:root {
  --bg: #f5f7fb;
  --fg: #142033;
  --muted: #5a667a;
  --card: #ffffff;
  --border: #dbe2ef;
  --input-border: #cbd5e1;
  --accent: #1f5fd2;
  --accent-soft: rgba(45, 108, 223, 0.16);
  --danger: #b42318;
  --ok: #137333;
  --shadow: 0 16px 44px rgba(20, 32, 51, 0.08);
  --chip: rgba(127, 127, 127, 0.08);
  color-scheme: light;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--fg);
}

:root[data-theme="dark"] {
  --bg: #0d1117;
  --fg: #e6edf3;
  --muted: #8b949e;
  --card: #161b22;
  --border: #30363d;
  --input-border: #30363d;
  --accent: #4d8bff;
  --accent-soft: rgba(77, 139, 255, 0.22);
  --danger: #ff6b6b;
  --ok: #3fb950;
  --shadow: 0 16px 44px rgba(0, 0, 0, 0.4);
  --chip: rgba(255, 255, 255, 0.06);
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  padding: 0 16px 48px;
}

/* topbar / nav */
.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 960px;
  margin: 0 auto;
  padding: 16px 0;
}

.brand {
  font-weight: 800;
  font-size: 20px;
  text-decoration: none;
  color: var(--fg);
}

.brand span {
  color: var(--accent);
}

.nav,
.auth-area {
  display: flex;
  align-items: center;
  gap: 10px;
}

.nav-link {
  color: var(--accent);
  text-decoration: none;
  font-weight: 600;
  font-size: 14px;
}

.nav-user {
  color: var(--muted);
  font-size: 13px;
  max-width: 180px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.nav-btn {
  border: 1px solid var(--accent);
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  font: inherit;
  font-size: 14px;
  font-weight: 700;
  padding: 8px 14px;
}

.nav-btn.ghost {
  background: transparent;
  color: var(--fg);
  border-color: var(--border);
}

.shell {
  width: min(720px, 100%);
  margin: 0 auto;
}

.hero {
  margin: 16px 0 24px;
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--accent);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.eyebrow a {
  color: inherit;
  text-decoration: none;
  text-transform: none;
}

.eyebrow a:hover {
  text-decoration: underline;
}

h1 {
  margin: 0;
  font-size: clamp(34px, 7vw, 58px);
  line-height: 1.05;
}

.summary {
  max-width: 640px;
  margin: 16px 0 0;
  color: var(--muted);
  font-size: 17px;
  line-height: 1.7;
}

.card,
.shorten-form {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  box-shadow: var(--shadow);
}

.shorten-form {
  display: grid;
  gap: 16px;
  padding: 24px;
}

.mode-switch {
  display: inline-flex;
  gap: 4px;
  background: var(--chip);
  border-radius: 10px;
  padding: 4px;
  width: fit-content;
}

.mode-tab {
  border: 0;
  background: transparent;
  color: var(--muted);
  border-radius: 8px;
  padding: 8px 16px;
  cursor: pointer;
  font: inherit;
  font-weight: 700;
}

.mode-tab.active {
  background: var(--card);
  color: var(--fg);
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.12);
}

.grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

label {
  display: block;
  margin-bottom: 8px;
  color: var(--fg);
  font-size: 14px;
  font-weight: 700;
}

input,
textarea {
  width: 100%;
  border: 1px solid var(--input-border);
  border-radius: 8px;
  padding: 12px 14px;
  color: var(--fg);
  background: var(--card);
  font: inherit;
  resize: vertical;
}

input:focus,
textarea:focus {
  border-color: var(--accent);
  outline: 3px solid var(--accent-soft);
}

.field-hint {
  margin: 6px 0 0;
  font-size: 13px;
  min-height: 16px;
  color: var(--muted);
}

.field-hint.ok {
  color: var(--ok);
}

.field-hint.bad {
  color: var(--danger);
}

button[type="submit"] {
  border: 0;
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  font: inherit;
  font-weight: 700;
  padding: 14px 16px;
}

button:disabled {
  cursor: wait;
  opacity: 0.65;
}

.btn-secondary {
  display: inline-block;
  border: 1px solid var(--accent);
  border-radius: 8px;
  background: transparent;
  color: var(--accent);
  cursor: pointer;
  font: inherit;
  font-weight: 700;
  padding: 10px 16px;
  text-decoration: none;
  text-align: center;
}

