/* Alpha Academy — AI Final Term Prep */
:root {
  --ink: #0f1c24;
  --ink-soft: #243542;
  --slate: #3d5563;
  --mist: #e8eef2;
  --paper: #f7fafb;
  --card: #ffffff;
  --teal: #26b99a;
  --teal-deep: #1a9a7e;
  --teal-soft: #d8f4ec;
  --coral: #e9814d;
  --coral-soft: #fde8e2;
  --gold: #f2c044;
  --ok: #1b7a4e;
  --ok-bg: #e6f5ee;
  --bad: #b42318;
  --bad-bg: #fdeceb;
  --line: #d0dcd8;
  --shadow: 0 12px 40px rgba(15, 28, 36, 0.08);
  --radius: 14px;
  --font-display: "Fraunces", Georgia, serif;
  --font-body: "Outfit", system-ui, sans-serif;
  --max: 1120px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(1200px 600px at 10% -10%, #cfe8e8 0%, transparent 55%),
    radial-gradient(900px 500px at 100% 0%, #f8e4dc 0%, transparent 50%),
    linear-gradient(180deg, #f3f7f8 0%, var(--paper) 40%, #eef4f6 100%);
  min-height: 100vh;
  line-height: 1.65;
}

img,
svg {
  max-width: 100%;
  display: block;
}

a {
  color: var(--teal-deep);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: var(--coral);
}

.skip {
  position: absolute;
  left: -999px;
  top: 0;
}

.skip:focus {
  left: 12px;
  top: 12px;
  z-index: 99;
  background: #fff;
  padding: 8px 12px;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(14px);
  background: rgba(247, 250, 251, 0.88);
  border-bottom: 1px solid rgba(208, 220, 216, 0.8);
}

.header-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0.85rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: inherit;
}

.brand-logo {
  height: 44px;
  width: 44px;
  object-fit: contain;
  display: block;
  border-radius: 10px;
  flex-shrink: 0;
}

.brand-lockup {
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
}

.brand-name {
  font-family: var(--font-display);
  font-weight: 650;
  font-size: 1.05rem;
  letter-spacing: -0.02em;
  color: var(--ink);
  line-height: 1.1;
}

.brand-mark {
  display: none;
}

.brand-text strong {
  display: block;
  font-family: var(--font-display);
  font-size: 1.05rem;
  letter-spacing: -0.02em;
}

.brand-text span {
  display: block;
  font-size: 0.72rem;
  color: var(--slate);
}

.brand-sub {
  display: block;
  font-size: 0.72rem;
  color: var(--slate);
  max-width: 11rem;
  line-height: 1.3;
}

.hero-logo {
  width: min(220px, 55vw);
  height: auto;
  margin: 0 0 1rem;
  animation: rise 0.7s ease both;
}

.footer-logo {
  height: 64px;
  width: auto;
  margin-bottom: 0.75rem;
  background: #fff;
  border-radius: 12px;
  padding: 0.35rem 0.5rem;
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.9rem;
  align-items: center;
}

.nav a {
  text-decoration: none;
  color: var(--ink-soft);
  font-size: 0.92rem;
  font-weight: 500;
  padding: 0.35rem 0.2rem;
}

.nav a.active,
.nav a:hover {
  color: var(--teal);
}

.nav-cta {
  background: var(--ink);
  color: #fff !important;
  padding: 0.45rem 0.9rem !important;
  border-radius: 999px;
}

.nav-toggle {
  display: none;
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 10px;
  padding: 0.4rem 0.65rem;
  cursor: pointer;
}

/* Layout */
.wrap {
  max-width: var(--max);
  margin: 0 auto;
  padding: 1.5rem 1.25rem 4rem;
}

.hero {
  display: grid;
  gap: 1.5rem;
  padding: 2.2rem 0 1rem;
  animation: rise 0.7s ease both;
}

@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(14px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fade-in {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--teal);
}

.hero h1 {
  font-family: var(--font-display);
  font-weight: 650;
  font-size: clamp(2rem, 4.5vw, 3.15rem);
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin: 0.4rem 0 0.75rem;
  max-width: 16ch;
}

.hero .lead {
  font-size: 1.08rem;
  color: var(--slate);
  max-width: 52ch;
  margin: 0 0 1.25rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  border: none;
  border-radius: 999px;
  padding: 0.7rem 1.2rem;
  font-family: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--teal), var(--teal-deep));
  color: #fff;
  box-shadow: 0 10px 24px rgba(13, 115, 119, 0.28);
}

.btn-secondary {
  background: #fff;
  color: var(--ink);
  border: 1px solid var(--line);
}

