:root {
  color-scheme: light;
  --paper: #f6f7f2;
  --bg-gradient: radial-gradient(ellipse at 75% 48%, #f1f4e9 0, transparent 40%), #f6f7f2;
  --white: #ffffff;
  --card-bg: #ffffff;
  --card-border: #e9ece5;
  --card-hover-border: #dce5d6;
  --panel-bg: #fbfcf9;
  --subtle-bg: #fafbf8;
  --ink: #232921;
  --muted: #747b71;
  --muted-light: #949a8f;
  --line: #e9ece4;
  --green: #3d764a;
  --green-glow: rgba(61, 118, 74, 0.22);
  --green-dark: #295333;
  --green-pale: #edf4ec;
  --accent-gold: #e5a741;
  --cube-white: #f5f2df;
  --cube-yellow: #f2c34e;
  --cube-green: #69a766;
  --cube-blue: #638fcc;
  --cube-orange: #ed9250;
  --cube-red: #de6652;
  --shadow-sm: 0 4px 12px rgba(35, 41, 33, 0.04);
  --shadow-md: 0 10px 28px rgba(35, 41, 33, 0.08);
  --shadow-lg: 0 20px 48px rgba(35, 41, 33, 0.12);
  --mono: "DM Mono", monospace;
  --sans: "DM Sans", sans-serif;
  --display: "Manrope", sans-serif;
  --glow-color: rgba(94, 163, 91, 0.16);
  --particle-color: rgba(94, 163, 91, 0.14);
}

/* Midnight Aurora Theme */
[data-theme="midnight"] {
  color-scheme: dark;
  --paper: #0b0f19;
  --bg-gradient: radial-gradient(ellipse at 75% 30%, #17253d 0, transparent 55%), radial-gradient(circle at 20% 80%, #102a24 0, transparent 45%), #0b0f19;
  --white: #131b2e;
  --card-bg: rgba(19, 27, 46, 0.75);
  --card-border: rgba(56, 189, 248, 0.16);
  --card-hover-border: rgba(0, 245, 155, 0.4);
  --panel-bg: rgba(15, 23, 42, 0.85);
  --subtle-bg: rgba(22, 33, 56, 0.6);
  --ink: #f1f5f9;
  --muted: #94a3b8;
  --muted-light: #64748b;
  --line: rgba(255, 255, 255, 0.08);
  --green: #00f59b;
  --green-glow: rgba(0, 245, 155, 0.35);
  --green-dark: #00c97e;
  --green-pale: rgba(0, 245, 155, 0.12);
  --accent-gold: #f59e0b;
  --cube-white: #ffffff;
  --cube-yellow: #fbbf24;
  --cube-green: #10b981;
  --cube-blue: #38bdf8;
  --cube-orange: #fb923c;
  --cube-red: #f43f5e;
  --shadow-sm: 0 4px 16px rgba(0, 0, 0, 0.4);
  --shadow-md: 0 12px 32px rgba(0, 0, 0, 0.6);
  --shadow-lg: 0 24px 60px rgba(0, 0, 0, 0.8);
  --glow-color: rgba(0, 245, 155, 0.2);
  --particle-color: rgba(56, 189, 248, 0.22);
}

/* Sunset Prism Theme */
[data-theme="sunset"] {
  color-scheme: dark;
  --paper: #16121f;
  --bg-gradient: radial-gradient(ellipse at 80% 25%, #3d1b33 0, transparent 50%), radial-gradient(circle at 15% 75%, #3a2216 0, transparent 45%), #16121f;
  --white: #201a2c;
  --card-bg: rgba(32, 26, 44, 0.8);
  --card-border: rgba(255, 159, 67, 0.2);
  --card-hover-border: rgba(255, 107, 107, 0.45);
  --panel-bg: rgba(26, 21, 37, 0.9);
  --subtle-bg: rgba(40, 32, 54, 0.6);
  --ink: #fceddb;
  --muted: #b8a9c4;
  --muted-light: #897899;
  --line: rgba(255, 255, 255, 0.09);
  --green: #ff9f43;
  --green-glow: rgba(255, 159, 67, 0.35);
  --green-dark: #ee5253;
  --green-pale: rgba(255, 159, 67, 0.15);
  --accent-gold: #fed330;
  --cube-white: #fffdfa;
  --cube-yellow: #feca57;
  --cube-green: #1dd1a1;
  --cube-blue: #54a0ff;
  --cube-orange: #ff9f43;
  --cube-red: #ff6b6b;
  --shadow-sm: 0 4px 16px rgba(18, 12, 28, 0.5);
  --shadow-md: 0 12px 36px rgba(18, 12, 28, 0.7);
  --shadow-lg: 0 24px 64px rgba(18, 12, 28, 0.9);
  --glow-color: rgba(255, 159, 67, 0.22);
  --particle-color: rgba(254, 211, 48, 0.18);
}