/* result card */
.result {
  margin-top: 16px;
  padding: 20px;
  display: grid;
  gap: 12px;
}

.result-row {
  display: grid;
  grid-template-columns: 80px 1fr;
  gap: 12px;
  align-items: baseline;
}

.result-label {
  color: var(--muted);
  font-weight: 700;
  font-size: 14px;
}

.result-value {
  overflow-wrap: anywhere;
  color: var(--fg);
}

#short-url {
  color: var(--accent);
  overflow-wrap: anywhere;
  font-weight: 700;
}

.result-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 4px;
}

.result-actions button,
#copy-button {
  border: 0;
  border-radius: 8px;
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  font: inherit;
  font-weight: 700;
  padding: 10px 16px;
}

.qr-box {
  margin-top: 8px;
  display: grid;
  gap: 12px;
  justify-items: center;
}

.qr-box svg {
  width: 200px;
  height: 200px;
  background: #fff;
  border-radius: 8px;
  padding: 8px;
}

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

/* batch */
.batch-result {
  margin-top: 16px;
  padding: 20px;
}

.batch-result h2 {
  margin: 0 0 12px;
  font-size: 18px;
}

#batch-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

#batch-list li {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
}

#batch-list a {
  color: var(--accent);
  font-weight: 700;
  overflow-wrap: anywhere;
}

#batch-list .src {
  color: var(--muted);
  font-size: 13px;
  width: 100%;
  overflow-wrap: anywhere;
}

#batch-list .link-copy {
  border: 1px solid var(--accent);
  background: transparent;
  color: var(--accent);
  border-radius: 6px;
  padding: 4px 10px;
  cursor: pointer;
  font-size: 13px;
}

#batch-list .failed .err {
  color: var(--danger);
  font-size: 13px;
}

.message {
  min-height: 24px;
  margin: 16px 0 0;
  color: var(--danger);
}

/* features */
.features {
  margin-top: 32px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.feature {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  padding: 16px;
  display: grid;
  gap: 6px;
}

.feature strong {
  font-size: 15px;
}

.feature span {
  color: var(--muted);
  font-size: 14px;
}

/* 管理後台頁籤 */
.admin-tabs {
  margin: 8px 0 24px;
}

/* 管理員每日用量資訊圖表 */
.usage-panel {
  margin-bottom: 36px;
}

.usage-day {
  color: var(--muted);
  font-size: 13px;
}

.usage-reset {
  margin: 0 0 16px;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--chip);
  color: var(--muted);
  font-size: 14px;
}

.usage-reset strong {
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.usage-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: 14px;
}

.usage-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  padding: 16px;
  box-shadow: var(--shadow);
}

.usage-card h4 {
  margin: 0 0 10px;
  font-size: 13px;
  color: var(--muted);
}

.usage-num {
  font-size: 26px;
  font-weight: 800;
  margin-bottom: 10px;
}

.usage-num span {
  font-size: 13px;
  font-weight: 600;
  color: var(--muted);
}

.usage-pct {
  margin-top: 6px;
  font-size: 13px;
  font-weight: 700;
  text-align: right;
}

.usage-trend-title {
  font-size: 16px;
  margin: 28px 0 12px;
}

.usage-trends {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 14px;
}

.trend {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  padding: 16px;
}

.trend h4 {
  margin: 0 0 12px;
  font-size: 13px;
  color: var(--muted);
}

.trend-rows {
  display: grid;
  gap: 6px;
}

.trend-row {
  display: grid;
  grid-template-columns: 44px 1fr 64px;
  align-items: center;
  gap: 8px;
  font-size: 12px;
}

.trend-day {
  color: var(--muted);
  white-space: nowrap;
}

.trend-val {
  text-align: right;
  color: var(--fg);
  font-variant-numeric: tabular-nums;
}

/* about / 用途說明 */
.about {
  margin-top: 32px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  padding: 24px;
  line-height: 1.8;
}

