/* =========================================================
   LinkUp · Section 02 — System Concept Layer
   Pure CSS · Deep theme
   ========================================================= */

:root {
  --bg-deep:     #07080d;
  --bg-soft:     #0c0e16;
  --bg-card:     rgba(255, 255, 255, 0.025);
  --line:        rgba(255, 255, 255, 0.08);
  --line-strong: rgba(255, 255, 255, 0.16);

  --fg:          #e9ecf3;
  --fg-mute:     #8b91a3;
  --fg-dim:      #5a6072;

  --accent:      #7c5cff;
  --accent-2:    #4cc9f0;
  --accent-warm: #ff8a5c;

  --glass:       rgba(255, 255, 255, 0.04);
  --glass-strong:rgba(255, 255, 255, 0.07);

  --grad-accent: linear-gradient(120deg, #7c5cff 0%, #4cc9f0 100%);

  --shadow-soft: 0 20px 60px -20px rgba(0,0,0,.6);
  --shadow-acc:  0 0 40px -10px rgba(124,92,255,.45);

  --font-sans:   'Inter', 'SF Pro Display', system-ui, -apple-system, sans-serif;
  --font-mono:   'JetBrains Mono', 'IBM Plex Mono', ui-monospace, monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html, body {
  background: var(--bg-deep);
  color: var(--fg);
  font-family: var(--font-sans);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

body { min-height: 100vh; }

a { color: inherit; text-decoration: none; }

/* ===== Ambient background ===== */
.ambient {
  position: fixed; inset: 0;
  pointer-events: none;
  z-index: 0;
}
.grid-bg {
  position: absolute; inset: 0;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse at 50% 30%, #000 30%, transparent 75%);
  opacity: .35;
}
.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: .55;
  transition: transform .8s cubic-bezier(.2,.7,.2,1);
}
.orb-1 { width: 520px; height: 520px; top: -120px; left: -120px;
  background: radial-gradient(circle, rgba(124,92,255,.55), transparent 70%); }
.orb-2 { width: 460px; height: 460px; top: 40%; right: -160px;
  background: radial-gradient(circle, rgba(76,201,240,.45), transparent 70%); }
.orb-3 { width: 380px; height: 380px; bottom: -120px; left: 30%;
  background: radial-gradient(circle, rgba(255,138,92,.28), transparent 70%); }
.noise {
  position: absolute; inset: 0;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='160' height='160'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='2'/><feColorMatrix values='0 0 0 0 1  0 0 0 0 1  0 0 0 0 1  0 0 0 .06 0'/></filter><rect width='100%' height='100%' filter='url(%23n)'/></svg>");
  opacity: .35;
  mix-blend-mode: overlay;
}
.scanline {
  position: absolute; inset: 0;
  background: repeating-linear-gradient(180deg,
    transparent 0 3px, rgba(255,255,255,.012) 3px 4px);
  pointer-events: none;
}

/* ===== Section shell ===== */
.section {
  position: relative;
  z-index: 1;
  max-width: 1200px;
  margin: 0 auto;
  padding: 64px 40px 120px;
}

/* ===== Continuity bar (signals: this is mid-page) ===== */
.continuity {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 14px 22px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: linear-gradient(180deg, var(--glass), transparent);
  backdrop-filter: blur(14px);
  margin-bottom: 56px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--fg-mute);
}
.cont-link {
  display: flex; align-items: center; gap: 14px;
  padding: 6px 10px;
  border-radius: 10px;
  transition: color .25s, background .25s, transform .25s;
}
.cont-link:hover { color: var(--fg); background: var(--glass-strong); }
.cont-prev:hover { transform: translateX(-2px); }
.cont-next:hover { transform: translateX(2px); }
.cont-arrow { font-size: 16px; color: var(--accent-2); }
.cont-meta { display: flex; flex-direction: column; line-height: 1.2; }
.cont-meta-right { text-align: right; }
.cont-step { font-size: 10px; color: var(--fg-dim); }
.cont-title { font-size: 12px; color: var(--fg); text-transform: none; letter-spacing: .02em; }

