:root {

  --bg-950: #e9f4fb;
  --bg-900: #fff4dd;
  --bg-800: #ffffff;
  --text-100: #123140;
  --text-300: #4b6570;
  --gold-500: #0f7e9b;
  --gold-400: #0b5f77;
  --surface: rgba(255, 255, 255, 0.96);
  --border: #c8dbe3;
  --shadow-lg: 0 12px 24px rgba(12, 54, 68, 0.12);

  --bg-page: radial-gradient(circle at 15% 0%, #1a202c 0%, var(--bg-950) 45%, #050608 100%);
  --surface: rgba(255, 255, 255, 0.96);
  --surface-2: color-mix(in srgb, var(--bg-800) 88%, black 12%);
  --ink: var(--text-100);
  --muted: var(--text-300);
  --gold: var(--gold-500);
  --gold-2: var(--gold-400);
  --arrow: #ff5a4a;
  --phase-accelerating: #d8b767;
  --phase-cruising: #a9b2c3;
  --phase-decelerating: #e18264;
  --phase-stopped: #6f7886;

}

:root {
  --bg-page:
    radial-gradient(1200px 700px at 8% 2%, rgba(19, 143, 176, 0.18), transparent 62%),
    radial-gradient(900px 600px at 92% 98%, rgba(220, 132, 32, 0.18), transparent 66%),
    linear-gradient(165deg, #e9f4fb, #fff4dd);
  --surface: #ffffff;
  --surface-2: #f7fbfe;
  --ink: #123140;
  --muted: #4b6570;
  --gold: #0f7e9b;
  --gold-2: #095f76;
  --arrow: #e74c3c;
  --phase-accelerating: #0f7e9b;
  --phase-cruising: #6f8794;
  --phase-decelerating: #d67b19;
  --phase-stopped: #7b8e95;
  --light-border: #b4d0db;
  --light-panel: #f9fcfe;
  --light-panel-2: #f3f9fc;
  --light-btn-border: #9dbac5;
  --light-btn-bg: #f6fbfd;
  --light-btn-top: #0d839f;
  --light-btn-bottom: #0b5f77;
  --light-btn-text: #ffffff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg-page);
  color: var(--ink);
  font-family: "IBM Plex Sans", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

.app {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0.8rem 1rem 1.2rem;
}

.shell {
  width: 100%;
  margin-inline: auto;
}

.hero {
  position: relative;
  margin-bottom: 0.9rem;
  border: 1px solid var(--light-border);
  border-radius: 14px;
  padding: 1.2rem 1.4rem;
  background: linear-gradient(160deg, #ffffff, #f7fbfd);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 12px;
  border-radius: 14px 0 0 14px;
  background: var(--gold);
}

.hero-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
}

.hero-top > :first-child {
  min-width: 0;
  padding-left: 0.4rem;
}

.kicker {
  margin: 0;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--gold-2);
  font-weight: 700;
}

.hero h1 {
  margin: 0.35rem 0 0;
  font-size: clamp(1.85rem, 2.8vw, 3rem);
  line-height: 1.05;
  color: var(--ink);
}

.subtitle {
  margin: 0.38rem 0 0;
  font-size: 1rem;
  color: var(--muted);
  max-width: 76ch;
}

.top-row {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  margin-bottom: 0.65rem;
}

.status-line {
  margin: 0;
  font-size: clamp(1.25rem, 2.1vw, 1.85rem);
  color: var(--ink);
  flex: 1;
}

.status-line strong {
  color: var(--gold-2);
}

.scene-wrap {
  display: grid;
  grid-template-columns: 1.8fr 1fr;
  gap: 0.8rem;
}

.elevator-box {
  position: relative;
  height: 390px;
  background: linear-gradient(165deg, var(--surface), var(--surface-2));
  border: 3px solid color-mix(in srgb, var(--gold) 55%, #000 45%);
  border-radius: 0.65rem;
  box-shadow: 0 10px 24px rgba(0, 0, 0, 0.35);
}