.btn-ghost {
  background: transparent;
  color: var(--teal-deep);
  border: 1px dashed var(--teal);
}

.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.75rem;
  margin: 1.5rem 0 2rem;
}

.stat {
  background: rgba(255, 255, 255, 0.75);
  border: 1px solid rgba(208, 220, 216, 0.9);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
  animation: rise 0.6s ease both;
}

.stat:nth-child(2) {
  animation-delay: 0.08s;
}
.stat:nth-child(3) {
  animation-delay: 0.16s;
}
.stat:nth-child(4) {
  animation-delay: 0.24s;
}

.stat b {
  display: block;
  font-family: var(--font-display);
  font-size: 1.55rem;
  color: var(--teal-deep);
  line-height: 1.1;
}

.stat span {
  font-size: 0.82rem;
  color: var(--slate);
}

.section-title {
  font-family: var(--font-display);
  font-size: clamp(1.45rem, 2.5vw, 1.9rem);
  letter-spacing: -0.02em;
  margin: 0 0 0.35rem;
}

.section-sub {
  color: var(--slate);
  margin: 0 0 1.25rem;
  max-width: 60ch;
}

.grid-topics {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
}

.topic-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem 1.25rem;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
  transition: transform 0.18s ease, border-color 0.18s ease;
  position: relative;
  overflow: hidden;
}

.topic-card::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 4px;
  background: var(--teal);
}

.topic-card.mid::before {
  background: var(--gold);
}

.topic-card:hover {
  transform: translateY(-3px);
  border-color: #b9cdc8;
}

.topic-card .num {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--teal);
  letter-spacing: 0.04em;
}

.topic-card h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin: 0.35rem 0 0.45rem;
  letter-spacing: -0.02em;
}

.topic-card p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--slate);
}

.badge {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.2rem 0.5rem;
  border-radius: 999px;
  background: var(--teal-soft);
  color: var(--teal-deep);
  margin-top: 0.75rem;
}

.badge.mid {
  background: #f8efd0;
  color: #7a5b00;
}

.pattern-box,
.panel {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.35rem 1.4rem;
  box-shadow: var(--shadow);
  margin: 1.25rem 0;
}

.pattern-box h2 {
  font-family: var(--font-display);
  margin: 0 0 0.75rem;
  font-size: 1.35rem;
}

.pattern-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 0.85rem;
}

.pattern-item {
  background: var(--mist);
  border-radius: 12px;
  padding: 0.9rem 1rem;
}

.pattern-item strong {
  display: block;
  font-size: 0.95rem;
}

.pattern-item span {
  font-size: 0.85rem;
  color: var(--slate);
}

/* Topic page */
.topic-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 1.5rem;
  align-items: start;
}

.toc {
  position: sticky;
  top: 78px;
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem;
}

.toc h4 {
  margin: 0 0 0.6rem;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--slate);
}

.toc a {
  display: block;
  text-decoration: none;
  color: var(--ink-soft);
  font-size: 0.88rem;
  padding: 0.35rem 0;
  border-left: 2px solid transparent;
  padding-left: 0.65rem;
}

.toc a:hover,
.toc a.active {
  color: var(--teal);
  border-left-color: var(--teal);
}

.topic-hero {
  margin-bottom: 1.5rem;
}

.topic-hero h1 {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 3.5vw, 2.5rem);
  letter-spacing: -0.03em;
  margin: 0.3rem 0 0.6rem;
  line-height: 1.2;
}

.lang-tabs {
  display: inline-flex;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.2rem;
  margin: 0.75rem 0 1rem;
}

.lang-tabs button {
  border: none;
  background: transparent;
  border-radius: 999px;
  padding: 0.4rem 0.9rem;
  font-family: inherit;
  font-weight: 600;
  font-size: 0.85rem;
  cursor: pointer;
  color: var(--slate);
}

.lang-tabs button.active {
  background: var(--ink);
  color: #fff;
}

.concept {
  margin: 1.5rem 0;
}

.concept h2 {
  font-family: var(--font-display);
  font-size: 1.4rem;
  margin: 0 0 0.6rem;
  letter-spacing: -0.02em;
}

.concept h3 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  margin: 1.1rem 0 0.4rem;
}

.bilingual {
  display: grid;
  gap: 0.85rem;
}

.en-block,
.rom-block {
  border-radius: 12px;
  padding: 1rem 1.1rem;
}

.en-block {
  background: #fff;
  border: 1px solid var(--line);
}

.rom-block {
  background: linear-gradient(135deg, #eef8f7, #f7fbfb);
  border: 1px solid #c9e0de;
}

