@import url('https://fonts.googleapis.com/css2?family=Outfit:wght@300;400;500;600;700;800;900&display=swap');

:root {
  --bg: #09090b;
  --surface: rgba(24, 24, 27, 0.6);
  --surface-hover: rgba(39, 39, 42, 0.8);
  --surface-soft: rgba(24, 24, 27, 0.4);
  --ink: #f4f4f5;
  --muted: #a1a1aa;
  --line: rgba(255, 255, 255, 0.1);
  --line-strong: rgba(255, 255, 255, 0.2);
  
  --teal: #2dd4bf;
  --teal-dark: #14b8a6;
  --rose: #f43f5e;
  --amber: #fbbf24;
  --blue: #3b82f6;
  --purple: #8b5cf6;
  
  --primary: #2dd4bf;
  --primary-glow: rgba(45, 212, 191, 0.4);
  
  --shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
  --radius: 12px;
  
  font-family: 'Outfit', system-ui, -apple-system, sans-serif;
  color: var(--ink);
  background: var(--bg);
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 320px;
  background: var(--bg);
  background-image: 
    radial-gradient(circle at 15% 50%, rgba(45, 212, 191, 0.05), transparent 25%),
    radial-gradient(circle at 85% 30%, rgba(139, 92, 246, 0.05), transparent 25%);
  background-attachment: fixed;
}

button, input, select {
  font: inherit;
}

button, select, input[type="search"] {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

button {
  min-height: 42px;
  padding: 0 16px;
  cursor: pointer;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  font-weight: 500;
}

button:hover {
  border-color: var(--line-strong);
  background: var(--surface-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
}

button:focus-visible, select:focus-visible, input:focus-visible, a:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.primary-button {
  border-color: transparent;
  background: linear-gradient(135deg, var(--teal), var(--blue));
  color: #fff;
  font-weight: 600;
  box-shadow: 0 4px 15px var(--primary-glow);
}
.primary-button:hover {
  box-shadow: 0 6px 20px var(--primary-glow);
  transform: translateY(-2px) scale(1.02);
}

.back-to-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 100;
  display: inline-grid;
  place-items: center;
  width: 52px;
  height: 52px;
  min-height: 52px;
  padding: 0;
  border-radius: 50%;
  border-color: rgba(45, 212, 191, 0.35);
  background: linear-gradient(135deg, rgba(45, 212, 191, 0.95), rgba(59, 130, 246, 0.9));
  color: #020617;
  font-size: 1.55rem;
  font-weight: 900;
  box-shadow: 0 14px 34px rgba(0,0,0,0.38), 0 0 22px rgba(45, 212, 191, 0.24);
  opacity: 0;
  pointer-events: none;
  transform: translateY(14px) scale(0.92);
}

.back-to-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0) scale(1);
}

.back-to-top:hover {
  background: linear-gradient(135deg, var(--teal), var(--blue));
  color: #020617;
  transform: translateY(-3px) scale(1.04);
}

/* Top Band & Header */
.top-band {
  color: #fff;
  background: transparent;
  position: relative;
  overflow: hidden;
}

.top-band::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  background: linear-gradient(135deg, rgba(45, 212, 191, 0.1) 0%, rgba(139, 92, 246, 0.1) 100%);
  z-index: -1;
  backdrop-filter: blur(20px);
}

.topbar {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  padding: 24px 0 0;
}

.topbar a {
  color: var(--ink);
  text-decoration: none;
  border: 1px solid var(--line);
  border-radius: 99px;
  padding: 8px 16px;
  font-size: 0.9rem;
  font-weight: 500;
  background: var(--surface);
  backdrop-filter: blur(10px);
  transition: all 0.3s ease;
}

.topbar a:hover {
  background: var(--surface-hover);
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-2px);
}

.hero-grid {
  width: min(1180px, calc(100% - 32px));
  min-height: 480px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(0, 1.1fr) minmax(320px, 0.9fr);
  gap: 60px;
  align-items: center;
  padding: 60px 0 80px;
}

