050px) {
  .stat-grid { grid-template-columns: repeat(2, 1fr); }
  .teach-layout { display: block; }
  .slide-browser { display: none; }
  .study-split { grid-template-columns: minmax(320px, .9fr) minmax(350px, 1.1fr); }
  .mode-grid { grid-template-columns: repeat(2, 1fr); }
  .custom-practice { grid-template-columns: 1fr; }
  .custom-controls { grid-template-columns: 1fr 1fr; }
  .library-layout { grid-template-columns: 1fr; }
  .upload-card { position: static; }
}

@media (max-width: 780px) {
  .sidebar { display: none; }
  .main { margin-left: 0; padding: 26px 16px 104px; }
  .mobile-nav {
    position: fixed;
    inset: auto 10px 10px;
    z-index: 40;
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    padding: 7px;
    border: 1px solid rgba(0,0,0,.08);
    border-radius: 19px;
    background: rgba(250,250,252,.88);
    box-shadow: 0 13px 40px rgba(0,0,0,.15);
    backdrop-filter: blur(25px);
  }
  .mobile-nav .nav-button { min-width: 0; display: grid; justify-items: center; gap: 2px; padding: 7px 1px; font-size: 8px; line-height: 1.05; text-align: center; }
  .mobile-nav .nav-button svg { width: 19px; height: 19px; }
  .hero { min-height: auto; grid-template-columns: 1fr; }
  .preparedness { display: none; }
  .section-grid { grid-template-columns: 1fr; }
  .teach-layout { display: block; }
  .slide-browser { display: none; }
  .teach-toolbar { display: none; }
  .study-split { display: block; }
  .slide-column { display: none; }
  .mobile-study-tools {
    position: sticky;
    top: 0;
    z-index: 25;
    display: grid;
    gap: 8px;
    margin: 0 -4px 14px;
    padding: 5px 4px 9px;
    background: linear-gradient(to bottom, rgba(245,245,247,.98) 88%, rgba(245,245,247,0));
  }
  .mobile-slide-nav {
    display: grid;
    grid-template-columns: 44px minmax(0, 1fr) 44px;
    align-items: stretch;
    gap: 7px;
  }
  .mobile-slide-step {
    border: 1px solid var(--line);
    border-radius: 13px;
    color: var(--blue);
    background: rgba(255,255,255,.95);
    box-shadow: 0 5px 18px rgba(0,0,0,.06);
    font-size: 29px;
    cursor: pointer;
  }
  .mobile-slide-step:disabled { color: #aaaab0; opacity: .55; }
  .mobile-slide-picker {
    min-width: 0;
    display: grid;
    gap: 2px;
    padding: 6px 10px;
    border: 1px solid var(--line);
    border-radius: 13px;
    background: rgba(255,255,255,.95);
    box-shadow: 0 5px 18px rgba(0,0,0,.06);
  }
  .mobile-slide-picker span { color: var(--muted); font-size: 9px; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; }
  .mobile-slide-picker select {
    min-width: 0;
    width: 100%;
    border: 0;
    outline: 0;
    color: var(--ink);
    background: transparent;
    font-size: 13px;
    font-weight: 650;
  }
  .mobile-source-summary {
    min-height: 142px;
    display: grid;
    grid-template-columns: minmax(125px, 43%) minmax(0, 1fr);
    gap: 11px;
    padding: 9px;
    border-radius: 17px;
    background: rgba(255,255,255,.96);
    box-shadow: 0 8px 26px rgba(0,0,0,.08);
  }
  .mobile-slide-preview {
    position: relative;
    overflow: hidden;
    min-width: 0;
    padding: 0;
    border: 0;
    border-radius: 11px;
    background: #ddd;
    cursor: zoom-in;
  }
  .mobile-slide-preview img { width: 100%; height: 100%; display: block; object-fit: contain; }
  .mobile-slide-preview > span {
    position: absolute;
    inset: auto 6px 6px;
    padding: 4px 6px;
    border-radius: 7px;
    color: white;
    background: rgba(0,0,0,.64);
    font-size: 9px;
    font-weight: 650;
  }
  .mobile-big-picture { min-width: 0; align-self: center; }
  .mobile-big-picture > span { display: block; margin-bottom: 3px; color: var(--blue); font-size: 9px; font-weight: 750; text-transform: uppercase; }
  .mobile-big-picture strong { display: block; overflow: hidden; margin-bottom: 5px; font-size: 14px; line-height: 1.15; text-overflow: ellipsis; white-space: nowrap; }
  .mobile-big-picture p {
    display: -webkit-box;
    overflow: hidden;
    margin: 0;
    color: #4e4e53;
    font-size: 11px;
    line-height: 1.35;
    -webkit-box-orient: vertical;
    -webkit-line-clamp: 6;
  }
  .desktop-slide-frame, .desktop-big-picture { display: none; }
  .slide-column { position: static; }
  .slide-note-editor { margin: 12px 0; }
  .lecture-notes-grid { grid-template-columns: 1fr; }
  .mode-grid { grid-template-columns: 1fr; }
  .mode-card { min-height: 116px; flex-direction: row; gap: 14px; padding: 17px; }
  .mode-card h3 { margin-top: 0; }
  .mode-card.compact { min-height: 76px; }
  .custom-controls { grid-template-columns: 1fr; }
  .summary-grid { grid-template-columns: 1fr 1fr; }
  .analytics-grid .wide, .analytics-grid .narrow { grid-column: 1 / -1; }
  .top-row { align-items: flex-start; flex-direction: column; }
  .top-row { gap: 14px; margin-bottom: 24px; }
  .page-title { font-size: clamp(32px, 9vw, 36px); }
  .page-subtitle { font-size: 15px; }
  .lesson-head { flex-direction: column; padding-top: 6px; }
  .lesson-head .source-badge { display: none; }
  .ask-clarity-fab { right: 16px; bottom: 86px; min-width: 46px; padding: 6px; }
  .ask-clarity-fab span { display: none; }
  .tutor-panel { inset: max(12px, env(safe-area-inset-top)) 8px 8px; width: auto; border-radius: 24px; }
  .lecture-grid { grid-template-columns: 1fr; }
  .lecture-open, .lecture-card { min-height: 166px; }
  .library-layout { gap: 14px; }
  .session-header { grid-template-columns: 1fr auto 1fr; gap: 7px; }
  .back-button, .flag-button { min-height: 38px; padding: 0 10px; font-size: 12px; }
  .session-count strong { font-size: 13px; }
  .flashcard-controls { grid-template-columns: 1fr; }
  .flashcard-controls .control-button { justify-self: start; grid-row: 2; }
  .rating-actions { width: 100%; grid-template-columns: 1fr 1fr; }
  .rating-actions .button { min-width: 0; }
  .flashcard-controls > .button { width: 100%; }
}

@media (max-width: 480px) {
  .stat-grid { grid-template-columns: 1fr 1fr; gap: 9px; }
  .stat-card { padding: 15px; }
  .stat-card strong { font-size: 24px; }
  .hero { padding: 28px 23px; border-radius: 27px; }
  .panel, .lesson-block, .question-card { border-radius: 20px; }
  .flashcard { min-height: 340px; padding: 30px 22px; }
  .flashcard h2 { font-size: 25px; }
  .back-button span, .flag-button span { display: none; }
  .lesson-block { padding: 20px; }
  .lesson-block p, .lesson-block li { font-size: 14px; line-height: 1.55; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
}