:root {
  --bg: #f4f7fb;
  --ink: #172033;
  --muted: #657287;
  --line: #d6deea;
  --panel: #ffffff;
  --blue: #2357a6;
  --cyan: #17a2b8;
  --gold: #f0b429;
  --green: #1b9a59;
  --red: #d94a4a;
  --yellow: #f5d04c;
  --shadow: 0 16px 36px rgba(23, 32, 51, .10);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background:
    radial-gradient(circle at 12% 8%, rgba(23,162,184,.16), transparent 30%),
    radial-gradient(circle at 84% 12%, rgba(240,180,41,.18), transparent 28%),
    linear-gradient(180deg, #eef5ff 0%, #f8fbff 100%);
  color: var(--ink);
  font-family: "Noto Sans TC", system-ui, -apple-system, sans-serif;
}

body.modal-open {
  overflow: hidden;
}

button, input { font: inherit; }

button {
  min-height: 34px;
  border: 1px solid #c3cede;
  background: #fff;
  color: var(--ink);
  border-radius: 8px;
  padding: 6px 10px;
  font-weight: 700;
  cursor: pointer;
}

button:hover { border-color: var(--blue); }
button.danger { color: #9f2d2d; }
button.primary {
  background: var(--blue);
  border-color: var(--blue);
  color: white;
}

input {
  min-height: 34px;
  border: 1px solid #c3cede;
  border-radius: 8px;
  padding: 6px 9px;
}

.app {
  width: min(1240px, calc(100% - 16px));
  margin: 0 auto;
  padding: 6px 0 10px;
}

.topbar {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 8px;
}

.player-row {
  display: grid;
  grid-template-columns: auto 120px auto auto minmax(120px, 1fr);
  align-items: center;
  gap: 6px;
  margin-bottom: 6px;
  color: var(--muted);
  font-size: .82rem;
}

.player-row label,
.player-row span {
  font-weight: 700;
}

.home-login-card {
  margin: 0;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}

.back-link {
  color: var(--blue);
  text-decoration: none;
  font-weight: 800;
}

.brand {
  font-size: 1.05rem;
  font-weight: 900;
}

.brand-sub {
  color: var(--muted);
  font-size: .8rem;
}

.home-screen {
  display: grid;
  gap: 12px;
}

.home-hero {
  min-height: 270px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 360px;
  gap: 18px;
  align-items: center;
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background:
    linear-gradient(135deg, rgba(255,255,255,.96), rgba(232,244,255,.94)),
    repeating-linear-gradient(30deg, rgba(35,87,166,.06) 0 1px, transparent 1px 30px);
  box-shadow: var(--shadow);
  overflow: hidden;
}

.home-hero h1 {
  font-size: clamp(2.4rem, 6vw, 4.6rem);
  line-height: .98;
  margin: 0 0 12px;
}

.home-hero p:last-child {
  margin: 0;
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.7;
  max-width: 620px;
}

.home-cubes {
  position: relative;
  height: 260px;
}

.home-cubes span {
  position: absolute;
  width: 74px;
  height: 74px;
  left: calc(136px + (var(--x) - var(--y)) * 36px);
  top: calc(138px + (var(--x) + var(--y)) * 20px - var(--z) * 44px);
  transform: rotate(45deg) skew(-12deg, -12deg);
  border-radius: 8px;
  background: linear-gradient(145deg, #7dd3e1, #2357a6);
  border: 2px solid rgba(23,32,51,.18);
  box-shadow: 10px 12px 0 rgba(23,87,166,.20);
}

.home-actions {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
}

.home-actions.teacher-mode {
  grid-template-columns: repeat(5, minmax(0, 1fr));
}

.home-card {
  min-height: 128px;
  display: grid;
  grid-template-columns: 58px minmax(0, 1fr);
  grid-template-rows: auto auto auto;
  align-content: center;
  column-gap: 14px;
  text-align: left;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.home-card span {
  grid-row: 1 / 4;
  font-size: 2.3rem;
}

.home-card b {
  font-size: 1.25rem;
}

.home-card small {
  color: var(--muted);
  font-size: .92rem;
}

.home-card em {
  width: fit-content;
  margin-top: 8px;
  padding: 3px 8px;
  border-radius: 999px;
  background: #eef5ff;
  color: var(--blue);
  font-size: .76rem;
  font-style: normal;
  font-weight: 900;
}

.primary-card {
  background: linear-gradient(135deg, #2357a6, #17a2b8);
  color: #fff;
  border-color: transparent;
}

.primary-card small { color: rgba(255,255,255,.82); }
.primary-card em {
  background: rgba(255,255,255,.18);
  color: #fff;
}

.home-card.locked-card {
  background: #f5f7fb;
  color: #6b7482;
  border-color: #d5dde9;
}

