/* ══════════════════════════════════════════════════
   DESIGN TOKENS — DARK / LIGHT
══════════════════════════════════════════════════ */
:root {
  --bg:       #08090b;
  --bg2:      #0f1014;
  --bg3:      #16171d;
  --bg4:      #1c1d26;
  --border:   rgba(255,255,255,0.06);
  --border2:  rgba(255,255,255,0.12);
  --amber:    #f0b429;
  --blue:     #3b9eff;
  --green:    #34d399;
  --red:      #f87171;
  --cyan:     #67e8f9;
  --purple:   #a78bfa;
  --text:     #e2e4ec;
  --text2:    #9ba3b8;
  --dim:      #5a6278;
  --font-body: 'DM Sans', sans-serif;
  --font-mono: 'Space Mono', monospace;
  --font-disp: 'Playfair Display', serif;
  --nav-h: 64px;
  --radius: 10px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
}
[data-theme="light"] {
  --bg:     #f5f6fa;
  --bg2:    #ffffff;
  --bg3:    #eef0f6;
  --bg4:    #e4e7f0;
  --border: rgba(0,0,0,0.08);
  --border2: rgba(0,0,0,0.15);
  --text:   #1a1c28;
  --text2:  #4a5068;
  --dim:    #8892a8;
  --shadow: 0 4px 24px rgba(0,0,0,0.1);
}

*,*::before,*::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 14px;
  line-height: 1.65;
  min-height: 100vh;
}
[data-theme="dark"] body {
  background-image:
    radial-gradient(ellipse 80% 60% at 50% -10%, rgba(59,158,255,0.08) 0%, transparent 70%),
    linear-gradient(rgba(255,255,255,0.012) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.012) 1px, transparent 1px);
  background-size: 100% 100%, 48px 48px, 48px 48px;
}
code { font-family: var(--font-mono); font-size: 0.85em; color: var(--cyan); background: var(--bg3); padding: 1px 5px; border-radius: 3px; }
a { color: var(--blue); text-decoration: none; }

/* ══════════════════════════════════════════════════
   NAVBAR
══════════════════════════════════════════════════ */
nav {
  position: sticky; top: 0; z-index: 200;
  height: var(--nav-h);
  background: rgba(8,9,11,0.88);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center;
  padding: 0 28px; gap: 0;
}
[data-theme="light"] nav { background: rgba(245,246,250,0.92); }
.nav-brand {
  display: flex; align-items: center; gap: 11px; text-decoration: none;
  flex-shrink: 0; margin-right: 32px;
}
.nav-brand-icon {
  width: 34px; height: 34px; border-radius: 8px;
  background: linear-gradient(135deg, var(--blue), var(--cyan));
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700; font-size: 13px;
  color: #08090b; letter-spacing: -1px; flex-shrink: 0;
}
.nav-brand-text { display: flex; flex-direction: column; line-height: 1.2; }
.nav-brand-title { font-family: var(--font-mono); font-weight: 700; font-size: 14px; color: var(--text); letter-spacing: -0.5px; }
.nav-brand-sub { font-size: 10px; color: var(--dim); letter-spacing: 0.5px; }
.nav-links { display: flex; align-items: stretch; gap: 2px; flex: 1; }
.nav-link {
  padding: 0 14px; height: var(--nav-h); border: none; background: none;
  font-family: var(--font-body); font-size: 13px; font-weight: 500;
  color: var(--text2); cursor: pointer; white-space: nowrap;
  border-bottom: 2px solid transparent; transition: all 0.15s;
  display: flex; align-items: center; gap: 6px;
}
.nav-link:hover { color: var(--text); }
.nav-link.on { color: var(--blue); border-bottom-color: var(--blue); }
.nav-actions { display: flex; gap: 8px; margin-left: auto; flex-shrink: 0; align-items: center; }
.icon-btn {
  padding: 6px 14px; border-radius: 6px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 11px; cursor: pointer; transition: all 0.15s;
}
.icon-btn:hover { color: var(--text); border-color: var(--blue); }
.icon-btn.special { color: var(--purple); border-color: rgba(167,139,250,0.3); background: rgba(167,139,250,0.07); }
.icon-btn.special:hover { background: rgba(167,139,250,0.15); border-color: var(--purple); }
.dl-btn {
  padding: 7px 16px; border-radius: 6px; border: 1px solid rgba(52,211,153,0.4);
  background: rgba(52,211,153,0.1); color: var(--green);
  font-family: var(--font-mono); font-size: 11px; font-weight: 700; cursor: pointer; transition: all 0.15s;
}
.dl-btn:hover { background: rgba(52,211,153,0.2); }

