:root {
  color-scheme: light;
  --ink: #1c2430;
  --muted: #5c6778;
  --line: #b9c2ce;
  --field-line: #6b7686;
  --accent: #1f6b4a;
  --accent-soft: #e8f4ee;
  --bg: #f6f7f9;
  --card: #ffffff;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Segoe UI", "PingFang TC", "Microsoft JhengHei", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, #eef6f1 0, transparent 32rem),
    var(--bg);
}

main {
  max-width: 40rem;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 3rem;
  touch-action: pan-y;
}

.badge {
  display: inline-block;
  margin: 0 0 0.85rem;
  padding: 0.25rem 0.7rem;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 0.85rem;
  font-weight: 600;
}

h1 {
  margin: 0 0 0.5rem;
  font-size: clamp(1.7rem, 5vw, 2.4rem);
  line-height: 1.25;
}

.lead, .meta {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.site-stats {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.6rem;
  margin-top: 1rem;
}

.site-stat {
  min-width: 0;
  padding: 0.75rem 0.65rem;
  border: 1.5px solid var(--line);
  border-radius: 0.7rem;
  background: rgba(255, 255, 255, 0.78);
}

.site-stat strong,
.site-stat span {
  display: block;
  text-align: center;
}

.site-stat strong {
  font-size: 1.2rem;
  line-height: 1.2;
}

.site-stat span {
  margin-top: 0.2rem;
  color: var(--muted);
  font-size: 0.82rem;
}

.ranking-panel {
  display: grid;
  gap: 0.85rem;
  margin-top: 1.25rem;
}

.ranking-search {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.65rem;
  align-items: end;
}

.ranking-search input {
  width: 100%;
  min-width: 0;
  padding: 0.85rem 0.9rem;
  border: 2px solid var(--field-line);
  border-radius: 0.75rem;
  background: white;
  color: var(--ink);
  font: inherit;
}

.ranking-table-wrap {
  width: 100%;
  overflow-x: auto;
  border: 1.5px solid var(--line);
  border-radius: 0.8rem;
  background: var(--card);
}

.ranking-table {
  width: 100%;
  min-width: 42rem;
  border-collapse: collapse;
  font-size: 0.92rem;
}

.ranking-table th,
.ranking-table td {
  padding: 0.7rem 0.8rem;
  border-bottom: 1px solid var(--line);
  text-align: right;
  white-space: nowrap;
}

.ranking-table th:nth-child(2),
.ranking-table td:nth-child(2) {
  text-align: left;
  min-width: 12rem;
}

.ranking-table thead th {
  background: #f0f5f2;
  color: #314337;
  font-weight: 700;
}

.ranking-table tbody tr:last-child th,
.ranking-table tbody tr:last-child td {
  border-bottom: 0;
}

.countdown {
  margin-top: 0.35rem;
  font-weight: 700;
  color: var(--ink);
}

.countdown.ended {
  color: #b42318;
}

.choices, .options {
  display: grid;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

a.choice, a.nav, button.option, button.nav {
  font: inherit;
  text-align: left;
  border: 1.5px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 0.9rem;
  padding: 0.95rem 1rem;
  cursor: pointer;
}

a.choice, a.nav {
  display: block;
  text-decoration: none;
}

button.choice {
  font: inherit;
  width: 100%;
  text-align: left;
  border: 1.5px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 0.9rem;
  padding: 0.95rem 1rem;
  cursor: pointer;
}

button.choice strong, a.choice strong, button.option strong {
  display: block;
  margin-bottom: 0.15rem;
}

a.choice span, button.option span {
  color: var(--muted);
  font-size: 0.92rem;
}

.option-image {
  display: block;
  max-width: 100%;
  max-height: 12rem;
  margin-top: 0.65rem;
  border: 1.5px solid var(--line);
  border-radius: 0.55rem;
  background: white;
}

a.choice:hover, a.nav:hover, button.option:hover, button.nav:hover {
  border-color: #5f9e80;
}

.pager {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.pager button.nav {
  padding: 0.55rem 0.9rem;
}

.pager button.nav.current {
  border-color: var(--accent);
  background: var(--accent-soft);
  font-weight: 700;
}

button.option.selected {
  border-color: var(--accent);
  background: var(--accent-soft);
}

button.option.correct {
  border-color: #21835a;
  background: #e8f4ee;
}

button.option.wrong {
  border-color: #d05b4d;
  background: #fff0ee;
}

.answer-feedback {
  margin-top: 1rem;
  padding: 0.85rem 1rem;
  border: 1.5px solid var(--line);
  border-radius: 0.8rem;
  background: var(--card);
  color: var(--muted);
  line-height: 1.5;
}