.floor-thermometer {
  position: absolute;
  left: 0.65rem;
  top: 0.65rem;
  width: 64px;
  z-index: 2;
  text-align: center;
}

.thermo-title {
  font-size: 0.76rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

.thermo-track {
  height: 302px;
  border-radius: 999px;
  border: 2px solid color-mix(in srgb, var(--gold) 55%, #151515 45%);
  background: color-mix(in srgb, var(--bg-900) 80%, #000 20%);
  position: relative;
  overflow: hidden;
}

.thermo-fill {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 0%;
  transition: height 140ms linear, background-color 140ms linear;
}

.thermo-fill.phase-accelerating {
  background: linear-gradient(180deg, color-mix(in srgb, var(--phase-accelerating) 80%, #fff 20%), var(--phase-accelerating));
}

.thermo-fill.phase-cruising {
  background: linear-gradient(180deg, color-mix(in srgb, var(--phase-cruising) 70%, #fff 30%), var(--phase-cruising));
}

.thermo-fill.phase-decelerating {
  background: linear-gradient(180deg, color-mix(in srgb, var(--phase-decelerating) 80%, #fff 20%), var(--phase-decelerating));
}

.thermo-fill.phase-stopped {
  background: linear-gradient(180deg, color-mix(in srgb, var(--phase-stopped) 75%, #fff 25%), var(--phase-stopped));
}

.thermo-floor {
  margin-top: 0.32rem;
  color: var(--gold-2);
  font-weight: 700;
}

.floor-label {
  position: absolute;
  left: 50%;
  top: 0.62rem;
  transform: translateX(-50%);
  font-size: clamp(1.35rem, 2vw, 1.9rem);
  font-weight: 700;
  color: var(--gold-2);
}

.cat-stage {
  position: absolute;
  inset: 0;
}

.bubble {
  position: absolute;
  top: 2.2rem;
  right: 1.7rem;
  width: min(240px, 44%);
  min-height: 78px;
  border: 2px solid color-mix(in srgb, var(--gold) 45%, #111 55%);
  border-radius: 48% 42% 50% 44% / 42% 50% 46% 48%;
  background: #f7f1df;
  display: grid;
  place-items: center;
  text-align: center;
  padding: 0.65rem;
  font-size: clamp(0.9rem, 1.1vw, 1.15rem);
  font-weight: 700;
  color: #e45743;
}

.bubble::before,
.bubble::after {
  content: "";
  position: absolute;
  border: 2px solid color-mix(in srgb, var(--gold) 45%, #111 55%);
  background: #f7f1df;
  border-radius: 50%;
}

.bubble::before {
  width: 24px;
  height: 19px;
  left: -18px;
  bottom: -20px;
}

.bubble::after {
  width: 14px;
  height: 11px;
  left: -33px;
  bottom: -37px;
}

.cat {
  position: absolute;
  left: 50%;
  bottom: 0.45rem;
  transform: translateX(-50%);
  width: 138px;
}

.cat-ear {
  position: absolute;
  width: 54px;
  height: 54px;
  top: -20px;
  background: #111;
  border: 2px solid #050505;
  clip-path: polygon(50% 0%, 0% 100%, 100% 100%);
}

.cat-ear-left {
  left: 10px;
  transform: rotate(-10deg);
}

.cat-ear-right {
  right: 10px;
  transform: rotate(10deg);
}

.cat-face {
  width: 138px;
  height: 103px;
  border-radius: 62px 62px 58px 58px;
  background: linear-gradient(180deg, #f7f7f7, #dddddd);
  border: 2px solid #2c2c2c;
  position: relative;
  box-shadow: inset 0 -7px 0 rgba(0, 0, 0, 0.09);
}

.cat-patch {
  position: absolute;
  background: #111;
  border-radius: 50%;
  opacity: 0.9;
}

.cat-patch-left {
  width: 45px;
  height: 34px;
  left: 14px;
  top: 15px;
  transform: rotate(-14deg);
}

.cat-patch-right {
  width: 30px;
  height: 24px;
  right: 22px;
  top: 23px;
}

.cat-eye {
  position: absolute;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  top: 42px;
  background: #1d8f46;
  border: 1px solid #0f0f0f;
}

