:root {
  --paper: #f7f2e8;
  --surface: #fffdf8;
  --surface-strong: #fff7e6;
  --ink: #18202a;
  --muted: #5f6670;
  --line: #dfd6c5;
  --teal: #006d77;
  --coral: #bd4635;
  --blue: #254f9a;
  --gold: #b77a12;
  --green: #386641;
  --shadow: 0 18px 45px rgba(45, 34, 20, 0.11);
  --radius: 8px;
  color-scheme: light;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 320px;
  background: var(--paper);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
}

svg {
  display: block;
  fill: none;
  stroke: currentColor;
  stroke-linecap: round;
  stroke-linejoin: round;
  stroke-width: 2;
}

.app-shell {
  width: min(1160px, calc(100% - 32px));
  margin: 0 auto;
  padding: 18px 0 56px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 12px 0 26px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: inherit;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  width: 46px;
  height: 46px;
  place-items: center;
  border: 2px solid var(--ink);
  border-radius: var(--radius);
  background: var(--teal);
  color: #fffdf8;
  font-size: 0.88rem;
  font-weight: 800;
  letter-spacing: 0;
  box-shadow: 5px 5px 0 var(--ink);
}

.brand strong,
.brand small {
  display: block;
}

.brand strong {
  font-size: 1.1rem;
  line-height: 1.1;
}

.brand small {
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.3;
}

.subject-tabs {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
  min-width: min(100%, 390px);
  padding: 6px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(255, 253, 248, 0.72);
}

.tab-button {
  min-height: 44px;
  border: 1px solid transparent;
  border-radius: 6px;
  background: transparent;
  color: var(--muted);
  font-weight: 750;
  transition: background 180ms ease, color 180ms ease, border-color 180ms ease, transform 180ms ease;
}

.tab-button:hover,
.tab-button:focus-visible {
  border-color: var(--line);
  background: var(--surface);
  color: var(--ink);
}

.tab-button:focus-visible,
.icon-button:focus-visible,
.question-head:focus-visible,
.dsa-group-head:focus-visible,
.search-box:focus-within {
  outline: 3px solid rgba(0, 109, 119, 0.3);
  outline-offset: 2px;
}

.tab-button.is-active {
  background: var(--ink);
  color: #fffdf8;
}

.study-toolbar {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 430px);
  gap: 26px;
  align-items: end;
  padding: 34px;
  border: 2px solid var(--ink);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--coral);
  font-size: 0.78rem;
  font-weight: 850;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  max-width: 760px;
  margin-bottom: 0;
  font-size: clamp(2rem, 5vw, 4.25rem);
  line-height: 1.02;
  letter-spacing: 0;
}

.toolbar-actions {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 48px;
  gap: 10px;
}

.search-box {
  display: grid;
  grid-template-columns: 22px minmax(0, 1fr);
  align-items: center;
  gap: 10px;
  min-height: 48px;
  padding: 0 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.search-box svg {
  width: 20px;
  height: 20px;
  color: var(--teal);
}

.search-box input {
  width: 100%;
  border: 0;
  outline: 0;
  background: transparent;
  color: var(--ink);
  font-size: 1rem;
}

.icon-button {
  display: grid;
  width: 48px;
  height: 48px;
  place-items: center;
  border: 1px solid var(--ink);
  border-radius: var(--radius);
  background: var(--gold);
  color: var(--ink);
  transition: transform 180ms ease, box-shadow 180ms ease, background 180ms ease;
}

.icon-button:hover {
  transform: translate(-2px, -2px);
  box-shadow: 4px 4px 0 var(--ink);
}

.icon-button svg {
  width: 22px;
  height: 22px;
}

.subject-strip {
  display: grid;
  grid-template-columns: 76px minmax(0, 1fr) auto;
  gap: 18px;
  align-items: center;
  margin: 26px 0 18px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: rgba(255, 253, 248, 0.9);
}

.subject-badge {
  display: grid;
  width: 64px;
  height: 64px;
  place-items: center;
  border: 2px solid var(--ink);
  border-radius: var(--radius);
  background: var(--teal);
  color: #fff;
  font-weight: 900;
}

.subject-strip h2 {
  margin-bottom: 2px;
  font-size: 1.45rem;
  line-height: 1.2;
}

.subject-strip p {
  max-width: 760px;
  margin-bottom: 0;
  color: var(--muted);
}

.quick-stats {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 8px;
}

.quick-stats span {
  min-height: 36px;
  padding: 6px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface-strong);
  color: var(--ink);
  font-size: 0.9rem;
  white-space: nowrap;
}

.question-list {
  display: grid;
  gap: 14px;
}

.dsa-question-group {
  display: grid;
  gap: 14px;
}

.dsa-group-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto 28px;
  gap: 14px;
  align-items: center;
  width: 100%;
  min-height: 68px;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-left: 7px solid var(--coral);
  border-radius: var(--radius);
  background: var(--surface);
  color: inherit;
  text-align: left;
  transition: border-color 180ms ease, background 180ms ease, transform 180ms ease;
}