/* Cyber Matrix Theme */
[data-theme="cyber"] {
  color-scheme: dark;
  --paper: #070b14;
  --bg-gradient: radial-gradient(ellipse at 70% 30%, #0d2238 0, transparent 50%), radial-gradient(circle at 20% 70%, #15102d 0, transparent 40%), #070b14;
  --white: #0c1424;
  --card-bg: rgba(12, 20, 36, 0.82);
  --card-border: rgba(0, 240, 255, 0.22);
  --card-hover-border: rgba(0, 240, 255, 0.6);
  --panel-bg: rgba(9, 16, 30, 0.92);
  --subtle-bg: rgba(16, 28, 48, 0.65);
  --ink: #e0f2fe;
  --muted: #7dd3fc;
  --muted-light: #38bdf8;
  --line: rgba(0, 240, 255, 0.12);
  --green: #00f0ff;
  --green-glow: rgba(0, 240, 255, 0.4);
  --green-dark: #0284c7;
  --green-pale: rgba(0, 240, 255, 0.14);
  --accent-gold: #f43f5e;
  --cube-white: #ffffff;
  --cube-yellow: #facc15;
  --cube-green: #22c55e;
  --cube-blue: #00f0ff;
  --cube-orange: #fb923c;
  --cube-red: #ff0055;
  --shadow-sm: 0 4px 16px rgba(0, 0, 0, 0.5);
  --shadow-md: 0 12px 36px rgba(0, 0, 0, 0.75);
  --shadow-lg: 0 24px 64px rgba(0, 240, 255, 0.15);
  --glow-color: rgba(0, 240, 255, 0.22);
  --particle-color: rgba(0, 240, 255, 0.26);
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 86px;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  position: relative;
  transition: background-color 0.35s ease, color 0.35s ease;
}

/* Mouse Glow Spotlight */
.cursor-glow {
  position: fixed;
  top: 0;
  left: 0;
  width: 500px;
  height: 500px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--glow-color) 0%, transparent 70%);
  pointer-events: none;
  transform: translate(-50%, -50%);
  z-index: 0;
  opacity: 0.65;
  transition: opacity 0.3s ease;
}

/* Floating 3D Background Particles */
.bg-particles-container {
  position: fixed;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
  z-index: 0;
}

.bg-float-cube {
  position: absolute;
  width: 22px;
  height: 22px;
  border: 1px solid var(--particle-color);
  border-radius: 4px;
  background: var(--particle-color);
  backdrop-filter: blur(2px);
  transform-style: preserve-3d;
  animation: float-drift 22s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}

button, a { font: inherit; }
a { color: inherit; text-decoration: none; }
button { color: inherit; }
[hidden] { display: none !important; }

/* Topbar */
.topbar {
  position: absolute;
  z-index: 10;
  top: 0;
  left: 0;
  display: flex;
  width: 100%;
  height: 74px;
  align-items: center;
  justify-content: space-between;
  padding: 0 8.1%;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--display);
  font-size: 18px;
  font-weight: 800;
  letter-spacing: -1px;
  transition: transform 0.2s ease;
}
.brand:hover { transform: scale(1.03); }
.brand-light { color: var(--muted-light); font-weight: 500; }
.brand-mark {
  display: grid;
  width: 24px;
  height: 24px;
  grid-template-columns: 1fr 1fr;
  gap: 2px;
  transform: rotate(-8deg);
  transition: transform 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.brand:hover .brand-mark { transform: rotate(82deg) scale(1.1); }
.brand-mark span { border-radius: 2px; background: var(--green); }
.brand-mark span:nth-child(2) { background: #f0bd59; }
.brand-mark span:nth-child(3) { background: #e77355; }
.brand-mark span:nth-child(4) { background: #a6c58e; }

.topbar-actions {
  display: flex;
  align-items: center;
  gap: 14px;
}

.topbar-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 11px;
  border: 1px solid var(--card-border);
  border-radius: 20px;
  background: var(--card-bg);
  color: var(--ink);
  font-size: 11px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
}
.topbar-btn:hover {
  border-color: var(--green);
  transform: translateY(-1px);
}

.theme-picker {
  display: inline-flex;
  align-items: center;
  gap: 3px;
  padding: 3px;
  border: 1px solid var(--card-border);
  border-radius: 24px;
  background: var(--card-bg);
}
.theme-btn {
  display: grid;
  width: 26px;
  height: 26px;
  place-items: center;
  border: 0;
  border-radius: 50%;
  background: transparent;
  font-size: 12px;
  cursor: pointer;
  transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
}
.theme-btn:hover { transform: scale(1.18); }
.theme-btn.is-active {
  background: var(--green-pale);
  box-shadow: 0 0 0 2px var(--green);
  transform: scale(1.08);
}

.topbar-link {
  color: var(--muted);
  font-size: 12px;
  font-weight: 600;
}
.topbar-link span { padding-left: 6px; color: var(--green); }

/* Hero Section */
.hero {
  position: relative;
  display: grid;
  min-height: 680px;
  grid-template-columns: 1fr 0.93fr;
  align-items: center;
  overflow: hidden;
  padding: 85px 12.4% 92px 14.4%;
  background: var(--bg-gradient);
}