.cat-eye-left {
  left: 45px;
}

.cat-eye-right {
  right: 45px;
}

.cat-nose {
  position: absolute;
  width: 18px;
  height: 12px;
  left: 61px;
  top: 58px;
  background: #d47f8f;
  clip-path: polygon(50% 100%, 0% 0%, 100% 0%);
}

.cat-mouth {
  position: absolute;
  width: 24px;
  height: 14px;
  left: 58px;
  top: 69px;
  border-bottom: 2px solid #202020;
  border-radius: 0 0 50% 50%;
}

.fbd-panel {
  background: linear-gradient(165deg, var(--surface), var(--surface-2));
  border: 3px solid color-mix(in srgb, var(--gold) 55%, #000 45%);
  border-radius: 0.65rem;
  padding: 0.65rem;
}

.fbd-panel h2 {
  font-size: clamp(1.25rem, 2vw, 1.8rem);
  margin: 0 0 0.65rem;
  color: var(--gold-2);
}

.fbd-stage {
  position: relative;
  height: 312px;
}

.fbd-cat {
  position: absolute;
  left: 28%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 72px;
  height: 72px;
  border-radius: 50%;
  background: #ececec;
  border: 2px solid #2d2d2d;
}

.fbd-cat-face {
  position: absolute;
  inset: 22px 20px;
  border-radius: 50%;
  background: #171717;
}

.fbd-arrow {
  position: absolute;
  left: 28%;
  width: 8px;
  transform: translateX(-50%);
  border-radius: 4px;
  background: var(--arrow);
}

.fbd-arrow span {
  position: absolute;
  left: 14px;
  width: max-content;
  font-family: "IBM Plex Sans", "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: clamp(1.05rem, 1.35vw, 1.45rem);
  color: var(--arrow);
  font-weight: 700;
}

.fbd-arrow.up {
  bottom: 50%;
  height: 118px;
}

.fbd-arrow.up::before {
  content: "";
  position: absolute;
  left: -10px;
  top: -14px;
  border-left: 14px solid transparent;
  border-right: 14px solid transparent;
  border-bottom: 16px solid var(--arrow);
}

.fbd-arrow.up span {
  top: 4px;
}

.fbd-arrow.down {
  top: 50%;
  height: 118px;
}

.fbd-arrow.down::before {
  content: "";
  position: absolute;
  left: -10px;
  bottom: -14px;
  border-left: 14px solid transparent;
  border-right: 14px solid transparent;
  border-top: 16px solid var(--arrow);
}

.fbd-arrow.down span {
  bottom: 4px;
}

.congruency-mark {
  display: none;
  position: absolute;
  left: -8px;
  width: 24px;
  height: 4px;
  border-radius: 999px;
  background: #fff;
}

.fbd-arrow.up .congruency-mark {
  top: calc(50% - 2px);
}

.fbd-arrow.down .congruency-mark {
  top: calc(50% - 2px);
}

.fbd-arrow.equal .congruency-mark {
  display: block;
}

.fbd-arrow.larger {
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--gold) 55%, #000 45%);
}

.accel-indicator-title {
  margin: 0;
  color: var(--muted);
  font-size: 0.84rem;
  font-weight: 700;
  line-height: 1.1;
}

.accel-arrow {
  position: relative;
  width: 42px;
  height: 165px;
  margin: 0 auto;
}

.accel-shaft {
  position: absolute;
  top: 12px;
  bottom: 12px;
  width: 4px;
  border-radius: 999px;
  background: color-mix(in srgb, var(--gold) 58%, #222 42%);
}

.accel-shaft-left {
  left: calc(50% - 6px);
}

.accel-shaft-right {
  left: calc(50% + 2px);
}

.accel-head {
  position: absolute;
  width: 0;
  height: 0;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
}

.accel-head-up-left {
  left: calc(50% - 10px);
  top: 0;
  border-bottom: 11px solid transparent;
}

.accel-head-up-right {
  left: calc(50% - 2px);
  top: 0;
  border-bottom: 11px solid transparent;
}