.home-card.locked-card span,
.home-card.locked-card small {
  color: #7c8796;
}

.home-card.locked-card em {
  background: #fff3d6;
  color: #8a6400;
}

.teacher-card {
  background: linear-gradient(135deg, #172033, #2357a6);
  color: #fff;
  border-color: transparent;
}

.teacher-card small { color: rgba(255,255,255,.78); }
.teacher-card em {
  background: rgba(255,255,255,.16);
  color: #fff;
}

.home-qr-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 132px;
  gap: 18px;
  align-items: center;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}

.home-qr-card b {
  color: var(--blue);
  font-size: 1.08rem;
}

.home-qr-card p {
  margin: 5px 0;
  color: var(--muted);
}

.home-qr-card code {
  color: var(--muted);
  word-break: break-all;
}

.home-qr-box {
  width: 132px;
  height: 132px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.home-qr-box canvas {
  width: 112px;
  height: 112px;
  image-rendering: pixelated;
}

.play-header {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 8px;
  align-items: stretch;
  margin-bottom: 6px;
}

.play-header, .status-panel, .view-panel, .builder-panel, .reference, .solid-preview-panel, .summary-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.play-header {
  padding: 8px 10px;
}

.eyebrow {
  margin: 0 0 3px;
  color: var(--cyan);
  font-weight: 900;
}

h1 {
  margin: 0;
  font-size: clamp(1.05rem, 2.2vw, 1.55rem);
  line-height: 1.1;
  letter-spacing: 0;
}

.status-panel {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  padding: 8px;
  gap: 6px;
  box-shadow: none;
}

.status-panel div {
  display: block;
  border-bottom: 0;
  padding-bottom: 0;
}

.status-panel div:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.status-panel span {
  color: var(--muted);
  font-weight: 700;
  font-size: .8rem;
}

.status-panel strong {
  display: block;
  font-size: 1.05rem;
  color: var(--blue);
}

.toolbar {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 6px;
  margin-top: 8px;
  margin-bottom: 0;
}

.score-strip {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
  margin-top: 6px;
  color: var(--muted);
  font-size: .78rem;
}

.score-strip span {
  padding: 4px 6px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #f8fbff;
}

.score-strip b { color: var(--blue); }

.workspace {
  display: grid;
  grid-template-columns: 190px minmax(300px, 1fr) 190px;
  gap: 8px;
  align-items: start;
}

.intro-workspace {
  display: grid;
  grid-template-columns: 360px minmax(0, 1fr);
  gap: 10px;
  align-items: start;
}

.race-lobby-grid {
  display: grid;
  grid-template-columns: 340px minmax(0, 1fr);
  gap: 10px;
  align-items: start;
}

.race-join-row {
  display: grid;
  grid-template-columns: 140px auto;
  gap: 8px;
  align-items: center;
}

.race-qr-box {
  width: 156px;
  height: 156px;
  margin-top: 10px;
}

.race-qr-box canvas {
  width: 136px;
  height: 136px;
}

.race-url {
  display: block;
  margin-top: 8px;
  color: var(--muted);
  word-break: break-all;
}

.race-hud {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-bottom: 6px;
}

.race-hud div {
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  box-shadow: var(--shadow);
}

.race-hud span {
  display: block;
  color: var(--muted);
  font-size: .76rem;
  font-weight: 800;
}

.race-hud b {
  color: var(--blue);
  font-size: 1rem;
}

.intro-solid {
  min-height: 250px;
  touch-action: none;
}

.intro-solid svg {
  width: min(100%, 320px);
}

.draggable-cubes {
  cursor: grab;
  transform-box: fill-box;
  transition: transform 220ms ease, opacity 160ms ease;
}

.draggable-cubes.dragging {
  cursor: grabbing;
  opacity: .82;
  transition: none;
}

.intro-answer-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(120px, 1fr));
  gap: 10px;
}

.intro-answer-card h3 {
  margin: 0 0 6px;
  color: var(--blue);
}

.intro-view-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 5px;
}

.intro-cell {
  aspect-ratio: 1;
  border: 1px solid #c4cede;
  border-radius: 6px;
  background: #eef3f9;
  cursor: pointer;
}

.intro-cell.selected {
  background: #244c8f;
  border-color: #1c3c72;
}

.intro-cell.ok {
  background: var(--green);
}

.intro-cell.extra {
  background: var(--red);
}

.intro-cell.missing {
  background: var(--yellow);
}

.intro-toolbar {
  grid-template-columns: repeat(4, 1fr);
}

.view-panel, .builder-panel, .reference, .solid-preview-panel {
  padding: 7px;
}

.panel-title {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 5px;
}

.panel-title h2 {
  margin: 0;
  font-size: .9rem;
}

.panel-title span {
  color: var(--muted);
  font-size: .68rem;
  text-align: right;
}