.hero::before {
  position: absolute;
  top: 7%;
  right: 2%;
  width: 440px;
  height: 440px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--glow-color) 0%, transparent 72%);
  content: "";
  animation: background-drift 16s ease-in-out infinite alternate;
  pointer-events: none;
}
.hero::after {
  position: absolute;
  inset: 0;
  background-image: radial-gradient(var(--line) 0.8px, transparent 0.8px);
  background-position: 12px 8px;
  background-size: 25px 25px;
  content: "";
  opacity: 0.35;
  pointer-events: none;
  mask-image: linear-gradient(90deg, #000 0%, transparent 47%, #000 100%);
}

.hero-copy { position: relative; z-index: 2; padding-top: 8px; }
.eyebrow {
  display: flex;
  align-items: center;
  gap: 9px;
  color: var(--green);
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 1.1px;
}
.eyebrow-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--green);
  box-shadow: 0 0 0 4px var(--green-pale);
}

h1, h2, h3, p { margin-top: 0; }
.hero h1 {
  margin: 22px 0 19px;
  font-family: var(--display);
  font-size: clamp(43px, 5.5vw, 70px);
  font-weight: 600;
  line-height: 1.07;
  letter-spacing: -4.5px;
}
.hero h1 span { color: var(--green); }
.hero-description {
  max-width: 385px;
  margin-bottom: 26px;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.8;
}

.primary-button {
  display: inline-flex;
  min-height: 47px;
  align-items: center;
  gap: 24px;
  padding: 0 18px;
  border-radius: 6px;
  background: var(--green);
  color: #fff !important;
  font-size: 12px;
  font-weight: 600;
  box-shadow: 0 4px 14px var(--green-glow);
  transition: background 0.2s, transform 0.2s;
}
.primary-button:hover {
  transform: translateY(-2px);
  background: var(--green-dark);
}
.primary-button span { font-size: 16px; }

.hero-note {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 19px;
  color: var(--muted-light);
  font-size: 11px;
}
.note-icon { color: var(--accent-gold); font-size: 15px; }

/* 3D Hero Cube */
.hero-art {
  position: relative;
  z-index: 1;
  display: grid;
  min-height: 480px;
  place-items: center;
}
.art-orbit {
  position: absolute;
  width: 366px;
  height: 366px;
  border: 1px solid var(--line);
  border-radius: 50%;
}
.orbit-two {
  width: 438px;
  height: 438px;
  border-style: dashed;
  border-color: var(--line);
  animation: orbit 90s linear infinite;
}
.orbit-three {
  width: 510px;
  height: 510px;
  border: 1px dotted var(--line);
  opacity: 0.5;
}

.cube-wrap {
  position: relative;
  z-index: 1;
  width: 230px;
  height: 230px;
  perspective: 850px;
  filter: drop-shadow(0 28px 26px var(--shadow-md));
  animation: cube-hover 8s ease-in-out infinite;
  cursor: grab;
  touch-action: none;
  user-select: none;
}
.cube-wrap:active { cursor: grabbing; }

.cube3d {
  position: absolute;
  inset: 0;
  transform: rotateX(-27deg) rotateY(-39deg);
  transform-origin: 50% 50% 0;
  transform-style: preserve-3d;
  transition: transform 0.18s ease-out;
}
.cube3d.is-user-controlled {
  transform: rotateX(var(--view-x, -27deg)) rotateY(var(--view-y, -39deg));
}
.cube-wrap.is-paused { animation-play-state: paused; }
.cube-rotor {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
}
.cube3d:focus-visible {
  outline: 2px solid var(--green);
  outline-offset: 9px;
  border-radius: 15px;
}

.cubelet {
  position: absolute;
  top: 50%;
  left: 50%;
  width: var(--cubelet-size, 70px);
  height: var(--cubelet-size, 70px);
  margin: calc(var(--cubelet-size, 70px) / -2);
  background: #272923;
  transform-style: preserve-3d;
}
.cube-sticker {
  position: absolute;
  inset: 2px;
  border-radius: 5px;
  box-shadow: inset 0 2px 2px rgba(255, 255, 255, 0.32), inset 0 -3px 3px rgba(0, 0, 0, 0.1);
  background: var(--sticker-color);
}
.sticker-front { transform: translateZ(35px); }
.sticker-back { transform: rotateY(180deg) translateZ(35px); }
.sticker-right { transform: rotateY(90deg) translateZ(35px); }
.sticker-left { transform: rotateY(-90deg) translateZ(35px); }
.sticker-top { transform: rotateX(90deg) translateZ(35px); }
.sticker-bottom { transform: rotateX(-90deg) translateZ(35px); }
.cube-turn-layer {
  position: absolute;
  inset: 0;
  transform-style: preserve-3d;
  transform-origin: 50% 50% 0;
}

.float-note {
  position: absolute;
  z-index: 2;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
  border: 1px solid var(--card-border);
  border-radius: 7px;
  background: var(--card-bg);
  color: var(--muted);
  box-shadow: var(--shadow-sm);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.3px;
  backdrop-filter: blur(8px);
}
.note-top { top: 86px; right: 0; }
.note-bottom { bottom: 79px; left: 0; font-family: var(--sans); font-size: 10px; letter-spacing: 0; }
.float-note-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--green);
}
.note-cube { color: var(--green); font-size: 17px; }