.hero-copy {
  max-width: 760px;
}

.eyebrow {
  margin: 0 0 16px;
  background: linear-gradient(135deg, var(--teal), var(--blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-size: 0.85rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 1.5px;
}

h1, h2, h3, h4 {
  margin: 0;
  line-height: 1.1;
  font-weight: 700;
  letter-spacing: -0.02em;
}

h1 {
  font-size: clamp(3rem, 6vw, 4.5rem);
  font-weight: 800;
  background: linear-gradient(to right, #fff, #a1a1aa);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 24px;
}

h2 {
  font-size: clamp(2rem, 4vw, 2.8rem);
  margin-bottom: 16px;
}

h3 {
  font-size: 1.25rem;
}

.lead {
  max-width: 600px;
  color: var(--muted);
  font-size: 1.15rem;
  line-height: 1.6;
  margin-bottom: 32px;
}

/* Stats */
.exam-stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
  width: min(560px, 100%);
  margin: 40px 0 0;
}

.exam-stats div {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 20px;
  background: linear-gradient(145deg, var(--surface), rgba(0,0,0,0.2));
  backdrop-filter: blur(10px);
  border-top-color: rgba(255,255,255,0.15);
  border-left-color: rgba(255,255,255,0.15);
  box-shadow: 0 8px 32px rgba(0,0,0,0.2);
  transition: transform 0.3s ease;
}
.exam-stats div:hover {
  transform: translateY(-5px);
  border-color: var(--primary);
}

.exam-stats dt {
  color: var(--muted);
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.exam-stats dd {
  margin: 8px 0 0;
  font-size: 1.8rem;
  font-weight: 800;
  color: #fff;
  background: linear-gradient(135deg, #fff, var(--teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

/* Geometry Strip */
.geometry-strip {
  margin: 0;
  min-height: 270px;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: linear-gradient(135deg, rgba(255,255,255,0.03), rgba(255,255,255,0.01));
  box-shadow: inset 0 0 0 1px rgba(255,255,255,0.05), 0 20px 40px rgba(0,0,0,0.4);
  backdrop-filter: blur(20px);
  overflow: hidden;
  position: relative;
}
.geometry-strip::before {
  content: '';
  position: absolute;
  top: -50%; left: -50%; width: 200%; height: 200%;
  background: conic-gradient(from 0deg at 50% 50%, transparent 0%, var(--primary-glow) 50%, transparent 100%);
  animation: rotate 10s linear infinite;
  opacity: 0.3;
}
@keyframes rotate {
  100% { transform: rotate(360deg); }
}

.geometry-strip svg {
  width: 100%;
  height: 100%;
  min-height: 270px;
  color: #fff;
  position: relative;
  z-index: 1;
}

.diagram line,
.diagram polyline,
.diagram circle,
.diagram path {
  stroke: rgba(255, 255, 255, 0.72);
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-linejoin: round;
  fill: none;
}

.diagram polygon {
  stroke: rgba(255, 255, 255, 0.82);
  stroke-width: 2.4;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.diagram .axis {
  stroke: var(--amber);
  stroke-width: 2.8;
  opacity: 0.8;
}

.diagram .radius {
  stroke: rgba(255, 255, 255, 0.58);
}

.diagram .orbit {
  stroke: rgba(255, 255, 255, 0.84);
  stroke-width: 2.6;
}

.diagram .vector {
  stroke-width: 3.1;
}

.diagram .vector-teal {
  stroke: var(--teal);
  marker-end: url(#arrowTeal);
}

.diagram .vector-amber {
  stroke: var(--amber);
  marker-end: url(#arrowAmber);
}

.diagram .vector-rose {
  stroke: var(--rose);
  marker-end: url(#arrowRose);
}

.diagram .arc-arrow {
  stroke: var(--amber);
  stroke-width: 3;
  marker-end: url(#arrowAmber);
}

.diagram .normal {
  stroke-width: 3;
}

.diagram .dash {
  stroke: rgba(255, 255, 255, 0.52);
  stroke-width: 2;
  stroke-dasharray: 5 7;
  opacity: 1;
}

#arrowTeal path {
  fill: #14b8a6;
  stroke: none;
}

#arrowAmber path {
  fill: #f59e0b;
  stroke: none;
}

#arrowRose path {
  fill: #fb7185;
  stroke: none !important;
}

.diagram text {
  fill: rgba(255, 255, 255, 0.9);
  font-size: 12px;
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  stroke: none;
  letter-spacing: 0;
}

.diagram .mini-title {
  fill: var(--teal);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0;
}

.diagram .label.muted {
  fill: rgba(255, 255, 255, 0.7);
  font-size: 11px;
  font-weight: 600;
}