.cont-progress { display: flex; align-items: center; gap: 10px; }
.cont-dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--line-strong);
  position: relative;
}
.cont-dot.done { background: var(--fg-dim); }
.cont-dot.live {
  background: var(--accent);
  box-shadow: 0 0 0 4px rgba(124,92,255,.18), 0 0 16px var(--accent);
}
.cont-dot.live::after {
  content: '';
  position: absolute; inset: -6px;
  border-radius: 50%;
  border: 1px solid var(--accent);
  animation: pulseRing 1.8s ease-out infinite;
}
@keyframes pulseRing {
  0% { opacity: .6; transform: scale(.6); }
  100% { opacity: 0; transform: scale(1.6); }
}

/* ===== Section head (small — this is NOT a hero) ===== */
.sec-head { max-width: 760px; margin-bottom: 88px; }
.sec-tag {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: .14em;
  color: var(--fg-mute);
  background: var(--glass);
  margin-bottom: 24px;
}
.tag-dot {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 10px var(--accent);
}
.tag-sep { color: var(--fg-dim); }
.tag-of { color: var(--fg-dim); }

.sec-title {
  font-size: clamp(34px, 4.4vw, 56px);
  line-height: 1.05;
  letter-spacing: -0.02em;
  font-weight: 600;
  margin-bottom: 18px;
}
.grad {
  background: var(--grad-accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.sec-lede {
  font-size: 16px;
  line-height: 1.65;
  color: var(--fg-mute);
  max-width: 620px;
}

/* ===== Reveal ===== */
[data-reveal] {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity .9s cubic-bezier(.2,.7,.2,1), transform .9s cubic-bezier(.2,.7,.2,1);
}
[data-reveal].visible { opacity: 1; transform: none; }

/* ===== Blocks ===== */
.block { margin-bottom: 96px; position: relative; }

.block-head {
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 24px;
  margin-bottom: 36px;
}
.num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--accent-2);
  padding: 6px 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--glass);
  letter-spacing: .12em;
}
.num-lg { font-size: 14px; }
.head-text h3 {
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-bottom: 4px;
}
.head-text p { color: var(--fg-mute); font-size: 14px; }
.head-rule {
  height: 1px; width: 100%; min-width: 60px;
  background: linear-gradient(90deg, var(--line), transparent);
}

/* ===== Comparison ===== */
.compare {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 28px;
  align-items: stretch;
}
.cmp {
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: linear-gradient(180deg, var(--glass-strong), var(--bg-card));
  backdrop-filter: blur(14px);
  transition: transform .35s cubic-bezier(.2,.7,.2,1), border-color .3s, box-shadow .3s;
  will-change: transform;
}
.cmp:hover { border-color: var(--line-strong); box-shadow: var(--shadow-soft); }
.cmp header { margin-bottom: 20px; }
.cmp h4 {
  font-size: 18px; font-weight: 600; margin-top: 10px;
}
.tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: .14em;
  padding: 4px 10px;
  border-radius: 999px;
  text-transform: uppercase;
}
.tag-muted { background: rgba(255,255,255,.05); color: var(--fg-mute); border: 1px solid var(--line); }
.tag-accent {
  background: rgba(124,92,255,.14);
  color: #c9bbff;
  border: 1px solid rgba(124,92,255,.4);
  box-shadow: 0 0 18px rgba(124,92,255,.25);
}
.cmp-list { list-style: none; display: flex; flex-direction: column; gap: 12px; }
.cmp-list li {
  display: flex; flex-direction: column;
  padding: 10px 12px;
  border-left: 2px solid var(--line);
  transition: border-color .25s, transform .25s;
}
.cmp-list li:hover { border-left-color: var(--accent-2); transform: translateX(4px); }
.cmp-list span { font-size: 14px; color: var(--fg); }
.cmp-list i {
  font-style: normal;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--fg-dim);
  margin-top: 2px;
}
.cmp-new .cmp-list li:hover { border-left-color: var(--accent); }
.cmp-new { box-shadow: 0 0 0 1px rgba(124,92,255,.08), 0 30px 80px -30px rgba(124,92,255,.25); }

.vs {
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  gap: 12px; min-width: 60px;
}
.vs-line { width: 1px; flex: 1; background: linear-gradient(180deg, transparent, var(--line-strong), transparent); }
.vs-text {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .2em;
  color: var(--fg-mute);
  padding: 6px 10px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--bg-deep);
}

