:root {
  color-scheme: light;
  --bg: #f7f9fc;
  --surface: #ffffff;
  --surface-soft: #f4f7fb;
  --text: #111827;
  --muted: #64748b;
  --border: #dbe2ea;
  --blue: #2563eb;
  --blue-soft: #eaf1ff;
  --green: #16a34a;
  --green-soft: #e9f8ef;
  --amber: #f59e0b;
  --red: #dc2626;
  --shadow: 0 18px 50px rgba(15, 23, 42, 0.08);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "Apple SD Gothic Neo", "Noto Sans KR", sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
}

button,
input,
textarea {
  font: inherit;
}

button {
  cursor: pointer;
}

.app-shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 280px minmax(560px, 1fr) 420px;
}

.sidebar,
.right-panel {
  background: rgba(255, 255, 255, 0.86);
  border-color: var(--border);
  border-style: solid;
}

.sidebar {
  border-width: 0 1px 0 0;
  padding: 24px 20px;
  display: flex;
  flex-direction: column;
  gap: 22px;
}

.right-panel {
  border-width: 0 0 0 1px;
  padding: 20px 20px;
  overflow: auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.side-brand,
.brand-row {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  width: 28px;
  height: 28px;
  border-radius: 8px;
  display: inline-grid;
  place-items: center;
  color: var(--blue);
  background: linear-gradient(90deg, var(--blue) 0 48%, var(--green) 48% 100%);
  font-size: 0;
}

.side-brand h1,
.brand-row h1 {
  margin: 0;
  font-size: 20px;
  line-height: 1.2;
}

.side-brand p,
.brand-row p {
  margin: 3px 0 0;
  color: var(--blue);
  font-size: 13px;
}

.account-box,
.sync-box,
.stat-card,
.queue-card,
.editor-card,
.flashcard,
.upcoming-panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  box-shadow: 0 1px 0 rgba(15, 23, 42, 0.03);
}

.account-box {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px;
}

.avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: var(--blue-soft);
  color: var(--blue);
  font-weight: 800;
}

.account-box strong,
.account-box span {
  display: block;
}

.account-box span {
  margin-top: 4px;
  color: var(--muted);
  font-size: 13px;
}

.sync-box,
.stat-card {
  padding: 14px;
}

.sync-line,
.section-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.status-badge {
  font-size: 12px;
  color: var(--green);
  background: var(--green-soft);
  padding: 4px 8px;
  border-radius: 999px;
  font-weight: 700;
}

.sync-box p {
  margin: 10px 0 12px;
  color: var(--muted);
  font-size: 13px;
}

.ghost-button,
.secondary-button,
.icon-button,
.danger-button,
.save-button,
.known-button,
.again-button,
.logout-form button,
.nav-item {
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  min-height: 40px;
  padding: 0 14px;
  font-weight: 700;
}

.ghost-button,
.logout-form button {
  width: 100%;
  color: var(--blue);
}

.side-nav {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.nav-item {
  display: grid;
  grid-template-columns: 24px 1fr auto;
  align-items: center;
  gap: 10px;
  text-align: left;
  color: #334155;
}

.nav-item.active {
  border-color: var(--blue);
  background: var(--blue-soft);
  color: var(--blue);
}

.nav-item b {
  min-width: 28px;
  min-height: 24px;
  border-radius: 999px;
  display: inline-grid;
  place-items: center;
  background: rgba(37, 99, 235, 0.12);
  font-size: 12px;
}

.stat-card {
  margin-top: auto;
  display: grid;
  gap: 13px;
}

.stat-card div {
  display: flex;
  justify-content: space-between;
  color: var(--muted);
  font-size: 14px;
}

.stat-card strong {
  color: var(--text);
}

.logout-form {
  margin: 0;
}

.study-main {
  min-width: 0;
  padding: 28px;
  overflow: auto;
}

.main-toolbar {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 18px;
}

.main-toolbar h2 {
  margin: 0;
  font-size: 26px;
}

.main-toolbar p {
  margin: 7px 0 0;
  color: var(--muted);
}

.toolbar-actions {
  display: flex;
  gap: 10px;
}

.icon-button {
  width: 42px;
  padding: 0;
  display: inline-grid;
  place-items: center;
  color: #334155;
  font-size: 18px;
}

.category-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin: 24px 0 20px;
}

.chip {
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: #334155;
  padding: 8px 12px;
  min-height: 36px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  font-size: 14px;
}

.chip.selected {
  border-color: var(--blue);
  background: var(--blue-soft);
  color: var(--blue);
}

.chip.soft {
  color: var(--green);
  background: var(--green-soft);
  border-color: transparent;
}

.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: currentColor;
}

.flashcard {
  min-height: 540px;
  padding: 22px;
  box-shadow: var(--shadow);
}

.card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.card-actions {
  display: flex;
  gap: 8px;
}

.card-body {
  min-height: 330px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  border-bottom: 1px solid var(--border);
  padding: 26px 20px;
}