/* Controls Band */
.controls-band {
  position: sticky;
  top: 20px;
  z-index: 50;
  display: grid;
  grid-template-columns: repeat(6, minmax(130px, 1fr));
  gap: 16px;
  align-items: end;
  width: min(1180px, calc(100% - 32px));
  margin: -40px auto 40px;
  border: 1px solid var(--line);
  border-radius: 20px;
  padding: 20px;
  background: rgba(24, 24, 27, 0.75);
  box-shadow: 0 10px 40px rgba(0,0,0,0.5);
  backdrop-filter: blur(24px);
  -webkit-backdrop-filter: blur(24px);
}

.mode-dashboard {
  width: min(1180px, 100%);
  margin: -20px auto 30px;
  border: 1px solid var(--line);
  border-radius: 20px;
  padding: 24px;
  background: linear-gradient(to bottom, rgba(39,39,42,0.5), rgba(24,24,27,0.5));
  backdrop-filter: blur(12px);
  box-shadow: var(--shadow);
}

.mode-intro {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 24px;
  margin-bottom: 24px;
}

.mode-intro p:last-child {
  max-width: 520px;
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.mode-switch {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}

.mode-switch button {
  min-height: 100px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: flex-start;
  gap: 8px;
  padding: 20px;
  text-align: left;
  border-radius: 16px;
  background: var(--surface);
  border: 1px solid var(--line);
  position: relative;
  overflow: hidden;
}

.mode-switch button::before {
  content: '';
  position: absolute;
  top: 0; left: 0; width: 100%; height: 100%;
  background: linear-gradient(135deg, transparent, rgba(255,255,255,0.05));
  opacity: 0;
  transition: opacity 0.3s;
}

.mode-switch button:hover::before {
  opacity: 1;
}

.mode-switch button[aria-pressed="true"] {
  border-color: var(--primary);
  background: rgba(45, 212, 191, 0.1);
  box-shadow: inset 0 0 0 1px var(--primary), 0 0 20px var(--primary-glow);
}

.mode-switch span {
  font-weight: 700;
  font-size: 1.1rem;
  color: #fff;
}

.mode-switch small {
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.4;
}

/* Controls inside band */
.small-label, .control-group label, .subject-control .small-label {
  display: block;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.progress-panel { display: grid; gap: 8px; }
.progress-panel strong { display: block; font-size: 1.1rem; }
.progress-track {
  height: 8px;
  overflow: hidden;
  border-radius: 99px;
  background: rgba(255,255,255,0.1);
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.3);
}
.progress-track span {
  display: block;
  width: 0%; height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--teal), var(--purple));
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  box-shadow: 0 0 10px var(--primary-glow);
}

.control-group { display: grid; gap: 6px; }

.subject-switch {
  display: grid;
  grid-template-columns: 1fr 1fr;
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 4px;
  background: rgba(0,0,0,0.3);
}
.subject-switch button {
  min-height: 34px;
  border: 0;
  background: transparent;
  color: var(--muted);
  border-radius: 8px;
}
.subject-switch button[aria-pressed="true"] {
  background: var(--surface-hover);
  color: #fff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

select, input[type="search"] {
  min-height: 42px;
  padding: 0 16px;
  width: 100%;
  appearance: none;
  background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23a1a1aa' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
  background-repeat: no-repeat;
  background-position: right 12px center;
  background-size: 16px;
}
input[type="search"] {
  background-image: none;
}

.check-control {
  min-height: 42px;
  display: inline-flex;
  align-items: center;
  gap: 12px;
  padding: 0 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}
.check-control:hover {
  background: var(--surface-hover);
}
.check-control input {
  width: 18px; height: 18px;
  accent-color: var(--teal);
  cursor: pointer;
}

.button-row {
  display: flex; flex-wrap: wrap; gap: 12px;
  justify-content: flex-end;
  grid-column: span 2;
}

main {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto 80px;
}

.content-section {
  scroll-margin-top: 140px;
  margin-bottom: 60px;
}

body[data-mode="study"] #simulado, body[data-mode="study"] #gabarito { display: none; }
body[data-mode="solve"] #estudar { display: none; }
body[data-mode="review"] #estudar { display: none; }

.section-heading {
  display: flex; align-items: end; justify-content: space-between;
  gap: 24px; margin-bottom: 32px;
}
.section-heading p:last-child {
  max-width: 520px; margin: 0; color: var(--muted); line-height: 1.6;
}