.accel-head-down-left {
  left: calc(50% - 10px);
  bottom: 0;
  border-top: 11px solid transparent;
}

.accel-head-down-right {
  left: calc(50% - 2px);
  bottom: 0;
  border-top: 11px solid transparent;
}

.accel-marker {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 26px;
  height: 26px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-weight: 700;
  font-size: 1rem;
  color: #121212;
  background: var(--phase-stopped);
  border: 1px solid rgba(0, 0, 0, 0.35);
  transition: top 160ms ease, background-color 160ms linear;
}

.accel-double-mark {
  display: none;
}

.accel-arrow.accel-up .accel-marker {
  top: 16%;
  background: var(--phase-accelerating);
}

.accel-arrow.accel-down .accel-marker {
  top: 84%;
  background: var(--phase-decelerating);
}

.accel-arrow.accel-none .accel-marker {
  top: 50%;
  background: var(--phase-stopped);
}

.accel-arrow.accel-up .accel-head-up-left,
.accel-arrow.accel-up .accel-head-up-right {
  border-bottom-color: var(--phase-accelerating);
}

.accel-arrow.accel-down .accel-head-down-left,
.accel-arrow.accel-down .accel-head-down-right {
  border-top-color: var(--phase-decelerating);
}

.accel-arrow.accel-up .accel-head-down-left,
.accel-arrow.accel-up .accel-head-down-right {
  border-top-color: transparent;
}

.accel-arrow.accel-down .accel-head-up-left,
.accel-arrow.accel-down .accel-head-up-right {
  border-bottom-color: transparent;
}

.accel-arrow.accel-none .accel-head-up-left,
.accel-arrow.accel-none .accel-head-up-right,
.accel-arrow.accel-none .accel-head-down-left,
.accel-arrow.accel-none .accel-head-down-right {
  border-top-color: transparent;
  border-bottom-color: transparent;
}

.accel-direction {
  margin: 0.1rem 0 0;
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.02em;
}

.accel-direction.dir-up {
  color: var(--phase-accelerating);
}

.accel-direction.dir-down {
  color: var(--phase-decelerating);
}

.accel-direction.dir-none {
  color: var(--phase-stopped);
}

.meta {
  margin-top: 0.55rem;
  display: grid;
  gap: 0.65rem;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.meta-chip {
  border: 2px solid color-mix(in srgb, var(--gold) 45%, transparent 55%);
  background: color-mix(in srgb, var(--surface-2) 84%, #000 16%);
  border-radius: 0.5rem;
  padding: 0.45rem 0.62rem;
  color: var(--muted);
  font-size: 1.04rem;
}

.meta-chip-strong {
  font-size: 1.24rem;
  font-weight: 700;
  color: var(--ink);
  border-color: color-mix(in srgb, var(--gold-2) 70%, transparent 30%);
}

#accel-line,
#compare-line {
  color: var(--gold-2);
  font-size: 1.35rem;
  font-weight: 800;
  background: color-mix(in srgb, var(--surface) 86%, transparent 14%);
}

.controls {
  margin-top: 0.55rem;
  display: grid;
  gap: 0.8rem;
}

.sim-speed-control {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.55rem 0.8rem;
}

.sim-speed-control label {
  color: var(--muted);
  font-size: 1rem;
}

.sim-speed-control input[type="range"] {
  width: min(280px, 60vw);
  accent-color: var(--gold);
}

.sim-speed-control output {
  color: var(--gold-2);
  font-size: 1rem;
  font-weight: 700;
  min-width: 3.8rem;
}

.elevator-accel {
  position: absolute;
  left: 74px;
  top: 44px;
  z-index: 3;
  width: 56px;
  text-align: center;
}

.control-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
}

.controls button {
  border-radius: 10px;
  background: linear-gradient(160deg, #0d839f, #0b5f77);
  color: #ffffff;
  font-weight: 700;
  border: 1px solid #0a5d74;
  padding: 0.58rem 0.82rem;
  cursor: pointer;
}