.answer-feedback.correct {
  border-color: #9fceb7;
  background: #eef8f3;
  color: #145f40;
}

.answer-feedback.wrong,
.answer-feedback.error {
  border-color: #efb3aa;
  background: #fff3f1;
  color: #9f2f24;
}

img.figure {
  display: block;
  width: 100%;
  height: auto;
  margin-top: 1rem;
  border: 1.5px solid var(--line);
  border-radius: 0.7rem;
  background: white;
}

.upload {
  display: grid;
  gap: 0.9rem;
  margin-top: 1.5rem;
}

.upload-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  align-items: end;
}

.upload-row[hidden] {
  display: none;
}

.ocr-block {
  display: grid;
  gap: 0.45rem;
  margin-top: 0.35rem;
}

.ocr-block .ocr-image-field {
  margin: 0;
}

.ocr-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  align-items: center;
}

.ocr-row .meta {
  margin: 0;
  flex: 1 1 14rem;
}

.meta.warn {
  color: #9a5b14;
}

.nav.secondary {
  background: white;
  color: var(--ink);
  border: 1.5px solid var(--line);
}

.upload-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
}

.nav.danger {
  background: white;
  color: #b42318;
  border-color: #e8b4ae;
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.upload > .ocr-block {
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

.paper-ocr-block {
  display: grid;
  gap: 0.75rem;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

.paper-ocr-image-field {
  margin: 0;
}

.paper-answer-sheet {
  display: grid;
  gap: 0.75rem;
  border-top: 1px dashed var(--line);
  padding-top: 0.75rem;
}

.paper-ocr-results {
  display: grid;
  gap: 0.75rem;
}

.paper-draft-list {
  display: grid;
  gap: 0.75rem;
}

.paper-draft {
  display: grid;
  gap: 0.55rem;
  padding: 0.75rem;
  border: 1.5px solid var(--line);
  border-radius: 0.5rem;
  background: #fbfcfd;
}

.paper-draft-head {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.65rem;
  align-items: center;
}

.paper-draft-head h3 {
  margin: 0;
  font-size: 1rem;
}

.paper-draft-head .nav {
  width: auto;
  padding: 0.55rem 0.8rem;
}

.paper-draft.saved {
  border-color: var(--accent);
  background: var(--accent-soft);
}

.paper-draft .field {
  margin: 0;
}

.paper-draft-option-fields {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.55rem 0.75rem;
}

.upload + .paper-ocr-block {
  margin-top: 1rem;
}

.paper-upload-actions {
  display: grid;
  gap: 0.5rem;
  margin-top: 1rem;
}

.paper-filters {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(9rem, 1fr));
  gap: 0.75rem;
  margin: 1rem 0;
}

.paper-search {
  grid-column: 1 / -1;
}

.upload-tabs {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.4rem;
  margin-top: 1rem;
  padding: 0.3rem;
  border: 1.5px solid var(--line);
  border-radius: 0.7rem;
  background: white;
}

.upload-tabs a {
  padding: 0.6rem 0.75rem;
  border-radius: 0.5rem;
  color: var(--ink);
  text-align: center;
  text-decoration: none;
  font-weight: 600;
}

.upload-tabs a.active {
  background: var(--accent);
  color: white;
}

.paper-draft-stem {
  margin: 0;
  line-height: 1.6;
  white-space: pre-wrap;
}

.paper-draft-options {
  margin: 0;
  padding-left: 1.25rem;
  display: grid;
  gap: 0.25rem;
}

.file-chip {
  display: inline-flex;
  max-width: 100%;
  padding: 0.45rem 0.65rem;
  border: 1.5px solid var(--line);
  border-radius: 0.5rem;
  background: white;
  color: var(--ink);
  font-weight: 650;
  overflow-wrap: anywhere;
}

.option-editor {
  display: grid;
  gap: 0.75rem;
}

.option-fields {
  display: grid;
  gap: 0.75rem;
}

.option-row {
  display: grid;
  gap: 0.6rem;
  padding: 0.75rem;
  border: 1.5px solid var(--line);
  border-radius: 0.8rem;
  background: #fbfcfd;
}

.option-image-field .paste-box {
  min-height: 5.5rem;
}

.option-image-field .paste-box img {
  max-height: 10rem;
}

.total-count {
  margin: 0;
  padding: 0.75rem 0.15rem;
  color: var(--ink);
  font-weight: 650;
  line-height: 1.4;
}