/* Question Cards & Lists */
.question-list, .solution-list { display: grid; gap: 20px; }

.question-card, .solution-card, .formula-grid article {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
  transition: transform 0.3s ease, border-color 0.3s ease;
}
.question-card:hover, .formula-grid article:hover {
  transform: translateY(-4px);
  border-color: var(--line-strong);
}

.question-card {
  display: grid;
  grid-template-columns: 70px minmax(0, 1fr);
  overflow: hidden;
}

.question-card.wrong-question {
  border-color: rgba(244, 63, 94, 0.45);
  box-shadow: 0 4px 24px rgba(244, 63, 94, 0.12);
}

.question-status {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  justify-content: flex-start;
  padding-top: 24px;
  background: rgba(255,255,255,0.02);
  border-right: 1px solid var(--line);
}
.question-status input {
  width: 24px; height: 24px;
  accent-color: var(--teal);
  cursor: pointer;
}
.status-check {
  display: grid;
  justify-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
}
.status-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 48px;
  border-radius: 999px;
  padding: 6px 10px;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
}
.status-pill.wrong {
  border: 1px solid rgba(244, 63, 94, 0.45);
  background: rgba(244, 63, 94, 0.14);
  color: #fecdd3;
}

.question-body { min-width: 0; padding: 24px; }

.question-meta, .solution-meta {
  display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 16px;
}

.badge {
  display: inline-flex; align-items: center;
  min-height: 28px; border-radius: 99px;
  padding: 0 12px;
  font-size: 0.75rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.5px;
  background: rgba(255,255,255,0.1);
  color: var(--ink);
  border: 1px solid rgba(255,255,255,0.05);
}
.badge.easy { background: rgba(45, 212, 191, 0.15); color: #5eead4; border-color: rgba(45, 212, 191, 0.3); }
.badge.medium { background: rgba(251, 191, 36, 0.15); color: #fcd34d; border-color: rgba(251, 191, 36, 0.3); }
.badge.hard { background: rgba(244, 63, 94, 0.15); color: #fda4af; border-color: rgba(244, 63, 94, 0.3); }
.badge.common { background: rgba(59, 130, 246, 0.15); color: #93c5fd; border-color: rgba(59, 130, 246, 0.3); }
.badge.review { background: rgba(139, 92, 246, 0.15); color: #c4b5fd; border-color: rgba(139, 92, 246, 0.3); }
.badge.wrong { background: rgba(244, 63, 94, 0.14); color: #fecdd3; border-color: rgba(244, 63, 94, 0.36); }

.question-title {
  display: flex; flex-wrap: wrap; gap: 12px; align-items: baseline;
  margin-bottom: 16px;
}
.question-title span { color: var(--teal); font-size: 0.95rem; font-weight: 700; }

.question-learning {
  display: grid; gap: 8px; margin-bottom: 16px;
  border: 1px solid rgba(45, 212, 191, 0.2);
  border-radius: var(--radius); padding: 16px;
  background: rgba(45, 212, 191, 0.05);
}
.question-learning p { margin: 0; color: #ccfbf1; line-height: 1.6; }

.question-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 24px; }
.question-actions .marked-review {
  border-color: rgba(251, 191, 36, 0.5);
  background: rgba(251, 191, 36, 0.1);
  color: #fcd34d;
}
.question-actions .marked-wrong {
  border-color: rgba(244, 63, 94, 0.55);
  background: rgba(244, 63, 94, 0.12);
  color: #fecdd3;
}

.hint-panel {
  margin-top: 16px;
  border: 1px solid rgba(251, 191, 36, 0.3);
  border-radius: var(--radius); padding: 16px;
  background: rgba(251, 191, 36, 0.05);
}
.hint-panel p { margin: 8px 0 0; color: #fef3c7; line-height: 1.6; }

.prompt { margin: 0; color: var(--ink); line-height: 1.7; font-size: 1.05rem; }

.parts, .steps { margin: 16px 0 0; padding-left: 1.5rem; line-height: 1.7; }
.parts li, .steps li { padding-left: 8px; margin-bottom: 10px; }

.math-line { display: block; margin: 12px 0; color: var(--blue); font-weight: 600; font-family: monospace; font-size: 1.1rem; }

