:root {
  --bg: #f5f6fb;
  --surface: #ffffff;
  --surface-2: #eef1f8;
  --text: #121826;
  --muted: #5c667a;
  --border: #d9deeb;
  --accent: #2957d9;
  --accent-soft: #e8edff;
  --success: #187a3f;
  --danger: #b42318;
  --warning: #9a6700;
  --shadow: 0 18px 45px rgba(15, 23, 42, 0.08);
  --radius: 22px;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

[data-theme="dark"] {
  --bg: #0f1421;
  --surface: #151b2b;
  --surface-2: #1f283c;
  --text: #f6f8ff;
  --muted: #a7b0c4;
  --border: #2b3752;
  --accent: #89a5ff;
  --accent-soft: #1f2a4c;
  --success: #66d18f;
  --danger: #ff8a80;
  --warning: #ffd166;
  --shadow: 0 18px 45px rgba(0, 0, 0, 0.24);
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 10% 0%, rgba(41, 87, 217, 0.13), transparent 28rem),
    radial-gradient(circle at 100% 10%, rgba(125, 83, 255, 0.10), transparent 25rem),
    var(--bg);
  color: var(--text);
  font-family: var(--sans);
}

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

button {
  border: 0;
  border-radius: 999px;
  background: var(--accent);
  color: white;
  cursor: pointer;
  padding: 0.72rem 1rem;
  font-weight: 700;
  transition: transform 140ms ease, opacity 140ms ease, background 140ms ease;
}

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

button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
  transform: none;
}

.secondary-btn,
.ghost-btn,
.mode-btn {
  background: var(--surface-2);
  color: var(--text);
}

.ghost-btn {
  border: 1px solid var(--border);
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  max-width: 1220px;
  margin: 0 auto;
  padding: 2rem 1.2rem 1rem;
}

.eyebrow {
  margin: 0 0 0.35rem;
  color: var(--accent);
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.76rem;
}

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

h1 {
  margin-bottom: 0;
  font-size: clamp(2rem, 5vw, 4rem);
  line-height: 0.95;
}

h2 {
  font-size: 1.1rem;
}

.app-shell {
  max-width: 1220px;
  margin: 0 auto;
  padding: 1rem 1.2rem 4rem;
}

.panel {
  background: color-mix(in srgb, var(--surface) 94%, transparent);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}

.upload-panel,
.summary-panel {
  padding: 1.2rem;
  margin-bottom: 1rem;
}

.panel-heading {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.panel-heading p,
.help-box p,
.summary-panel p,
.meta {
  color: var(--muted);
}

.upload-box {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 1rem;
  align-items: center;
  background: var(--surface-2);
  border: 1px dashed var(--border);
  border-radius: 18px;
  padding: 1rem;
}

.upload-actions,
.nav-actions,
.question-actions,
.answer-actions,
.mode-row {
  display: flex;
  gap: 0.65rem;
  flex-wrap: wrap;
  align-items: center;
}

input[type="file"] {
  width: 100%;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.75rem;
  color: var(--muted);
}

.help-box {
  margin-top: 1rem;
  color: var(--muted);
}

.help-box summary {
  cursor: pointer;
  color: var(--text);
  font-weight: 800;
}

code,
pre {
  font-family: var(--mono);
}

code {
  background: var(--surface-2);
  padding: 0.12rem 0.35rem;
  border-radius: 0.35rem;
}

.workspace {
  display: grid;
  grid-template-columns: 310px minmax(0, 1fr);
  gap: 1rem;
  align-items: start;
}

.question-list-panel,
.question-panel {
  padding: 1rem;
}

.question-list-panel {
  position: sticky;
  top: 1rem;
  max-height: calc(100vh - 2rem);
  overflow: auto;
}

.list-header {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  align-items: center;
  margin-bottom: 0.75rem;
}

.pill,
.level-pill,
.type-pill {
  display: inline-flex;
  align-items: center;
  min-height: 1.7rem;
  border-radius: 999px;
  padding: 0.25rem 0.6rem;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.82rem;
  font-weight: 800;
}