.field {
  display: grid;
  gap: 0.35rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.field input, .field textarea, .field select {
  width: 100%;
  font: inherit;
  color: var(--ink);
  border: 2px solid var(--field-line);
  border-radius: 0.8rem;
  padding: 0.75rem 0.9rem;
  background: var(--card);
}

.field input:focus, .field textarea:focus, .field select:focus,
.ranking-search input:focus, .timer-minutes input:focus {
  border-color: var(--accent);
  outline: none;
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.field textarea {
  min-height: 8rem;
  resize: vertical;
}

.field[hidden],
.field input[hidden],
.field select[hidden] {
  display: none;
}

.paste-box {
  min-height: 7.5rem;
  display: grid;
  place-items: center;
  padding: 0.75rem;
  border: 2px dashed var(--field-line);
  border-radius: 0.8rem;
  background: var(--card);
  color: var(--muted);
  text-align: center;
  line-height: 1.5;
  cursor: text;
}

.paste-box:focus {
  border-color: var(--accent);
  outline: none;
}

.paste-box img {
  display: block;
  max-width: 100%;
  max-height: 16rem;
  border: 0;
  border-radius: 0.4rem;
}

h2 {
  margin: 2rem 0 0.4rem;
  font-size: 1.2rem;
}

.stem {
  margin: 1.25rem 0 0;
  font-size: 1.25rem;
  line-height: 1.55;
}

.stem-preview {
  margin: 0;
  padding: 0.9rem 1rem;
  border: 1.5px solid var(--line);
  border-radius: 0.8rem;
  background: white;
  font-size: 1.15rem;
  line-height: 1.55;
}

.math-inline {
  display: inline-block;
  margin: 0 0.05em;
  vertical-align: baseline;
}

.math-inline .katex {
  font-size: 1.05em;
}

.option .math-inline .katex {
  font-size: 1em;
}

.chem-inline sub,
.chem-inline sup {
  font-size: 0.72em;
  line-height: 0;
}

.chem-inline sub {
  vertical-align: -0.35em;
}

.chem-inline sup {
  vertical-align: 0.45em;
}

.speeds {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin-top: 1.25rem;
}

.speeds span {
  color: var(--muted);
  font-size: 0.92rem;
  white-space: nowrap;
}

button.speed {
  font: inherit;
  border: 1.5px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 999px;
  padding: 0.4rem 0.85rem;
  cursor: pointer;
  white-space: nowrap;
}

button.speed.selected {
  border-color: transparent;
  background: var(--accent);
  color: white;
}

.practice-tools {
  display: grid;
  gap: 0.85rem;
  margin-top: 1.25rem;
  padding: 0.9rem;
  border: 1.5px solid var(--line);
  border-radius: 0.8rem;
  background: var(--card);
}

.practice-tools.compact {
  padding: 0.75rem 0.85rem;
}

.tool-title {
  color: var(--ink);
  font-size: 1rem;
}

.practice-tools .speeds {
  margin-top: 0;
}

.tool-toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--ink);
  cursor: pointer;
}

.tool-toggle input {
  width: 1.1rem;
  height: 1.1rem;
  margin: 0;
}

.timer-tool {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.6rem;
}

.timer-minutes {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--muted);
}

.timer-minutes input {
  width: 5rem;
  font: inherit;
  color: var(--ink);
  border: 2px solid var(--field-line);
  border-radius: 0.7rem;
  padding: 0.4rem 0.55rem;
}

.timer-minutes input[type="checkbox"] {
  width: 1.1rem;
  height: 1.1rem;
  margin: 0;
  padding: 0;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 1.5rem;
}

button.nav, a.nav {
  background: var(--accent);
  color: white;
  border-color: transparent;
}

button.nav.secondary {
  background: var(--card);
  color: var(--ink);
  border-color: var(--line);
}

button:disabled {
  opacity: 0.45;
  cursor: default;
}

.error {
  margin-top: 1rem;
  color: #8a2f2f;
}

.account-bar {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.75rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--line);
}

.account-bar span {
  flex: 1;
  min-width: 0;
  overflow-wrap: anywhere;
}

.auth-form {
  max-width: 32rem;
}

.remember-login {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  cursor: pointer;
}

.remember-login input {
  width: 1.1rem;
  height: 1.1rem;
  margin: 0;
  flex: none;
}

.social-login-hint {
  margin: 1rem 0 0.4rem;
  color: #4b5563;
}

.social-login {
  margin-bottom: 1rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr));
  gap: 0.6rem;
}