/* Study Guide */
.study-guide {
  display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 20px;
}
.study-card {
  border: 1px solid var(--line); border-radius: var(--radius); padding: 24px;
  background: var(--surface); box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}
.study-card h3 { margin-bottom: 12px; color: #fff; }
.study-card p { margin: 10px 0 0; color: var(--muted); line-height: 1.6; }
.wide-study-card { grid-column: span 2; background: rgba(45, 212, 191, 0.05); border-color: rgba(45, 212, 191, 0.2); }
.lesson-card { border-left: 4px solid var(--teal); }
.formula-study-card { border-top: 4px solid var(--purple); }
.method-study-card { grid-row: span 2; }
.example-study-card { grid-column: span 2; background: rgba(59, 130, 246, 0.05); border-color: rgba(59, 130, 246, 0.2); }
.mistake-study-card { background: rgba(244, 63, 94, 0.05); border-color: rgba(244, 63, 94, 0.2); }

.formula-list, .deep-steps { margin: 16px 0 0; padding-left: 1.2rem; color: var(--muted); line-height: 1.7; }
.formula-list li, .deep-steps li { margin-bottom: 12px; padding-left: 4px; }
.formula-list strong { color: var(--primary); }
.formula-list span { display: block; margin-top: 4px; color: #fff; font-weight: 600; font-family: monospace; }
.formula-list small { display: block; margin-top: 4px; color: var(--muted); }
.deep-steps li::marker { color: var(--teal); font-weight: 900; }

/* Formulas */
.formula-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 20px; }
.formula-grid article { padding: 24px; border-top: 4px solid var(--teal); background: var(--surface); }
.formula-grid article:nth-child(2n) { border-top-color: var(--blue); }
.formula-grid article:nth-child(3n) { border-top-color: var(--purple); }
.formula-grid h3 { margin-bottom: 16px; }
.formula-grid p { margin: 10px 0 0; color: var(--muted); line-height: 1.6; }
.formula-grid .formula-easy {
  border: 1px solid rgba(45, 212, 191, 0.18);
  border-radius: 12px;
  padding: 12px;
  background: rgba(45, 212, 191, 0.06);
  color: #ccfbf1;
}
/* Solutions */
.solution-gate {
  border: 2px dashed rgba(255,255,255,0.2); border-radius: 20px; padding: 40px;
  background: rgba(255,255,255,0.02); text-align: center;
}
.answer-picker {
  display: grid; grid-template-columns: minmax(220px, 340px) auto auto; gap: 12px; align-items: end;
  margin-bottom: 24px; border: 1px solid var(--line); border-radius: var(--radius); padding: 20px;
  background: var(--surface); box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}
.solution-gate h3 { margin-bottom: 12px; font-size: 1.5rem; }
.solution-gate p { max-width: 680px; margin: 0 auto; color: var(--muted); line-height: 1.6; }

.solution-card { padding: 0; border-left: 0; overflow: hidden; }
.solution-header {
  display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 20px; align-items: start;
  padding: 30px; border-bottom: 1px solid var(--line);
  background: linear-gradient(135deg, rgba(255,255,255,0.05), transparent);
}
.solution-header h3 { margin-top: 12px; font-size: clamp(1.4rem, 2.5vw, 2rem); }
.solution-nav { display: flex; flex-wrap: wrap; gap: 10px; justify-content: flex-end; }
.solution-nav button:disabled { cursor: not-allowed; opacity: 0.3; transform: none; }

.solution-lesson { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; padding: 24px 30px 10px; }
.teacher-card { border: 1px solid rgba(255,255,255,0.1); border-radius: var(--radius); padding: 20px; background: rgba(0,0,0,0.2); }
.main-teacher-card { border-color: rgba(45, 212, 191, 0.3); background: rgba(45, 212, 191, 0.05); }
.wide-teacher-card { grid-column: 1 / -1; }
.teacher-kicker { display: inline-flex; margin-bottom: 10px; color: var(--teal); font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 1px;}
.teacher-card h4, .step-section-title h4 { margin: 0; font-size: 1.1rem; }
.teacher-card p { margin: 10px 0 0; color: var(--muted); line-height: 1.6; }
.concept-list, .mini-steps { margin: 12px 0 0; padding-left: 1.2rem; color: var(--muted); line-height: 1.6; }
.concept-list li, .mini-steps li { margin-bottom: 8px; padding-left: 4px; }
.mini-steps strong { color: var(--primary); }