.cube-controls {
  position: absolute;
  z-index: 3;
  bottom: 17px;
  left: 50%;
  display: flex;
  align-items: center;
  gap: 7px;
  transform: translateX(-50%);
}
.cube-controls > span {
  margin-right: 4px;
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 7px;
  letter-spacing: 0.25px;
  white-space: nowrap;
}
.cube-controls button {
  display: grid;
  width: 30px;
  height: 30px;
  place-items: center;
  border: 1px solid var(--card-border);
  border-radius: 50%;
  background: var(--card-bg);
  color: var(--green-dark);
  box-shadow: var(--shadow-sm);
  cursor: pointer;
  font-size: 14px;
  transition: transform 0.2s, background 0.2s;
}
.cube-controls button:hover {
  transform: translateY(-2px);
  background: var(--green-pale);
}

.art-sparkle {
  position: absolute;
  color: var(--accent-gold);
  animation: twinkle 3s ease-in-out infinite;
  pointer-events: none;
}
.sparkle-one { top: 119px; left: 54px; font-size: 23px; }
.sparkle-two { right: 26px; bottom: 139px; color: var(--green); font-size: 17px; animation-delay: 1s; }
.sparkle-three { left: 45px; bottom: 85px; color: var(--cube-blue); font-size: 16px; animation-delay: 2s; }

.scroll-cue {
  position: absolute;
  bottom: 25px;
  left: 50%;
  display: flex;
  align-items: center;
  gap: 9px;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.8px;
  transform: translateX(-50%);
}
.scroll-cue span {
  width: 14px;
  height: 20px;
  border: 1px solid var(--muted-light);
  border-radius: 8px;
}
.scroll-cue span::after {
  display: block;
  width: 2px;
  height: 4px;
  margin: 4px auto;
  border-radius: 2px;
  background: var(--green);
  content: "";
  animation: scroll-tick 1.3s ease-in-out infinite;
}

/* Method Section */
.method-section {
  position: relative;
  isolation: isolate;
  overflow: hidden;
  padding: 79px 10.8% 24px;
  background: var(--paper);
  transition: background-color 0.35s ease;
}
.method-section::before {
  position: absolute;
  z-index: 0;
  inset: 0;
  background-image: radial-gradient(var(--line) 0.8px, transparent 0.8px);
  background-position: 10px 7px;
  background-size: 27px 27px;
  content: "";
  opacity: 0.32;
  pointer-events: none;
}
.method-section > * { position: relative; z-index: 1; }

.section-intro {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  max-width: 1050px;
  margin: 0 auto 38px;
}
.section-intro h2 {
  margin: 15px 0 0;
  font-family: var(--display);
  font-size: 42px;
  font-weight: 600;
  line-height: 1.12;
  letter-spacing: -2.1px;
}
.section-intro h2 span { color: var(--green); }
.section-intro > p {
  max-width: 325px;
  margin: 0 8px 5px 25px;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.8;
}

.lesson-layout {
  display: grid;
  max-width: 1050px;
  grid-template-columns: 218px minmax(0, 1fr);
  gap: 24px;
  margin: 0 auto;
  align-items: start;
}

.step-sidebar {
  padding: 17px 14px 14px;
  border: 1px solid var(--card-border);
  border-radius: 9px;
  background: var(--card-bg);
  box-shadow: var(--shadow-sm);
}
.sidebar-caption {
  display: flex;
  justify-content: space-between;
  padding: 0 7px 12px;
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.6px;
}
.sidebar-caption span { color: var(--green); font-weight: 600; }

.step-nav { display: grid; gap: 3px; }
.step-nav-button {
  display: grid;
  min-height: 41px;
  grid-template-columns: 24px 1fr 14px;
  align-items: center;
  gap: 7px;
  padding: 0 8px;
  border: 0;
  border-radius: 5px;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  text-align: left;
  transition: background 0.18s, color 0.18s;
}
.step-nav-button:hover { background: var(--subtle-bg); color: var(--ink); }
.step-nav-button[aria-current="step"] {
  background: var(--green-pale);
  color: var(--green-dark);
}
.nav-number {
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 9px;
}
.step-nav-button[aria-current="step"] .nav-number { color: var(--green); }
.nav-title { font-size: 10px; font-weight: 600; }
.nav-check { color: var(--green); font-size: 11px; font-weight: bold; }

.progress-card {
  margin-top: 20px;
  padding: 12px 9px 5px;
  border-top: 1px solid var(--line);
}
.progress-heading {
  display: flex;
  justify-content: space-between;
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 7px;
  letter-spacing: 0.25px;
}
.progress-heading span + span { color: var(--green); font-weight: 600; }
.progress-track {
  height: 4px;
  margin: 10px 0 7px;
  overflow: hidden;
  border-radius: 8px;
  background: var(--line);
}
.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  border-radius: inherit;
  background: var(--green);
  transition: width 0.4s ease;
}
.progress-card p {
  margin: 0;
  color: var(--muted);
  font-size: 9px;
}
.progress-card p span { color: var(--ink); font-weight: 700; }