.mode-row {
  margin-bottom: 0.9rem;
}

.mode-btn {
  flex: 1;
  padding: 0.55rem 0.7rem;
}

.mode-btn.active {
  background: var(--accent);
  color: white;
}

.question-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0.45rem;
}

.question-list button {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 0.55rem;
  width: 100%;
  text-align: left;
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 0.7rem;
  font-weight: 700;
}

.question-list button.active {
  background: var(--accent-soft);
  border-color: color-mix(in srgb, var(--accent) 45%, var(--border));
}

.q-number {
  display: inline-grid;
  place-items: center;
  width: 1.6rem;
  height: 1.6rem;
  border-radius: 50%;
  background: var(--surface-2);
  font-size: 0.82rem;
}

.q-title {
  min-width: 0;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
}

.status-dot {
  width: 0.75rem;
  height: 0.75rem;
  border-radius: 50%;
  background: var(--border);
}

.status-dot.correct {
  background: var(--success);
}

.status-dot.wrong {
  background: var(--danger);
}

.status-dot.partial {
  background: var(--warning);
}

.question-header {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  align-items: flex-start;
  padding-bottom: 0.9rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 1rem;
}

.question-header h2 {
  margin-bottom: 0.4rem;
  font-size: clamp(1.35rem, 3vw, 2rem);
}

.question-body {
  font-size: 1.04rem;
  line-height: 1.65;
}

.math-display {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 1rem;
  margin: 1rem 0;
  overflow-x: auto;
}

.question-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0;
  overflow: hidden;
  border-radius: 14px;
}

.question-table th,
.question-table td {
  border: 1px solid var(--border);
  padding: 0.7rem;
  text-align: center;
}

.question-table th {
  background: var(--surface-2);
}

.choice-grid {
  display: grid;
  gap: 0.65rem;
  margin: 1rem 0;
}

.choice-card {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.65rem;
  align-items: center;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 0.85rem;
  cursor: pointer;
}

.choice-card input {
  inline-size: 1.05rem;
  block-size: 1.05rem;
}

.answer-block {
  margin-top: 1rem;
  padding: 1rem;
  border-radius: 18px;
  border: 1px solid var(--border);
  background: var(--surface-2);
}

.answer-block label {
  display: block;
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.answer-input,
textarea.answer-input {
  width: 100%;
  min-height: 4rem;
  resize: vertical;
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 0.85rem;
  font-family: var(--mono);
  line-height: 1.55;
}

.math-palette {
  display: flex;
  gap: 0.45rem;
  flex-wrap: wrap;
  margin: 0.7rem 0;
}

.math-palette button {
  background: var(--surface);
  color: var(--text);
  border: 1px solid var(--border);
  padding: 0.42rem 0.62rem;
  border-radius: 999px;
  font-size: 0.88rem;
}

.preview-box {
  min-height: 3.2rem;
  margin-top: 0.75rem;
  padding: 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow-x: auto;
}

.feedback {
  margin-top: 1rem;
  border-radius: 18px;
  padding: 1rem;
  border: 1px solid var(--border);
}

.feedback.correct {
  background: color-mix(in srgb, var(--success) 12%, var(--surface));
  border-color: color-mix(in srgb, var(--success) 35%, var(--border));
}

.feedback.wrong {
  background: color-mix(in srgb, var(--danger) 10%, var(--surface));
  border-color: color-mix(in srgb, var(--danger) 35%, var(--border));
}

.feedback.partial {
  background: color-mix(in srgb, var(--warning) 13%, var(--surface));
  border-color: color-mix(in srgb, var(--warning) 35%, var(--border));
}

.solution-list {
  margin: 0.5rem 0 0 1.2rem;
  padding: 0;
  line-height: 1.6;
}

.hint-box {
  margin-top: 1rem;
  padding: 0.9rem;
  border-radius: 16px;
  background: var(--surface-2);
  border: 1px solid var(--border);
}

.hidden {
  display: none !important;
}

.review-card {
  border: 1px solid var(--border);
  border-radius: 18px;
  padding: 1rem;
  margin-bottom: 1rem;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
}

.review-card h3 {
  margin-bottom: 0.4rem;
}

.footer-note {
  margin-top: 1rem;
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 860px) {
  .topbar {
    align-items: flex-start;
  }

  .upload-box,
  .workspace {
    grid-template-columns: 1fr;
  }

  .question-list-panel {
    position: static;
    max-height: none;
  }
}