.views-grid {
  display: grid;
  gap: 4px;
}

.view-card h3 {
  margin: 0 0 2px;
  font-size: .74rem;
}

.view-grid, .build-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 3px;
}

.view-cell, .build-cell {
  aspect-ratio: 1;
  border: 1px solid #c4cede;
  border-radius: 4px;
  background: #eef3f9;
}

.view-grid {
  width: 126px;
}

.view-cell.filled {
  background: #244c8f;
  border-color: #1c3c72;
}

.view-cell.ok {
  background: var(--green);
  border-color: #137141;
}

.view-cell.extra {
  background: var(--red);
  border-color: #a93232;
}

.view-cell.missing {
  background: var(--yellow);
  border-color: #bd9220;
}

.layer-tabs {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
  margin-bottom: 6px;
}

.layer-tab.active {
  background: var(--blue);
  border-color: var(--blue);
  color: white;
}

.build-grid {
  width: min(100%, 285px);
  margin: 0 auto;
  gap: 6px;
}

.build-cell {
  position: relative;
  min-width: 0;
  background: linear-gradient(145deg, #f7fbff, #dce7f4);
}

.build-cell.on {
  background: linear-gradient(145deg, #35b5c8, #2357a6);
  border-color: #18437f;
  box-shadow: inset 0 0 0 2px rgba(255,255,255,.35);
}

.build-cell.ghost {
  background:
    repeating-linear-gradient(135deg, rgba(35, 87, 166, .18) 0 6px, rgba(35, 87, 166, .08) 6px 12px),
    #f7fbff;
  border-color: rgba(35, 87, 166, .28);
}

.build-cell.blocked {
  cursor: not-allowed;
  background:
    linear-gradient(145deg, rgba(217,74,74,.10), rgba(217,74,74,.04)),
    #f8fbff;
}

.build-cell.hint {
  outline: 4px solid var(--gold);
  outline-offset: -4px;
}

.build-cell::after {
  content: attr(data-pos);
  position: absolute;
  left: 6px;
  bottom: 4px;
  color: rgba(23, 32, 51, .45);
  font-size: .65rem;
  font-weight: 700;
}

.build-cell.on::after { color: rgba(255,255,255,.78); }

.feedback {
  min-height: 36px;
  margin-top: 8px;
  padding: 7px 9px;
  border-radius: 8px;
  background: #eef5ff;
  color: #24415f;
  line-height: 1.28;
  font-size: .9rem;
}

.feedback.success {
  background: #e8f8ef;
  color: #12623a;
}

.hidden { display: none !important; }

.solid-preview-panel {
  position: fixed;
  right: 12px;
  bottom: 12px;
  z-index: 5;
  width: min(460px, calc(100% - 24px));
  margin: 0;
  pointer-events: none;
}

.solid-preview-wrap {
  display: grid;
  grid-template-columns: 150px minmax(0, 1fr);
  gap: 8px;
  align-items: center;
}

.solid-preview {
  min-height: 96px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background:
    linear-gradient(180deg, rgba(255,255,255,.86), rgba(238,245,255,.9)),
    repeating-linear-gradient(30deg, rgba(35,87,166,.08) 0 1px, transparent 1px 28px);
  display: grid;
  place-items: center;
  overflow: hidden;
}

.solid-preview svg {
  width: min(100%, 150px);
  height: auto;
  display: block;
}

.cube-face {
  stroke: rgba(23, 32, 51, .28);
  stroke-width: 1.5;
  stroke-linejoin: round;
}

.floor-grid {
  fill: rgba(255,255,255,.45);
  stroke: rgba(23, 32, 51, .32);
  stroke-width: 1.2;
  stroke-linejoin: round;
}

.floor-axis {
  stroke: rgba(35, 87, 166, .68);
  stroke-width: 2;
  stroke-linecap: round;
}

.cube-top { fill: #7dd3e1; }
.cube-left { fill: #2357a6; }
.cube-right { fill: #17a2b8; }

.solid-note {
  color: var(--muted);
  line-height: 1.35;
}

.solid-note b {
  display: block;
  color: var(--blue);
  font-size: 1.05rem;
  margin-bottom: 4px;
}

.solid-note p { margin: 0; }

.advance-bar {
  height: 5px;
  margin-top: 8px;
  border-radius: 999px;
  background: #dce7f4;
  overflow: hidden;
}

.advance-bar::before {
  content: "";
  display: block;
  height: 100%;
  width: 100%;
  background: var(--green);
  transform-origin: left center;
  animation: advance-countdown 1400ms linear forwards;
}

@keyframes advance-countdown {
  from { transform: scaleX(1); }
  to { transform: scaleX(0); }
}