.lesson-card {
  display: grid;
  min-height: 480px;
  grid-template-columns: minmax(0, 1.3fr) minmax(230px, 0.8fr);
  overflow: hidden;
  border: 1px solid var(--card-border);
  border-radius: 9px;
  background: var(--card-bg);
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.25s, border-color 0.25s;
}
.lesson-card:hover {
  border-color: var(--card-hover-border);
  box-shadow: var(--shadow-md);
}

.lesson-main {
  position: relative;
  display: flex;
  flex-direction: column;
  padding: 25px 25px 18px;
}
.lesson-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.step-tag, .lesson-time {
  color: var(--green);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.7px;
  font-weight: 600;
}
.lesson-time { color: var(--muted-light); }

.lesson-main h3 {
  margin: 15px 0 8px;
  font-family: var(--display);
  font-size: 25px;
  font-weight: 700;
  line-height: 1.18;
  letter-spacing: -0.8px;
}
.lesson-description {
  min-height: 53px;
  margin-bottom: 15px;
  color: var(--muted);
  font-size: 11px;
  line-height: 1.7;
}

.checklist-block {
  margin-bottom: 13px;
  padding: 11px 12px 9px;
  border: 1px solid var(--card-border);
  border-radius: 6px;
  background: var(--subtle-bg);
}
.checklist-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 5px;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.35px;
}
.checklist-heading > span:last-child { color: var(--green); font-weight: 600; }
.step-checklist { display: grid; gap: 2px; }
.checklist-item {
  display: flex;
  width: 100%;
  align-items: flex-start;
  gap: 8px;
  padding: 5px 3px;
  border: 0;
  border-radius: 4px;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  font-size: 9px;
  line-height: 1.45;
  text-align: left;
  transition: color 0.18s, background 0.18s;
  animation: checklist-arrive 0.35s both;
  animation-delay: calc(var(--item-index, 0) * 45ms);
}
.checklist-item:hover { background: var(--card-bg); }
.checklist-item[aria-pressed="true"] { color: var(--muted); }
.checklist-item[aria-pressed="true"] > span:last-child {
  text-decoration: line-through;
}
.checklist-check {
  display: grid;
  width: 14px;
  height: 14px;
  flex: 0 0 14px;
  place-items: center;
  margin-top: 1px;
  border: 1px solid var(--card-border);
  border-radius: 4px;
  color: #fff;
  font-size: 9px;
  font-weight: bold;
  transition: background 0.18s, border-color 0.18s;
}
.checklist-item[aria-pressed="true"] .checklist-check {
  border-color: var(--green);
  background: var(--green);
}

.completion-message {
  display: flex;
  align-items: center;
  gap: 6px;
  margin: 8px 1px 0;
  color: var(--green);
  font-size: 9px;
  font-weight: 700;
  animation: message-pop 0.3s cubic-bezier(0.2, 0.8, 0.2, 1) both;
}
.completion-message::before { content: "✦"; color: var(--accent-gold); }

.completion-burst {
  position: absolute;
  z-index: 4;
  inset: 0;
  overflow: hidden;
  pointer-events: none;
}
.completion-burst span {
  position: absolute;
  top: 47%;
  left: 50%;
  width: 7px;
  height: 10px;
  border-radius: 2px;
  animation: confetti-pop 0.95s cubic-bezier(0.15, 0.75, 0.35, 1) both;
}

/* Algorithm Block & Twist Hint Card */
.algorithm-block {
  padding: 13px 14px 12px;
  border: 1px solid var(--card-border);
  border-radius: 6px;
  background: var(--subtle-bg);
}
.algorithm-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.45px;
}
.algorithm-heading-right { display: flex; align-items: center; gap: 6px; }
.algorithm-hint {
  color: var(--muted-light);
  font-family: var(--sans);
  font-size: 9px;
}
.algorithm-choices { display: inline-flex; gap: 3px; }
.algorithm-choice {
  padding: 4px 5px;
  border: 1px solid var(--card-border);
  border-radius: 3px;
  background: var(--card-bg);
  color: var(--muted);
  cursor: pointer;
  font-family: var(--sans);
  font-size: 8px;
  font-weight: 600;
  transition: all 0.15s ease;
}
.algorithm-choice[aria-pressed="true"] {
  border-color: var(--green);
  background: var(--green-pale);
  color: var(--green-dark);
}

.algorithm-line {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  min-height: 34px;
  align-items: center;
  margin: 9px 0 6px;
}
.move-token {
  display: inline-flex;
  min-width: 29px;
  height: 27px;
  align-items: center;
  justify-content: center;
  padding: 0 5px;
  border: 1px solid var(--card-border);
  border-radius: 4px;
  background: var(--card-bg);
  color: var(--ink);
  cursor: pointer;
  font-family: var(--mono);
  font-size: 10px;
  font-weight: 700;
  transition: background 0.15s, color 0.15s, transform 0.15s;
}
.move-token:hover {
  border-color: var(--green);
  background: var(--green-pale);
}
.move-token.is-active {
  transform: translateY(-2px);
  border-color: var(--green);
  background: var(--green);
  color: #fff;
  box-shadow: 0 3px 10px var(--green-glow);
}
.algorithm-empty { color: var(--muted-light); font-size: 10px; }