.rom-block .label,
.en-block .label {
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-bottom: 0.35rem;
  color: var(--teal);
}

.rom-block .label {
  color: #0a5c5f;
}

.diagram {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.1rem;
  margin: 1rem 0;
  overflow-x: auto;
}

.diagram figcaption {
  font-size: 0.85rem;
  color: var(--slate);
  margin-top: 0.65rem;
  text-align: center;
}

.formula {
  font-family: "Cambria Math", "Times New Roman", serif;
  background: var(--mist);
  border-radius: 10px;
  padding: 0.85rem 1rem;
  margin: 0.75rem 0;
  overflow-x: auto;
  font-size: 1.05rem;
}

.callout {
  border-radius: 12px;
  padding: 0.95rem 1.05rem;
  margin: 1rem 0;
}

.callout.tip {
  background: var(--ok-bg);
  border-left: 4px solid var(--ok);
}

.callout.warn {
  background: var(--coral-soft);
  border-left: 4px solid var(--coral);
}

.callout.exam {
  background: #eef4ff;
  border-left: 4px solid #3b6fd9;
}

.steps {
  counter-reset: step;
  list-style: none;
  padding: 0;
  margin: 0.75rem 0;
}

.steps li {
  counter-increment: step;
  position: relative;
  padding: 0.7rem 0.7rem 0.7rem 3rem;
  margin-bottom: 0.5rem;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 12px;
}

.steps li::before {
  content: counter(step);
  position: absolute;
  left: 0.7rem;
  top: 0.7rem;
  width: 1.7rem;
  height: 1.7rem;
  border-radius: 50%;
  background: var(--teal);
  color: #fff;
  display: grid;
  place-items: center;
  font-size: 0.8rem;
  font-weight: 700;
}

table.data {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  background: #fff;
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid var(--line);
}

table.data th,
table.data td {
  padding: 0.55rem 0.7rem;
  border-bottom: 1px solid var(--line);
  text-align: left;
}

table.data th {
  background: var(--mist);
  font-weight: 650;
}

/* Quiz */
.quiz-box {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-top: 2rem;
  box-shadow: var(--shadow);
}

.quiz-box h2 {
  font-family: var(--font-display);
  margin: 0 0 0.35rem;
}

.quiz-meta {
  color: var(--slate);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.q-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 1rem;
  margin-bottom: 0.85rem;
  background: var(--paper);
}

.q-card.correct {
  border-color: var(--ok);
  background: var(--ok-bg);
}

.q-card.wrong {
  border-color: var(--bad);
  background: var(--bad-bg);
}

.q-card h4 {
  margin: 0 0 0.65rem;
  font-size: 0.98rem;
}

.options {
  display: grid;
  gap: 0.4rem;
}

.options label {
  display: flex;
  gap: 0.55rem;
  align-items: flex-start;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 0.55rem 0.7rem;
  cursor: pointer;
  font-size: 0.92rem;
}

.options label:hover {
  border-color: var(--teal);
}

.options input {
  margin-top: 0.2rem;
}

.feedback {
  margin-top: 0.55rem;
  font-size: 0.88rem;
  display: none;
}

.q-card.correct .feedback,
.q-card.wrong .feedback {
  display: block;
}

.score-banner {
  display: none;
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 12px;
  background: var(--teal-soft);
  font-weight: 650;
}

/* Papers */
.paper-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin: 1rem 0 1.5rem;
}

.paper-nav button {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 999px;
  padding: 0.45rem 0.85rem;
  font-family: inherit;
  font-weight: 600;
  font-size: 0.85rem;
  cursor: pointer;
  min-height: 40px;
}

.paper-nav button.active {
  background: var(--ink);
  color: #fff;
  border-color: var(--ink);
}

.paper {
  background: #fff;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  animation: fade-in 0.35s ease;
  overflow-x: hidden;
  max-width: 100%;
}

.paper-logo {
  height: 72px;
  width: auto;
  margin: 0 auto 0.75rem;
  display: block;
  max-width: 100%;
}

.paper-head {
  text-align: center;
  border-bottom: 2px solid var(--ink);
  padding-bottom: 1rem;
  margin-bottom: 1.25rem;
}

.paper-head h2 {
  font-family: var(--font-display);
  margin: 0.2rem 0;
  font-size: clamp(1.15rem, 3.5vw, 1.55rem);
  line-height: 1.25;
  word-break: break-word;
}

.paper-meta {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem 1rem;
  font-size: 0.88rem;
  color: var(--slate);
}

.paper-meta span {
  background: var(--mist);
  border-radius: 999px;
  padding: 0.25rem 0.65rem;
}