/* ===== Quote ===== */
.quote-block {
  text-align: center;
  padding: 56px 32px;
  border: 1px solid var(--line);
  border-radius: 20px;
  background:
    radial-gradient(ellipse at 50% 0%, rgba(124,92,255,.10), transparent 60%),
    linear-gradient(180deg, var(--glass), transparent);
  position: relative;
  overflow: hidden;
}
.quote-block .num { position: absolute; top: 20px; left: 20px; }
.quote {
  font-size: clamp(22px, 2.6vw, 32px);
  font-weight: 400;
  letter-spacing: -0.01em;
  line-height: 1.4;
  max-width: 820px;
  margin: 0 auto;
  color: var(--fg);
}
.quote em {
  font-style: normal;
  background: var(--grad-accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  font-weight: 600;
}
.q-mark {
  color: var(--accent);
  font-size: 1.4em;
  line-height: 0;
  vertical-align: -0.2em;
  margin-right: 4px;
  opacity: .7;
}
.q-end { margin-left: 4px; margin-right: 0; }
.quote-foot {
  margin-top: 20px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .14em;
  color: var(--fg-dim);
  text-transform: uppercase;
}

/* ===== Diagram ===== */
.diagram { padding: 0; }
.diagram-frame {
  position: relative;
  padding: 56px 48px 88px;
  border: 1px solid var(--line);
  border-radius: 22px;
  background:
    radial-gradient(ellipse at 50% 120%, rgba(76,201,240,.10), transparent 60%),
    linear-gradient(180deg, var(--glass), transparent);
  overflow: hidden;
}
.frame-corner {
  position: absolute; width: 16px; height: 16px;
  border: 1px solid var(--accent-2);
  opacity: .7;
}
.frame-corner.tl { top: 12px; left: 12px; border-right: none; border-bottom: none; }
.frame-corner.tr { top: 12px; right: 12px; border-left: none; border-bottom: none; }
.frame-corner.bl { bottom: 12px; left: 12px; border-right: none; border-top: none; }
.frame-corner.br { bottom: 12px; right: 12px; border-left: none; border-top: none; }
.frame-label {
  position: absolute; top: 14px; left: 50%; transform: translateX(-50%);
  font-family: var(--font-mono); font-size: 10px; letter-spacing: .25em;
  color: var(--fg-dim);
}

.modules {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
  margin-bottom: 36px;
}
.module {
  position: relative;
  padding: 24px 20px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background:
    radial-gradient(220px circle at var(--mx,50%) var(--my,50%), rgba(124,92,255,.18), transparent 60%),
    var(--glass);
  display: flex; flex-direction: column; gap: 8px;
  cursor: pointer;
  transition: transform .35s, border-color .3s, box-shadow .3s;
  animation: floatY 6s ease-in-out infinite;
  animation-delay: calc(var(--i) * 0.4s);
}
@keyframes floatY {
  0%,100% { transform: translateY(0); }
  50%    { transform: translateY(-4px); }
}
.module:hover, .module.active {
  border-color: rgba(124,92,255,.5);
  box-shadow: var(--shadow-acc);
  transform: translateY(-4px);
}
.m-id {
  font-family: var(--font-mono); font-size: 11px;
  letter-spacing: .14em; color: var(--accent-2);
}
.m-name { font-size: 16px; font-weight: 600; }
.m-status {
  font-family: var(--font-mono); font-size: 10px;
  color: var(--fg-dim); letter-spacing: .12em; text-transform: uppercase;
}
.m-status::before {
  content: '●'; color: #5cffa8; margin-right: 6px; font-size: 8px;
  vertical-align: middle;
}

.state-layer {
  position: relative;
  padding: 22px 24px;
  border: 1px dashed rgba(124,92,255,.35);
  border-radius: 14px;
  background: linear-gradient(90deg, rgba(124,92,255,.08), rgba(76,201,240,.06));
  display: flex; align-items: center; gap: 18px;
  overflow: hidden;
}
.state-pulse {
  width: 10px; height: 10px; border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 14px var(--accent);
  animation: blink 1.8s ease-in-out infinite;
}
@keyframes blink {
  0%,100% { opacity: 1; }
  50% { opacity: .3; }
}
.state-text {
  font-family: var(--font-mono); font-size: 11px;
  letter-spacing: .2em; color: var(--fg-mute);
}
.state-meta {
  margin-left: auto;
  font-family: var(--font-mono); font-size: 11px;
  letter-spacing: .08em; color: var(--fg-dim);
  transition: color .25s;
}