/* Twist & Push Action Hint Card */
.twist-hint-card {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin: 8px 0 10px;
  padding: 8px 10px;
  border-radius: 6px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-left: 3px solid var(--green);
  box-shadow: var(--shadow-sm);
  transition: all 0.25s ease;
}
.twist-hint-card.is-active-twist {
  border-color: var(--green);
  box-shadow: 0 2px 10px var(--green-glow);
}
.twist-hint-badge {
  display: flex;
  align-items: center;
  gap: 6px;
}
.twist-icon { font-size: 12px; }
.twist-action-title {
  color: var(--green);
  font-family: var(--mono);
  font-size: 8.5px;
  font-weight: 700;
  letter-spacing: 0.5px;
}
.twist-hint-instruction {
  color: var(--ink);
  font-size: 9.5px;
  line-height: 1.45;
}

.notation-note {
  color: var(--muted);
  font-size: 8.5px;
  line-height: 1.6;
}
.notation-note strong {
  color: var(--green-dark);
  font-family: var(--mono);
}

.move-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-top: 9px;
}
.play-button {
  display: inline-flex;
  min-height: 29px;
  align-items: center;
  gap: 7px;
  padding: 0 9px;
  border: 0;
  border-radius: 4px;
  background: var(--green-pale);
  color: var(--green-dark);
  cursor: pointer;
  font-size: 9px;
  font-weight: 600;
  transition: background 0.2s, transform 0.2s;
}
.play-button:hover {
  background: var(--green);
  color: #fff;
  transform: translateY(-1px);
}

.move-navigation { display: flex; align-items: center; gap: 7px; }
#move-counter {
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 7px;
  letter-spacing: 0.25px;
}
.move-nav-button {
  display: grid;
  width: 26px;
  height: 26px;
  place-items: center;
  border: 1px solid var(--card-border);
  border-radius: 4px;
  background: var(--card-bg);
  color: var(--ink);
  cursor: pointer;
  font-size: 12px;
  transition: background 0.18s, color 0.18s;
}
.move-nav-button:hover {
  background: var(--green-pale);
  color: var(--green-dark);
}
.play-icon { font-size: 8px; }

.tip-card {
  display: flex;
  gap: 9px;
  margin-top: 13px;
  padding: 10px 11px;
  border-radius: 5px;
  background: var(--subtle-bg);
  border: 1px solid var(--card-border);
}
.tip-icon { color: var(--accent-gold); font-size: 14px; }
.tip-label {
  color: var(--accent-gold);
  font-family: var(--mono);
  font-size: 7px;
  font-weight: 700;
  letter-spacing: 0.5px;
}
.tip-card p {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 9px;
  line-height: 1.55;
}

.lesson-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: auto;
  padding-top: 12px;
}
.text-button, .next-button {
  display: inline-flex;
  min-height: 32px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 0;
  border-radius: 4px;
  cursor: pointer;
  font-size: 9px;
  font-weight: 600;
  transition: background 0.2s;
}
.text-button {
  padding: 0 8px;
  background: transparent;
  color: var(--muted);
}
.text-button:hover:not(:disabled) { background: var(--subtle-bg); color: var(--ink); }
.text-button:disabled { cursor: default; opacity: 0.4; }
.next-button {
  padding: 0 12px;
  background: var(--green);
  color: #fff;
}
.next-button:hover { background: var(--green-dark); }
.next-button.is-complete {
  background: var(--green-pale);
  color: var(--green-dark);
}

/* Visual Panel & Diagram Stage */
.visual-panel {
  display: flex;
  min-height: 100%;
  flex-direction: column;
  padding: 23px 19px 17px;
  border-left: 1px solid var(--line);
  background: var(--panel-bg);
}
.visual-topline {
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.55px;
}
.visual-live {
  display: inline-flex;
  max-width: 68%;
  align-items: center;
  gap: 7px;
  color: var(--green);
  font-size: 7px;
  text-align: right;
  font-weight: 600;
}
.live-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--green);
  box-shadow: 0 0 0 3px var(--green-pale);
}

.diagram-stage {
  position: relative;
  display: grid;
  min-height: 208px;
  flex: 1;
  place-items: center;
  overflow: hidden;
}
.diagram-glow {
  position: absolute;
  width: 168px;
  height: 168px;
  border-radius: 50%;
  background: radial-gradient(circle, var(--glow-color) 0%, transparent 70%);
}

.mini-cube {
  position: relative;
  z-index: 1;
  display: grid;
  width: 150px;
  height: 150px;
  grid-template: repeat(3, 1fr) / repeat(3, 1fr);
  gap: 5px;
  padding: 7px;
  border: 5px solid #282a24;
  border-radius: 9px;
  background: #282a24;
  box-shadow: 0 12px 20px rgba(33, 41, 28, 0.13);
  transform: rotate(-7deg);
  transition: transform 0.4s cubic-bezier(0.2, 0.8, 0.2, 1), box-shadow 0.3s ease;
}
.mini-cube.is-playing {
  transform: rotate(8deg) scale(1.04);
  animation: diagram-play 0.45s ease-in-out infinite alternate;
}
.mini-cube.is-move-selected {
  box-shadow: 0 12px 20px rgba(33, 41, 28, 0.13), 0 0 0 3px var(--green);
}