.formula-notebook {
  grid-column: 1 / -1;
  border: 1px solid rgba(45, 212, 191, 0.24);
  border-radius: var(--radius);
  padding: 24px;
  background: linear-gradient(135deg, rgba(45, 212, 191, 0.08), rgba(59, 130, 246, 0.05));
}
.formula-notebook h4 { margin: 0; font-size: 1.2rem; }
.formula-intro { max-width: 880px; margin: 10px 0 0; color: #ccfbf1; line-height: 1.6; }
.formula-book-list { display: grid; gap: 12px; margin-top: 20px; }
.formula-row {
  display: grid;
  grid-template-columns: minmax(150px, 0.85fr) minmax(220px, 1.25fr) minmax(180px, 1fr);
  gap: 16px;
  align-items: center;
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 12px;
  padding: 16px;
  background: rgba(0,0,0,0.22);
}
.formula-row strong { display: block; margin-top: 4px; color: #fff; }
.formula-main { display: grid; gap: 8px; }
.formula-topic {
  display: inline-flex;
  color: var(--teal);
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
}
.formula-equation {
  margin: 0;
  color: #fff;
  font-family: Georgia, 'Times New Roman', serif;
  font-size: clamp(1rem, 1.5vw, 1.25rem);
  line-height: 1.45;
  overflow-wrap: anywhere;
}
.formula-row .formula-easy {
  margin: 0;
  border-radius: 10px;
  padding: 10px 12px;
  background: rgba(45, 212, 191, 0.08);
  color: #ccfbf1;
  line-height: 1.5;
}
.formula-note { margin: 0; color: var(--muted); line-height: 1.5; }
.formula-detail-columns {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
  margin-top: 20px;
}
.formula-detail-columns > div {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 16px;
}
.formula-detail-columns h5 { margin: 0; color: #fff; font-size: 1rem; }

.step-section-title { padding: 30px 30px 0; }
.step-timeline { display: grid; gap: 16px; margin: 20px 0 0; padding: 0 30px 30px; list-style: none; counter-reset: solution-step; }
.step-card {
  display: grid; grid-template-columns: 80px minmax(0, 1fr); gap: 20px;
  border: 1px solid rgba(255,255,255,0.1); border-radius: var(--radius); padding: 20px; background: rgba(255,255,255,0.02);
}
.step-marker { display: grid; align-content: start; justify-items: center; gap: 8px; border-right: 1px solid var(--line); padding-right: 20px; }
.step-marker span { width: 40px; height: 40px; display: inline-grid; place-items: center; border-radius: 50%; background: var(--teal); color: #000; font-weight: 800; font-size: 1.2rem; }
.step-marker small { color: var(--teal); font-size: 0.75rem; font-weight: 700; text-transform: uppercase; }
.step-card p { margin: 0; color: var(--ink); line-height: 1.7; }
.step-content { min-width: 0; display: grid; gap: 14px; }
.step-formula-box {
  display: grid;
  gap: 10px;
  border: 1px solid rgba(45, 212, 191, 0.24);
  border-radius: 14px;
  padding: 14px;
  background: rgba(45, 212, 191, 0.06);
}
.step-formula-box > span {
  color: var(--teal);
  font-size: 0.74rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 0;
}
.step-formula-line {
  display: grid;
  grid-template-columns: minmax(120px, 0.65fr) minmax(180px, 1fr);
  gap: 8px 14px;
  align-items: center;
}
.step-formula-line strong {
  color: #fff;
  font-size: 0.92rem;
}
.step-formula-line code {
  display: block;
  width: 100%;
  border-radius: 10px;
  padding: 10px 12px;
  background: rgba(0,0,0,0.32);
  color: #fef3c7;
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1rem;
  line-height: 1.45;
  white-space: normal;
  overflow-wrap: anywhere;
}
.step-easy {
  margin: 0 0 8px;
  color: #ccfbf1;
  line-height: 1.5;
}
.step-formula-line small {
  grid-column: 2;
  color: var(--muted);
  line-height: 1.45;
}

.answer-banner { margin: 0 30px 24px; border-radius: var(--radius); padding: 24px; background: linear-gradient(135deg, rgba(45, 212, 191, 0.2), rgba(59, 130, 246, 0.2)); border: 1px solid rgba(45, 212, 191, 0.3); color: #fff; }
.answer-banner span { display: block; margin-bottom: 8px; color: var(--teal); font-size: 0.8rem; font-weight: 700; text-transform: uppercase; letter-spacing: 1px;}
.answer-banner p { margin: 0; font-size: 1.2rem; font-weight: 700; line-height: 1.6; }