/* ===== Principles ===== */
.principles {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.principle {
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: linear-gradient(180deg, var(--glass), transparent);
  transition: transform .35s cubic-bezier(.2,.7,.2,1), border-color .3s, box-shadow .3s;
  position: relative; overflow: hidden;
}
.principle::before {
  content: ''; position: absolute; inset: 0;
  background: radial-gradient(400px circle at var(--mx,50%) var(--my,50%), rgba(124,92,255,.10), transparent 60%);
  opacity: 0; transition: opacity .3s;
  pointer-events: none;
}
.principle:hover { border-color: var(--line-strong); box-shadow: var(--shadow-soft); }
.principle:hover::before { opacity: 1; }
.p-num {
  font-family: var(--font-mono); font-size: 11px;
  color: var(--accent-2); letter-spacing: .14em;
}
.principle h5 {
  font-size: 16px; font-weight: 600; margin: 10px 0 8px;
}
.principle p { font-size: 13.5px; color: var(--fg-mute); line-height: 1.55; }

/* ===== Interaction Shift ===== */
.shift-stage {
  position: relative;
  height: 320px;
  border: 1px solid var(--line);
  border-radius: 20px;
  overflow: hidden;
  background: linear-gradient(180deg, var(--glass), transparent);
  --shift: 50%;
}
.shift-side {
  position: absolute; inset: 0;
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  gap: 28px;
}
.shift-left  { clip-path: inset(0 calc(100% - var(--shift)) 0 0); background: rgba(255,138,92,.04); }
.shift-right { clip-path: inset(0 0 0 var(--shift)); background: rgba(124,92,255,.06); }

.frag { display: grid; grid-template-columns: repeat(3, 60px); gap: 16px; }
.frag-box {
  width: 60px; height: 60px;
  background: rgba(255,138,92,.18);
  border: 1px solid rgba(255,138,92,.4);
  border-radius: 8px;
  animation: jitter 2.4s ease-in-out infinite;
}
.frag-box:nth-child(2) { animation-delay: .2s; }
.frag-box:nth-child(3) { animation-delay: .4s; }
.frag-box:nth-child(4) { animation-delay: .1s; }
.frag-box:nth-child(5) { animation-delay: .3s; }
.frag-box:nth-child(6) { animation-delay: .5s; }
@keyframes jitter {
  0%,100% { transform: translate(0,0); }
  50% { transform: translate(2px,-2px); }
}

.unified {
  position: relative; width: 180px; height: 180px;
  display: flex; align-items: center; justify-content: center;
}
.unified-core {
  width: 80px; height: 80px; border-radius: 50%;
  background: var(--grad-accent);
  box-shadow: 0 0 60px rgba(124,92,255,.6);
  animation: pulseCore 3s ease-in-out infinite;
}
@keyframes pulseCore {
  0%,100% { transform: scale(1); }
  50% { transform: scale(1.06); }
}
.unified-ring, .unified-ring.r2 {
  position: absolute; border-radius: 50%;
  border: 1px solid rgba(124,92,255,.4);
  animation: ringExpand 3s linear infinite;
}
.unified-ring { width: 130px; height: 130px; }
.unified-ring.r2 { width: 170px; height: 170px; animation-delay: 1.5s; opacity: .5; }
@keyframes ringExpand {
  0% { transform: scale(.9); opacity: .8; }
  100% { transform: scale(1.15); opacity: 0; }
}

.shift-label {
  font-family: var(--font-mono); font-size: 10px;
  letter-spacing: .2em; color: var(--fg-mute);
  text-transform: uppercase;
}

.shift-divider {
  position: absolute; top: 0; bottom: 0;
  left: 50%;
  width: 2px;
  background: linear-gradient(180deg, transparent, var(--accent), var(--accent-2), transparent);
  cursor: ew-resize;
  z-index: 5;
  transform: translateX(-50%);
}
.handle {
  position: absolute; top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--bg-deep);
  border: 1px solid var(--line-strong);
  display: flex; align-items: center; justify-content: center;
  gap: 4px;
  box-shadow: 0 0 24px rgba(124,92,255,.4);
}
.handle span {
  width: 2px; height: 12px; background: var(--fg-mute); border-radius: 2px;
}