.summary-panel {
  position: fixed;
  inset: 0;
  z-index: 10;
  display: grid;
  place-items: center;
  padding: 18px;
  background: rgba(23, 32, 51, .42);
  overscroll-behavior: contain;
}

.summary-card {
  width: min(420px, 100%);
  padding: 18px;
}

.summary-card h2 {
  margin: 0 0 12px;
}

.summary-stats {
  display: grid;
  gap: 8px;
  margin-bottom: 14px;
}

.summary-stats div {
  display: flex;
  justify-content: space-between;
  border-bottom: 1px solid var(--line);
  padding-bottom: 6px;
}

.upload-status {
  min-height: 26px;
  margin: 8px 0;
  color: var(--muted);
  font-size: .9rem;
}

.leaderboard-card {
  width: min(720px, 100%);
  max-height: min(680px, calc(100dvh - 28px));
  display: flex;
  flex-direction: column;
  overflow: hidden;
  contain: layout paint;
}

.teacher-dashboard-card {
  width: min(980px, 100%);
  max-height: min(760px, calc(100vh - 28px));
  overflow: auto;
}

.teacher-dashboard-head {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  align-items: flex-start;
}

.teacher-dashboard-head h2 {
  margin: 0;
}

.teacher-controls {
  display: grid;
  grid-template-columns: auto 120px auto minmax(0, 1fr);
  gap: 8px;
  align-items: center;
  margin: 8px 0 12px;
}

.teacher-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin: 10px 0 12px;
}

.teacher-stat {
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #f8fbff;
}

.teacher-stat span {
  display: block;
  color: var(--muted);
  font-size: .78rem;
  font-weight: 800;
}

.teacher-stat b {
  color: var(--blue);
  font-size: 1.4rem;
}

.teacher-table-wrap {
  overflow-x: auto;
}

.teacher-table {
  min-width: 860px;
}

.teacher-table .ok {
  color: var(--green);
  font-weight: 900;
}

.teacher-table .pending {
  color: var(--muted);
  font-weight: 800;
}

.leaderboard-table {
  width: 100%;
  border-collapse: collapse;
  font-size: .9rem;
}

.leaderboard-table-wrap {
  flex: 1 1 auto;
  min-height: 0;
  max-height: min(500px, calc(100dvh - 210px));
  overflow: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior: contain;
  touch-action: pan-y;
  border: 1px solid var(--line);
  border-radius: 8px;
  margin-bottom: 12px;
  background: #fff;
}

.leaderboard-table th,
.leaderboard-table td {
  border-bottom: 1px solid var(--line);
  padding: 8px 6px;
  text-align: left;
  background: #fff;
}

.leaderboard-table th {
  position: sticky;
  top: 0;
  z-index: 1;
  color: var(--muted);
  font-size: .78rem;
  background: #f8fbff;
}

.quick-help {
  margin-top: 6px;
  padding-top: 6px;
  border-top: 1px solid var(--line);
}

.quick-help b {
  color: var(--blue);
  font-size: .76rem;
}

.quick-help p {
  margin: 0;
  color: var(--muted);
  font-size: .7rem;
  line-height: 1.25;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 14px;
  color: var(--muted);
  font-weight: 700;
}

.dot {
  display: inline-block;
  width: 14px;
  height: 14px;
  border-radius: 4px;
  margin-right: 5px;
  vertical-align: -2px;
}

.dot.target { background: #244c8f; }
.dot.ok { background: var(--green); }
.dot.extra { background: var(--red); }
.dot.missing { background: var(--yellow); }

@media (max-width: 980px) {
  .play-header, .workspace {
    grid-template-columns: 1fr;
  }

  .home-hero,
  .home-actions,
  .home-actions.teacher-mode,
  .home-qr-card,
  .intro-workspace,
  .race-lobby-grid,
  .race-hud {
    grid-template-columns: 1fr;
  }

  .intro-answer-grid {
    grid-template-columns: 1fr;
  }

  .home-cubes {
    height: 190px;
  }

  .panel-title span {
    text-align: left;
  }
}

@media (max-width: 620px) {
  .app {
    width: min(100% - 18px, 1180px);
    padding-top: 8px;
  }

  .topbar {
    display: block;
  }

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

  .solid-preview-wrap {
    grid-template-columns: 1fr;
  }

  .back-link {
    display: inline-block;
    margin-bottom: 8px;
  }

  .play-header {
    padding: 12px;
  }

  .status-panel {
    grid-template-columns: 1fr;
  }

  .teacher-controls,
  .teacher-stats,
  .race-join-row {
    grid-template-columns: 1fr;
  }

  .toolbar {
    display: grid;
    grid-template-columns: 1fr 1fr;
  }

  .view-panel, .builder-panel, .reference {
    padding: 12px;
  }
}