/* Slice highlight on mini-cube when moves execute */
.mini-cube.highlight-slice-U .mini-tile:nth-child(1),
.mini-cube.highlight-slice-U .mini-tile:nth-child(2),
.mini-cube.highlight-slice-U .mini-tile:nth-child(3) {
  box-shadow: inset 0 0 0 2px var(--green), 0 0 12px var(--green);
  transform: translateY(-2px);
}
.mini-cube.highlight-slice-R .mini-tile:nth-child(3),
.mini-cube.highlight-slice-R .mini-tile:nth-child(6),
.mini-cube.highlight-slice-R .mini-tile:nth-child(9) {
  box-shadow: inset 0 0 0 2px var(--green), 0 0 12px var(--green);
  transform: translateX(2px);
}
.mini-cube.highlight-slice-L .mini-tile:nth-child(1),
.mini-cube.highlight-slice-L .mini-tile:nth-child(4),
.mini-cube.highlight-slice-L .mini-tile:nth-child(7) {
  box-shadow: inset 0 0 0 2px var(--green), 0 0 12px var(--green);
  transform: translateX(-2px);
}
.mini-cube.highlight-slice-D .mini-tile:nth-child(7),
.mini-cube.highlight-slice-D .mini-tile:nth-child(8),
.mini-cube.highlight-slice-D .mini-tile:nth-child(9) {
  box-shadow: inset 0 0 0 2px var(--green), 0 0 12px var(--green);
  transform: translateY(2px);
}
.mini-cube.highlight-slice-F {
  border-color: var(--green);
  box-shadow: 0 0 16px var(--green-glow), 0 0 0 2px var(--green);
}

.mini-tile {
  border-radius: 4px;
  background: #ebece7;
  box-shadow: inset 0 2px 2px rgba(255, 255, 255, 0.4), inset 0 -2px 2px rgba(0, 0, 0, 0.08);
  transition: background 0.35s, transform 0.25s, box-shadow 0.25s;
}
.mini-tile.is-target { transform: scale(0.96); }

/* Directional Twist Overlay on Diagram */
.twist-overlay {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  z-index: 10;
  opacity: 0;
  transition: opacity 0.25s ease;
}
.twist-overlay.is-active {
  opacity: 1;
}
.twist-arrow-svg {
  width: 100%;
  height: 100%;
  overflow: visible;
  filter: drop-shadow(0 2px 6px var(--green-glow));
}
.twist-arrow-path {
  stroke-dasharray: 40;
  animation: twist-dash 1s infinite linear;
}
.twist-cue-tag {
  position: absolute;
  bottom: 8px;
  padding: 3px 8px;
  border-radius: 12px;
  background: var(--ink);
  color: #ffffff;
  font-family: var(--mono);
  font-size: 8px;
  font-weight: 700;
  letter-spacing: 0.4px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.3);
  white-space: nowrap;
}

.diagram-marker {
  position: absolute;
  z-index: 2;
  color: var(--green);
  font-family: var(--mono);
  font-size: 13px;
}
.marker-top { top: 21px; left: 50%; transform: translateX(-50%); }
.marker-right { right: 16px; top: 50%; transform: translateY(-50%); }

.diagram-caption {
  display: flex;
  min-height: 38px;
  align-items: flex-start;
  gap: 8px;
  margin: 3px 2px 14px;
  color: var(--muted);
  font-size: 9px;
  line-height: 1.6;
}
.caption-mark { color: var(--accent-gold); }

.visual-divider { height: 1px; background: var(--line); }
.color-key-title {
  margin: 13px 0 8px;
  color: var(--muted-light);
  font-family: var(--mono);
  font-size: 7px;
  letter-spacing: 0.5px;
}
.color-key {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 8px 4px;
}
.color-key > span {
  display: flex;
  align-items: center;
  gap: 5px;
  color: var(--muted);
  font-size: 8px;
  transition: color 0.18s, transform 0.18s;
}
.color-key > span:hover {
  transform: translateY(-1px);
  color: var(--green-dark);
}
.key-swatch {
  width: 9px;
  height: 9px;
  border-radius: 2px;
  background: var(--cube-white);
  box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.06);
}
.swatch-white  { background: var(--cube-white); }
.swatch-yellow { background: var(--cube-yellow); }
.swatch-green  { background: var(--cube-green); }
.swatch-blue   { background: var(--cube-blue); }
.swatch-orange { background: var(--cube-orange); }
.swatch-red    { background: var(--cube-red); }

.keep-note {
  display: flex;
  gap: 7px;
  margin-top: auto;
  padding-top: 12px;
  color: var(--muted-light);
  font-size: 8px;
  line-height: 1.5;
}
.keep-note > span:first-child { color: var(--green); font-size: 12px; }

/* Footer */
.page-footer {
  display: flex;
  max-width: 1050px;
  min-height: 76px;
  align-items: center;
  justify-content: space-between;
  margin: 38px auto 0;
  border-top: 1px solid var(--line);
}
.footer-brand { font-size: 15px; }
.footer-brand .brand-mark { width: 19px; height: 19px; }
.page-footer > span, .page-footer > a:last-child {
  color: var(--muted-light);
  font-size: 9px;
}
.page-footer > a:last-child {
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.35px;
  font-weight: 600;
  transition: color 0.2s;
}
.page-footer > a:last-child:hover { color: var(--green); }