.card-body h3 {
  margin: 0;
  font-size: clamp(44px, 5.2vw, 72px);
  line-height: 1.08;
  letter-spacing: 0;
}

.card-body > p {
  margin: 18px 0 18px;
  color: #475569;
  font-size: 25px;
}

.answer-area {
  width: min(100%, 700px);
  display: grid;
  gap: 18px;
  margin-top: 22px;
  text-align: left;
}

.answer-area div {
  background: var(--surface-soft);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 16px;
}

.answer-area span,
.term-form span,
.field-label {
  display: block;
  color: var(--blue);
  font-size: 13px;
  font-weight: 800;
  margin-bottom: 8px;
}

.answer-area p {
  margin: 0;
  line-height: 1.65;
}

.hidden {
  display: none !important;
}

.review-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin: 20px 0;
}

.known-button {
  background: var(--green);
  border-color: var(--green);
  color: white;
  min-height: 58px;
}

.again-button,
.save-button {
  background: var(--blue);
  border-color: var(--blue);
  color: white;
  min-height: 58px;
}

.card-progress {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 12px;
  color: var(--muted);
  font-size: 13px;
}

.progress-track {
  height: 8px;
  border-radius: 999px;
  background: #e5eaf0;
  overflow: hidden;
}

.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  background: var(--green);
}

.upcoming-panel,
.queue-card,
.editor-card {
  padding: 14px;
}

.section-heading h3 {
  margin: 0;
  font-size: 18px;
}

.section-heading button,
.section-heading input {
  min-height: 38px;
}

.section-heading input {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0 12px;
  width: 170px;
}

.grouped-list,
.queue-list {
  margin-top: 16px;
  display: grid;
  gap: 8px;
}

.queue-card {
  max-height: 170px;
  overflow: hidden;
}

.queue-list {
  max-height: 92px;
  overflow: auto;
  padding-right: 4px;
}

.group-title {
  margin: 14px 0 4px;
  color: var(--green);
  font-weight: 800;
}

.term-row {
  min-height: 46px;
  border-top: 1px solid var(--border);
  display: grid;
  grid-template-columns: 1fr auto auto;
  align-items: center;
  gap: 12px;
  color: #334155;
}

.term-row button {
  border: 0;
  background: transparent;
  text-align: left;
  padding: 0;
  color: inherit;
}

.term-row small {
  color: var(--muted);
  font-size: 12px;
}

.pill {
  border-radius: 999px;
  padding: 4px 8px;
  background: var(--blue-soft);
  color: var(--blue);
  font-size: 12px;
  font-weight: 800;
}

.term-form {
  display: grid;
  gap: 7px;
  margin-top: 12px;
}

.term-form input,
.term-form textarea,
.new-category-row input {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  padding: 9px 10px;
  resize: vertical;
}

.term-form textarea {
  min-height: 58px;
  max-height: 68px;
}

.editor-categories {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.editor-categories .chip {
  min-height: 30px;
  padding: 5px 8px;
  font-size: 12px;
}

.new-category-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 8px;
}

.form-actions {
  display: grid;
  grid-template-columns: auto 1fr 1fr;
  gap: 10px;
}

.danger-button {
  color: var(--red);
}

.login-body {
  min-height: 100vh;
  display: grid;
  place-items: center;
}

.login-shell {
  width: min(100%, 420px);
  padding: 24px;
}

.login-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 26px;
  box-shadow: var(--shadow);
}

.login-form {
  display: grid;
  gap: 16px;
  margin-top: 24px;
}

.login-form span {
  display: block;
  font-weight: 800;
  font-size: 13px;
  margin-bottom: 8px;
}

.login-form input {
  width: 100%;
  min-height: 46px;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0 12px;
}

.login-form button {
  min-height: 48px;
  border: 1px solid var(--blue);
  border-radius: 8px;
  background: var(--blue);
  color: white;
  font-weight: 800;
}

.form-error {
  margin: 0;
  color: var(--red);
  font-weight: 700;
}

@media (max-width: 1180px) {
  .app-shell {
    grid-template-columns: 220px minmax(0, 1fr);
  }

  .right-panel {
    grid-column: 1 / -1;
    border-width: 1px 0 0;
    display: grid;
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 760px) {
  .app-shell {
    display: block;
  }

  .sidebar {
    border-width: 0 0 1px;
  }

  .side-nav,
  .stat-card,
  .logout-form {
    display: none;
  }

  .study-main,
  .right-panel {
    padding: 18px;
  }

  .right-panel {
    display: block;
  }

  .editor-card {
    margin-top: 18px;
  }

  .main-toolbar,
  .card-progress {
    display: block;
  }

  .toolbar-actions {
    margin-top: 14px;
  }

  .flashcard {
    min-height: auto;
  }

  .card-body h3 {
    font-size: 42px;
  }

  .review-actions,
  .form-actions {
    grid-template-columns: 1fr;
  }
}