.paper-note {
  margin: 0.75rem 0 0;
  font-size: 0.9rem;
  color: var(--slate);
  text-align: left;
}

.paper-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
  margin-top: 0.75rem;
}

.paper h3 {
  font-family: var(--font-display);
  margin: 1.4rem 0 0.6rem;
  color: var(--teal-deep);
  font-size: clamp(1.05rem, 3vw, 1.25rem);
}

.paper-diagram {
  margin: 0.75rem 0;
}

.paper-diagram svg {
  width: 100%;
  height: auto;
  max-height: 220px;
}

.paper-explain {
  margin: 0.65rem 0 0.85rem;
}

.case-question {
  background: #fff;
  border-radius: 10px;
  padding: 0.75rem;
  border: 1px dashed var(--line);
  font-size: 0.95rem;
  line-height: 1.6;
}

.case-q {
  background: var(--mist);
  border-radius: 12px;
  padding: 1rem;
  margin: 0.75rem 0;
}

.case-q .btn {
  width: auto;
  max-width: 100%;
}

#paper-mcq-form .q-card h4 {
  font-size: 0.95rem;
  line-height: 1.45;
}

#paper-mcq-form .options label {
  min-height: 44px;
  align-items: center;
}

.solution {
  background: var(--ok-bg);
  border: 1px solid #b7dfc8;
  border-radius: 12px;
  padding: 0.9rem 1rem;
  margin: 0.65rem 0 1rem;
}

.solution strong {
  color: var(--ok);
}

.sol-pre {
  white-space: pre-wrap;
  margin: 0.5rem 0 0;
  font-family: var(--font-body);
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--ink-soft);
}

.case-q {
  background: var(--mist);
  border-radius: 12px;
  padding: 1rem;
  margin: 0.75rem 0;
}

.toggle-sol {
  margin: 0.5rem 0 1rem;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  background: var(--ink);
  color: #c9d5dc;
  padding: 2rem 1.25rem;
  margin-top: 2rem;
}

.footer-inner {
  max-width: var(--max);
  margin: 0 auto;
  display: grid;
  gap: 0.5rem;
}

.site-footer a {
  color: #9fd4d4;
}

.site-footer strong {
  color: #fff;
  font-family: var(--font-display);
}

/* Progress */
.progress-bar {
  height: 6px;
  background: var(--mist);
  border-radius: 999px;
  overflow: hidden;
  margin: 0.75rem 0 1.25rem;
}

.progress-bar > span {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--teal), var(--coral));
  transition: width 0.4s ease;
}

@media (max-width: 860px) {
  .brand-logo {
    height: 40px;
    width: 40px;
  }

  .topic-layout {
    grid-template-columns: 1fr;
  }

  .toc {
    position: static;
  }

  .stats {
    grid-template-columns: 1fr 1fr;
  }

  .nav-toggle {
    display: inline-flex;
  }

  .nav {
    display: none;
    width: 100%;
    flex-direction: column;
    align-items: flex-start;
  }

  .nav.open {
    display: flex;
  }

  .header-inner {
    flex-wrap: wrap;
  }

  .paper {
    padding: 1rem;
    border-radius: 12px;
  }

  .paper-logo {
    height: 56px;
  }

  .paper-nav {
    gap: 0.35rem;
  }

  .paper-nav button {
    flex: 1 1 calc(33.33% - 0.35rem);
    min-width: 4.5rem;
    padding: 0.45rem 0.4rem;
    font-size: 0.8rem;
  }

  .paper-toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .paper-toolbar .btn {
    width: 100%;
  }

  .paper-meta {
    gap: 0.4rem;
  }

  .paper-meta span {
    font-size: 0.78rem;
  }

  .case-q {
    padding: 0.85rem;
  }

  .paper-explain .en-block,
  .paper-explain .rom-block {
    padding: 0.75rem;
  }

  #paper-mcq-form .options {
    gap: 0.5rem;
  }

  .callout.exam {
    font-size: 0.88rem;
  }
}

@media (max-width: 480px) {
  .stats {
    grid-template-columns: 1fr;
  }

  .wrap {
    padding: 1rem 0.85rem 3rem;
  }

  .paper-nav button {
    flex: 1 1 calc(50% - 0.35rem);
  }
}

@media print {
  .site-header,
  .nav,
  .lang-tabs,
  .toc,
  .site-footer,
  .toggle-sol,
  .hero-actions {
    display: none !important;
  }

  body {
    background: #fff;
  }

  .paper {
    box-shadow: none;
    border: none;
  }
}