.dsa-group-head:hover {
  border-color: var(--ink);
  background: var(--surface-strong);
}

.dsa-group-title {
  font-size: 1.05rem;
  font-weight: 850;
  line-height: 1.25;
}

.dsa-group-count {
  min-height: 34px;
  padding: 5px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 750;
  white-space: nowrap;
}

.dsa-group-head svg {
  width: 24px;
  height: 24px;
  justify-self: end;
  color: var(--muted);
  transition: transform 180ms ease;
}

.dsa-question-group.is-open .dsa-group-head svg {
  transform: rotate(180deg);
}

.dsa-group-body {
  display: grid;
  gap: 14px;
}

.dsa-group-body:empty {
  display: none;
}

.question-card {
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.question-card[data-subject="web-dev"] {
  border-left: 7px solid var(--teal);
}

.question-card[data-subject="dbms"] {
  border-left: 7px solid var(--blue);
}

.question-card[data-subject="dsa-cpp"] {
  border-left: 7px solid var(--coral);
}

.question-head {
  display: grid;
  grid-template-columns: 46px minmax(0, 1fr) 28px;
  gap: 14px;
  align-items: center;
  width: 100%;
  min-height: 78px;
  padding: 16px 18px;
  border: 0;
  background: transparent;
  color: inherit;
  text-align: left;
}

.question-number {
  display: grid;
  width: 42px;
  height: 42px;
  place-items: center;
  border: 1px solid var(--ink);
  border-radius: 6px;
  background: var(--surface-strong);
  font-weight: 850;
}

.question-title {
  font-size: 1.08rem;
  font-weight: 800;
  line-height: 1.35;
}

.question-head svg {
  width: 24px;
  height: 24px;
  justify-self: end;
  color: var(--muted);
  transition: transform 180ms ease;
}

.question-card.is-open .question-head svg {
  transform: rotate(180deg);
}

.question-body {
  display: none;
  padding: 0 18px 22px 78px;
}

.question-card.is-open .question-body {
  display: block;
}

.meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 16px;
}

.meta-chip {
  padding: 4px 9px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 700;
}

.answer-content {
  max-width: 830px;
  color: #26313d;
}

.answer-content h3 {
  margin: 22px 0 8px;
  font-size: 1rem;
  line-height: 1.3;
}

.answer-content p {
  margin-bottom: 12px;
}

.answer-content ul,
.answer-content ol {
  margin: 0 0 14px 20px;
  padding: 0;
}

.answer-content li {
  margin-bottom: 7px;
}

.answer-content code {
  padding: 2px 5px;
  border-radius: 4px;
  background: #f1eadb;
  color: #111827;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.93em;
}

.answer-content pre {
  overflow-x: auto;
  margin: 14px 0;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #16202a;
  color: #fffdf8;
}

.answer-content pre code {
  padding: 0;
  background: transparent;
  color: inherit;
}

.empty-state {
  margin: 24px 0 0;
  padding: 22px;
  border: 1px dashed var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--muted);
  text-align: center;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}

@media (max-width: 820px) {
  .topbar,
  .study-toolbar,
  .subject-strip {
    grid-template-columns: 1fr;
  }

  .topbar {
    align-items: stretch;
  }

  .subject-tabs {
    min-width: 0;
  }

  .study-toolbar {
    padding: 24px;
  }

  .subject-strip {
    grid-template-columns: 60px minmax(0, 1fr);
  }

  .subject-badge {
    width: 56px;
    height: 56px;
  }

  .quick-stats {
    grid-column: 1 / -1;
    justify-content: flex-start;
  }

  .question-body {
    padding-left: 18px;
  }
}

@media (max-width: 560px) {
  .app-shell {
    width: min(100% - 20px, 1160px);
    padding-top: 10px;
  }

  .subject-tabs {
    grid-template-columns: 1fr;
  }

  .toolbar-actions {
    grid-template-columns: 1fr 48px;
  }

  .question-head {
    grid-template-columns: 38px minmax(0, 1fr) 22px;
    gap: 10px;
    padding: 14px;
  }

  .dsa-group-head {
    grid-template-columns: minmax(0, 1fr) 22px;
  }

  .dsa-group-head svg {
    grid-column: 2;
    grid-row: 1;
  }

  .dsa-group-count {
    grid-column: 1 / -1;
    grid-row: 2;
    justify-self: start;
  }

  .question-number {
    width: 36px;
    height: 36px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition: none !important;
  }
}

@media print {
  body {
    background: #fff;
  }

  .topbar,
  .toolbar-actions,
  .subject-tabs {
    display: none;
  }

  .app-shell {
    width: 100%;
    padding: 0;
  }

  .study-toolbar,
  .subject-strip,
  .question-card {
    border-color: #999;
    box-shadow: none;
  }

  .question-body {
    display: block;
  }
}