.about h2 {
  margin: 0 0 12px;
  font-size: 20px;
}

.about h3 {
  margin: 24px 0 8px;
  font-size: 16px;
}

.about ul {
  margin: 0 0 12px;
  padding-left: 20px;
}

.about li {
  margin-bottom: 8px;
  color: var(--fg);
}

.about p {
  margin: 0 0 12px;
  color: var(--fg);
}

.about p:last-child {
  margin-bottom: 0;
}

.about a {
  color: var(--accent);
}

/* toast */
.toast {
  position: fixed;
  bottom: 28px;
  left: 50%;
  transform: translate(-50%, 12px);
  background: #142033;
  color: #fff;
  padding: 12px 20px;
  border-radius: 999px;
  font-weight: 700;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
  opacity: 0;
  transition: opacity 0.25s, transform 0.25s;
  z-index: 50;
}

.toast.show {
  opacity: 1;
  transform: translate(-50%, 0);
}

/* dashboard / admin tables */
.panel {
  width: min(960px, 100%);
  margin: 0 auto;
}

.panel-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin: 16px 0 20px;
}

.toolbar {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.toolbar input {
  max-width: 280px;
}

.table-wrap {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  box-shadow: var(--shadow);
  overflow-x: auto;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

th,
td {
  text-align: left;
  padding: 12px 14px;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}

th {
  color: var(--muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

td.wrap {
  white-space: normal;
  max-width: 280px;
  overflow-wrap: anywhere;
}

td a {
  color: var(--accent);
}

.badge {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 700;
}

.badge.on {
  background: rgba(19, 115, 51, 0.14);
  color: var(--ok);
}

.badge.off {
  background: rgba(180, 35, 24, 0.14);
  color: var(--danger);
}

.row-actions {
  display: flex;
  gap: 6px;
}

.icon-btn {
  border: 1px solid var(--border);
  background: transparent;
  color: var(--fg);
  border-radius: 6px;
  padding: 5px 10px;
  cursor: pointer;
  font-size: 13px;
}

.icon-btn.danger {
  color: var(--danger);
  border-color: var(--danger);
}

.empty {
  padding: 40px;
  text-align: center;
  color: var(--muted);
}

.signin-prompt {
  text-align: center;
  padding: 60px 20px;
  color: var(--muted);
}

/* modal */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  display: grid;
  place-items: center;
  padding: 20px;
  z-index: 60;
}

.modal {
  width: min(440px, 100%);
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
  display: grid;
  gap: 14px;
}

.modal h3 {
  margin: 0;
}

.modal .actions {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
}

/* stats */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 14px;
  margin-bottom: 20px;
}

.stat-card {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--card);
  padding: 16px;
}

.stat-card h4 {
  margin: 0 0 10px;
  font-size: 13px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.bar-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 8px;
  align-items: center;
  margin-bottom: 8px;
  font-size: 13px;
}

.bar {
  height: 10px;
  border-radius: 999px;
  background: var(--accent);
  min-width: 4px;
}

.bar-track {
  background: var(--chip);
  border-radius: 999px;
  overflow: hidden;
}

.big-number {
  font-size: 36px;
  font-weight: 800;
}

/* footer */
.site-footer {
  margin-top: 48px;
  border-top: 1px solid var(--border);
}

.footer-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 24px 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

.footer-brand {
  color: var(--muted);
  font-size: 14px;
}

.footer-links {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}

.footer-links a {
  color: var(--muted);
  text-decoration: none;
  font-size: 14px;
}

.footer-links a:hover {
  color: var(--accent);
}

/* legal pages */
.legal {
  width: min(760px, 100%);
  margin: 0 auto;
  padding: 8px 0 56px;
  line-height: 1.8;
}

.legal h1 {
  font-size: clamp(28px, 5vw, 40px);
  margin: 16px 0 4px;
}

.legal h2 {
  font-size: 20px;
  margin: 32px 0 8px;
}

.legal p,
.legal li {
  color: var(--fg);
}

.legal .legal-meta {
  color: var(--muted);
  font-size: 14px;
  margin-top: 0;
}

.legal ul {
  padding-left: 20px;
}

.legal li {
  margin-bottom: 8px;
}

.legal a {
  color: var(--accent);
}

.legal .legal-back {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

@media (max-width: 640px) {
  .grid,
  .features {
    grid-template-columns: 1fr;
  }

  .result-row {
    grid-template-columns: 1fr;
  }
}