.shift-controls {
  display: flex; align-items: center; gap: 16px;
  margin-top: 22px;
}
.ctrl-end {
  font-family: var(--font-mono); font-size: 10px;
  letter-spacing: .12em; color: var(--fg-dim);
}
.shift-slider {
  flex: 1;
  -webkit-appearance: none; appearance: none;
  height: 4px;
  background: linear-gradient(90deg, var(--accent-warm), var(--accent));
  border-radius: 2px;
  outline: none;
}
.shift-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 18px; height: 18px;
  border-radius: 50%;
  background: var(--fg);
  border: 2px solid var(--accent);
  box-shadow: 0 0 16px var(--accent);
  cursor: pointer;
}
.shift-slider::-moz-range-thumb {
  width: 18px; height: 18px; border-radius: 50%;
  background: var(--fg); border: 2px solid var(--accent);
  box-shadow: 0 0 16px var(--accent); cursor: pointer;
}

/* ===== Final statement ===== */
.final {
  text-align: center;
  padding: 72px 32px;
  border: 1px solid var(--line);
  border-radius: 22px;
  background:
    radial-gradient(ellipse at 50% 0%, rgba(76,201,240,.10), transparent 60%),
    linear-gradient(180deg, var(--glass), transparent);
  position: relative; overflow: hidden;
}
.final .num { position: absolute; top: 20px; left: 20px; }
.final-title {
  font-size: clamp(28px, 3.6vw, 44px);
  line-height: 1.25;
  letter-spacing: -0.015em;
  font-weight: 500;
  max-width: 820px;
  margin: 0 auto 18px;
}
.rotator {
  display: inline-block;
  position: relative;
  vertical-align: bottom;
  min-width: 240px;
  height: 1.1em;
  overflow: hidden;
  text-align: left;
}
.rotator > span {
  position: absolute; left: 0; right: 0;
  opacity: 0;
  transform: translateY(100%);
  background: var(--grad-accent);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  font-weight: 700;
}
.rotator > span.in {
  animation: rotIn .55s cubic-bezier(.2,.7,.2,1) forwards;
}
.rotator > span.out {
  animation: rotOut .55s cubic-bezier(.2,.7,.2,1) forwards;
}
@keyframes rotIn {
  0%   { opacity: 0; transform: translateY(100%); }
  100% { opacity: 1; transform: translateY(0); }
}
@keyframes rotOut {
  0%   { opacity: 1; transform: translateY(0); }
  100% { opacity: 0; transform: translateY(-100%); }
}
.final-sub {
  font-size: 14px;
  font-family: var(--font-mono);
  letter-spacing: .14em;
  color: var(--fg-mute);
  text-transform: uppercase;
}

/* ===== Section end marker (page continues) ===== */
.sec-end {
  display: flex; align-items: center; justify-content: center;
  gap: 16px;
  margin-top: 80px;
  flex-wrap: wrap;
}
.end-rule {
  flex: 1; max-width: 200px;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--line-strong), transparent);
}
.end-label {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: .25em;
  color: var(--fg-dim);
  text-transform: uppercase;
}
.end-next {
  width: 100%;
  text-align: center;
  margin-top: 16px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .14em;
  color: var(--fg-mute);
  text-transform: uppercase;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  transition: color .25s, border-color .25s, background .25s;
}
.end-next:hover {
  color: var(--fg);
  border-color: var(--accent);
  background: rgba(124,92,255,.06);
}
.end-arrow {
  display: inline-block;
  margin-left: 8px;
  animation: bobDown 2s ease-in-out infinite;
}
@keyframes bobDown {
  0%,100% { transform: translateY(0); }
  50%     { transform: translateY(4px); }
}

/* ===== Responsive ===== */
@media (max-width: 960px) {
  .compare { grid-template-columns: 1fr; }
  .vs { flex-direction: row; min-width: 0; }
  .vs-line { height: 1px; width: 100%; flex: 1; background: linear-gradient(90deg, transparent, var(--line-strong), transparent); }
  .modules { grid-template-columns: repeat(2, 1fr); }
  .principles { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 640px) {
  .section { padding: 40px 20px 80px; }
  .continuity { flex-wrap: wrap; gap: 14px; }
  .cont-progress { order: -1; width: 100%; justify-content: center; }
  .principles { grid-template-columns: 1fr; }
  .modules { grid-template-columns: 1fr 1fr; }
  .state-layer { flex-wrap: wrap; }
  .state-meta { margin-left: 0; width: 100%; }
  .shift-stage { height: 260px; }
}