.elevator-box,
.fbd-panel,
.study-panel {
  border-color: var(--light-border);
  background: linear-gradient(165deg, var(--light-panel), var(--light-panel-2));
  box-shadow: 0 10px 20px rgba(12, 54, 68, 0.12);
}

.fbd-arrow.larger {
  box-shadow: 0 0 0 3px rgba(15, 126, 155, 0.3);
}

.thermo-track {
  background: #f9fcff;
  border-color: var(--light-border);
}

.meta-chip {
  border-color: #c6dde6;
  background: #f7fcff;
  color: #4b6570;
}

#accel-line,
#compare-line {
  color: #0b5f77;
  background: #eef7fb;
  border-color: #b8d1db;
}

.controls button {
  border-radius: 10px;
  background: linear-gradient(160deg, #0d839f, #0b5f77);
  color: #ffffff;
  font-weight: 700;
  border: 1px solid #0a5d74;
  padding: 0.58rem 0.82rem;
  cursor: pointer;
}

.controls button:hover {
  border-color: #0f7e9b;
}

.control-buttons button:first-child,
.control-buttons button:nth-child(2),
.control-buttons button:nth-child(3) {
  background: linear-gradient(160deg, var(--light-btn-top), var(--light-btn-bottom));
  color: var(--light-btn-text);
  border-color: #0a5d74;
}

.study-card {
  border-color: #bed6de;
  background: #f9fcff;
}

.physics-explain {
  color: #123140;
}

.direction-note,
.rule-list,
.prompt-list {
  color: #294a57;
}

.controls button:hover {
  border-color: var(--gold-2);
}

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

.study-panel {
  margin-top: 0.6rem;
  border: 2px solid color-mix(in srgb, var(--gold) 48%, transparent 52%);
  border-radius: 0.6rem;
  background: linear-gradient(165deg, color-mix(in srgb, var(--surface) 88%, #000 12%), color-mix(in srgb, var(--surface-2) 84%, #000 16%));
  padding: 0.6rem 0.7rem 0.7rem;
}

.study-panel h2 {
  margin: 0;
  font-size: clamp(1.15rem, 1.7vw, 1.45rem);
  color: var(--gold-2);
}

.physics-explain,
.direction-note {
  margin: 0.35rem 0 0;
  color: var(--text-300);
  font-size: 0.96rem;
}

.physics-explain {
  color: var(--text-100);
  font-weight: 700;
}

.study-columns {
  margin-top: 0.55rem;
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 0.6rem;
}

.study-card {
  border: 1px solid color-mix(in srgb, var(--gold) 35%, transparent 65%);
  border-radius: 0.48rem;
  padding: 0.5rem 0.6rem;
  background: color-mix(in srgb, var(--surface-2) 78%, #000 22%);
}

.study-card h3 {
  margin: 0 0 0.35rem;
  color: var(--gold-2);
  font-size: 1.04rem;
}

.rule-list,
.prompt-list {
  margin: 0;
  padding-left: 1.2rem;
  color: var(--text-300);
  font-size: 0.92rem;
  line-height: 1.3;
}

.rule-list li + li,
.prompt-list li + li {
  margin-top: 0.2rem;
}

.attribution {
  margin-top: 0.9rem;
  color: var(--muted);
  font-size: 0.95rem;
}

@media (max-width: 980px) {
  .scene-wrap {
    grid-template-columns: 1fr;
  }

  .fbd-stage {
    height: 360px;
  }

  .elevator-box {
    height: 392px;
  }

  .controls button {
  border-radius: 10px;
  background: linear-gradient(160deg, #0d839f, #0b5f77);
  color: #ffffff;
  font-weight: 700;
  border: 1px solid #0a5d74;
  padding: 0.58rem 0.82rem;
  cursor: pointer;
}

  .thermo-track {
    height: 305px;
  }

  .meta {
    grid-template-columns: 1fr;
  }

  .study-columns {
    grid-template-columns: 1fr;
  }

  .top-row {
    flex-direction: column;
    align-items: flex-start;
  }

  .elevator-accel {
    top: 40px;
    left: 72px;
  }
}