/* Keyframes */
@keyframes cube-hover {
  0%, 100% { transform: translate3d(0, 0, 0); }
  25% { transform: translate3d(10px, -18px, 0); }
  50% { transform: translate3d(0, -4px, 0); }
  75% { transform: translate3d(-10px, 12px, 0); }
}
@keyframes orbit { to { transform: rotate(360deg); } }
@keyframes twinkle {
  0%, 100% { transform: scale(0.8) rotate(0); opacity: 0.55; }
  50% { transform: scale(1.1) rotate(22deg); opacity: 1; }
}
@keyframes scroll-tick {
  0%, 100% { transform: translateY(0); opacity: 1; }
  65% { transform: translateY(4px); opacity: 0.35; }
}
@keyframes diagram-play {
  from { transform: rotate(-8deg) scale(1); }
  to { transform: rotate(8deg) scale(1.04); }
}
@keyframes background-drift {
  0% { transform: translate3d(0, 0, 0) scale(0.94); }
  100% { transform: translate3d(-32px, 23px, 0) scale(1.08); }
}
@keyframes float-drift {
  0% { transform: translateY(110vh) rotateX(0deg) rotateY(0deg); opacity: 0; }
  10% { opacity: 0.6; }
  90% { opacity: 0.6; }
  100% { transform: translateY(-10vh) rotateX(360deg) rotateY(360deg); opacity: 0; }
}
@keyframes checklist-arrive {
  from { transform: translateY(5px); opacity: 0; }
  to { transform: translateY(0); opacity: 1; }
}
@keyframes message-pop {
  from { transform: translateY(4px) scale(0.97); opacity: 0; }
  to { transform: translateY(0) scale(1); opacity: 1; }
}
@keyframes confetti-pop {
  from { transform: translate(-50%, -50%) scale(0.2); opacity: 1; }
  75% { opacity: 1; }
  to { transform: translate(var(--confetti-x), var(--confetti-y)) rotate(var(--confetti-turn)) scale(1); opacity: 0; }
}
@keyframes twist-dash {
  to { stroke-dashoffset: -40; }
}

/* Responsive */
@media (min-width: 1400px) {
  .hero {
    padding-right: max(12.4%, calc((100vw - 1150px) / 2));
    padding-left: max(14.4%, calc((100vw - 1090px) / 2));
  }
}
@media (max-width: 900px) {
  .topbar { padding-right: 6%; padding-left: 6%; }
  .hero { min-height: 620px; padding-right: 7%; padding-left: 8%; }
  .hero-art { transform: scale(0.87); }
  .method-section { padding-right: 5%; padding-left: 5%; }
  .lesson-layout { grid-template-columns: 190px minmax(0, 1fr); gap: 15px; }
  .lesson-card { grid-template-columns: minmax(0, 1.2fr) minmax(205px, 0.8fr); }
  .lesson-main { padding-right: 18px; padding-left: 18px; }
  .visual-panel { padding-right: 14px; padding-left: 14px; }
}
@media (max-width: 680px) {
  html { scroll-padding-top: 62px; }
  .topbar { height: 62px; gap: 10px; padding-right: 5%; padding-left: 5%; }
  .topbar-actions { min-width: 0; gap: 7px; }
  .topbar-link { display: none; }
  .hero { min-height: 0; grid-template-columns: 1fr; padding: 100px 7% 50px; }
  .hero-copy { max-width: 520px; margin: 0 auto; }
  .hero h1 { margin-top: 18px; font-size: clamp(47px, 11vw, 68px); letter-spacing: -3.7px; }
  .hero-art { min-height: 360px; margin: -2px auto -8px; transform: scale(0.78); transform-origin: center; width: min(100%, 440px); }
  .note-top { top: 37px; right: 1px; }
  .note-bottom { bottom: 36px; left: 0; }
  .scroll-cue { bottom: 16px; white-space: nowrap; }
  .method-section { padding: 57px 5% 12px; }
  .section-intro { display: block; margin-bottom: 26px; }
  .section-intro h2 { font-size: 37px; }
  .section-intro > p { max-width: 400px; margin: 12px 0 0; font-size: 11px; }
  .lesson-layout { min-width: 0; grid-template-columns: minmax(0, 1fr); gap: 12px; }
  .step-sidebar, .lesson-card, .lesson-main, .visual-panel { min-width: 0; }
  .step-sidebar { padding: 12px; }
  .step-nav { display: grid; min-width: 0; grid-template-columns: repeat(7, minmax(0, 1fr)); gap: 4px; overflow: visible; padding-bottom: 0; }
  .step-nav-button { display: grid; width: 100%; min-width: 0; min-height: 40px; grid-template-columns: minmax(0, 1fr); justify-items: center; padding: 0 2px; }
  .nav-title, .nav-check { display: none; }
  .lesson-card { grid-template-columns: minmax(0, 1fr); }
  .visual-panel { border-top: 1px solid var(--line); border-left: 0; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    scroll-behavior: auto !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}