.solution-footer-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; padding: 0 30px 30px; }
.check-card { background: rgba(59, 130, 246, 0.05); border-color: rgba(59, 130, 246, 0.2); }
.mistake-card { background: rgba(244, 63, 94, 0.05); border-color: rgba(244, 63, 94, 0.2); }

.empty-state { border: 2px dashed rgba(255,255,255,0.1); border-radius: 20px; padding: 40px; background: rgba(0,0,0,0.2); color: var(--muted); text-align: center; font-size: 1.1rem; }

.page-footer { border-top: 1px solid var(--line); padding: 40px 20px; color: var(--muted); text-align: center; }
.page-footer p { margin: 0; font-size: 1rem; }

@media (max-width: 980px) {
  .hero-grid { grid-template-columns: 1fr; min-height: auto; text-align: center; }
  .hero-copy { margin: 0 auto; }
  .exam-stats { margin: 40px auto 0; }
  .geometry-strip { min-height: 240px; }
  .controls-band { position: static; grid-template-columns: repeat(2, minmax(0, 1fr)); margin-top: -20px; }
  .mode-intro { display: block; text-align: center; }
  .mode-intro p:last-child { margin: 12px auto 0; }
  .mode-switch, .study-guide { grid-template-columns: 1fr; }
  .wide-study-card, .example-study-card { grid-column: auto; }
  .progress-panel, .subject-control, .search-control, .button-row { grid-column: 1 / -1; }
  .button-row { justify-content: center; }
  .formula-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .formula-row { grid-template-columns: 1fr; align-items: start; }
  .formula-detail-columns { grid-template-columns: 1fr; }
  .answer-picker { grid-template-columns: 1fr; }
  .solution-header, .solution-lesson, .solution-footer-grid { grid-template-columns: 1fr; }
  .solution-nav { justify-content: flex-start; }
}

@media (max-width: 680px) {
  .topbar { justify-content: center; flex-wrap: wrap; }
  .hero-grid, main, .controls-band, .topbar, .mode-dashboard { width: min(100% - 32px, 1180px); }
  .exam-stats, .controls-band, .formula-grid { grid-template-columns: 1fr; }
  .section-heading { display: block; text-align: center; }
  .section-heading p:last-child { margin: 12px auto 0; }
  .question-card { grid-template-columns: 1fr; }
  .question-status {
    flex-direction: row;
    align-items: center;
    justify-content: flex-start;
    padding: 16px 24px;
    border-right: none;
    border-bottom: 1px solid var(--line);
  }
  .status-check { grid-template-columns: auto auto; align-items: center; justify-items: start; }
  .question-body, .solution-card { padding: 20px; }
  .solution-card { padding: 0; }
  .solution-header, .solution-lesson, .step-section-title, .step-timeline, .solution-footer-grid { padding-left: 20px; padding-right: 20px; }
  .step-card { grid-template-columns: 1fr; gap: 12px; }
  .step-marker { grid-template-columns: auto 1fr; justify-items: start; align-items: center; border-right: 0; border-bottom: 1px solid var(--line); padding-right: 0; padding-bottom: 12px; }
  .step-formula-line { grid-template-columns: 1fr; }
  .step-formula-line small { grid-column: auto; }
  .answer-banner { margin-left: 20px; margin-right: 20px; }
  .question-actions button, .button-row button { flex: 1 1 100%; }
  .back-to-top { right: 16px; bottom: 16px; width: 46px; height: 46px; min-height: 46px; }
}

@media print {
  body { background: #fff; color: #000; }
  .topbar, .controls-band, .answer-picker, .geometry-strip, .page-footer, .solution-gate { display: none !important; }
  .top-band { color: #000; background: #fff; }
  .hero-grid, main { width: 100%; }
  .hero-grid { min-height: auto; padding: 0 0 20px; display: block; }
  .lead, .section-heading p:last-child, .prompt, .formula-grid p, .exam-stats dd { color: #000; }
  .question-card, .solution-card, .formula-grid article { box-shadow: none; break-inside: avoid; border-color: #ccc; }
  .content-section { margin-bottom: 30px; scroll-margin-top: 0; }
  h1 { -webkit-text-fill-color: #000; }
  .exam-stats div { background: #fff; border-color: #ccc; box-shadow: none; }
  .badge { border-color: #ccc; color: #000; }
}