/* ══════════════════════════════════════════════════
   HERO
══════════════════════════════════════════════════ */
#hero {
  padding: 100px 36px 80px;
  max-width: 1100px; margin: 0 auto;
  position: relative;
}
.hero-label {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--font-mono); font-size: 11px; letter-spacing: 1.5px;
  text-transform: uppercase; color: var(--dim);
  border: 1px solid var(--border2); border-radius: 20px;
  padding: 5px 14px; margin-bottom: 28px;
}
.hero-label::before { content: ''; width: 6px; height: 6px; background: var(--green); border-radius: 50%; animation: pulse 2s infinite; }
@keyframes pulse { 0%,100% { opacity:1; } 50% { opacity:0.3; } }
.hero-h {
  font-family: var(--font-disp); font-size: clamp(3rem,7vw,5.5rem);
  font-weight: 800; line-height: 1.05; letter-spacing: -2px;
  margin-bottom: 28px;
}
.hero-h .line1 { display: block; color: var(--text); }
.hero-h .hollow {
  display: block;
  -webkit-text-stroke: 2px var(--blue);
  color: transparent;
}
.hero-sub {
  display: grid; grid-template-columns: 1fr auto; gap: 40px; align-items: start;
  margin-bottom: 52px; max-width: 800px;
}
.hero-p { font-size: 15px; color: var(--text2); line-height: 1.75; max-width: 520px; }
.hero-quick { display: flex; flex-direction: column; gap: 10px; }
.hero-quick-item { font-family: var(--font-mono); font-size: 11px; color: var(--dim); white-space: nowrap; }
.hero-quick-item span { color: var(--amber); margin-right: 6px; }
.hero-grid {
  display: grid; grid-template-columns: repeat(2,1fr);
  border: 1px solid var(--border2); border-radius: var(--radius); overflow: hidden;
}
.hero-stat { padding: 24px 28px; border-right: 1px solid var(--border2); }
.hero-stat:last-child { border-right: none; }
.sv { font-family: var(--font-disp); font-size: 2.4rem; font-weight: 700; color: var(--blue); line-height: 1; margin-bottom: 6px; }
.sl { font-size: 12px; color: var(--dim); font-family: var(--font-mono); }
.hero-cta { display: flex; gap: 12px; margin-top: 36px; }
.btn-primary {
  padding: 12px 24px; border-radius: 8px; background: var(--blue); color: #fff;
  font-family: var(--font-body); font-weight: 600; font-size: 14px;
  border: none; cursor: pointer; transition: all 0.15s;
}
.btn-primary:hover { opacity: 0.88; transform: translateY(-1px); }
.btn-outline {
  padding: 12px 24px; border-radius: 8px; background: transparent;
  border: 1px solid var(--border2); color: var(--text2);
  font-family: var(--font-body); font-weight: 500; font-size: 14px;
  cursor: pointer; transition: all 0.15s;
}
.btn-outline:hover { border-color: var(--blue); color: var(--blue); }

/* ══════════════════════════════════════════════════
   SECTIONS
══════════════════════════════════════════════════ */
section { max-width: 1100px; margin: 0 auto; padding: 88px 36px; }
section + section { border-top: 1px solid var(--border); }
.s-head { display: flex; gap: 20px; align-items: flex-start; margin-bottom: 48px; }
.s-n {
  font-family: var(--font-mono); font-size: 11px; color: var(--dim);
  border: 1px solid var(--border2); border-radius: 4px;
  padding: 4px 8px; flex-shrink: 0; margin-top: 4px;
}
.s-title { font-family: var(--font-disp); font-size: 2rem; font-weight: 700; color: var(--text); line-height: 1.2; margin-bottom: 8px; }
.s-desc { font-size: 14px; color: var(--text2); max-width: 560px; }
.sub-label {
  display: block; font-family: var(--font-mono); font-size: 10px;
  letter-spacing: 2px; text-transform: uppercase; color: var(--dim);
  margin-bottom: 18px;
}
hr.r { border: none; border-top: 1px solid var(--border); margin: 44px 0 28px; }

/* ══════════════════════════════════════════════════
   CARDS
══════════════════════════════════════════════════ */
.card-row {
  display: grid; grid-template-columns: repeat(3,1fr);
  border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden;
  margin-bottom: 40px;
}
.card { padding: 24px; background: var(--bg2); border-right: 1px solid var(--border); }
.card:last-child { border-right: none; }
.c-tag { font-family: var(--font-mono); font-size: 10px; letter-spacing: 1px; text-transform: uppercase; color: var(--dim); margin-bottom: 10px; }
.card h3 { font-size: 15px; font-weight: 600; margin-bottom: 10px; color: var(--text); }
.card p { font-size: 13px; color: var(--text2); line-height: 1.65; }
.tag-badge {
  display: inline-block; margin-top: 14px;
  font-family: var(--font-mono); font-size: 11px; padding: 4px 10px;
  border-radius: 4px; background: var(--bg3); border: 1px solid var(--border2);
  color: var(--cyan);
}

/* ══════════════════════════════════════════════════
   CALLOUT
══════════════════════════════════════════════════ */
.callout {
  border: 1px solid var(--border); border-left: 3px solid var(--blue);
  background: var(--bg2); padding: 16px 20px; margin-bottom: 36px;
  font-size: 13px; color: var(--text2); line-height: 1.7; border-radius: 0 6px 6px 0;
}
.callout strong { color: var(--text); }
.callout.warn { border-left-color: var(--amber); }
.callout.success { border-left-color: var(--green); }

/* ══════════════════════════════════════════════════
   FORMULAS
══════════════════════════════════════════════════ */
.fml-row {
  display: grid; grid-template-columns: repeat(4,1fr);
  border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden;
  margin-bottom: 44px;
}
.fml { padding: 20px; background: var(--bg2); border-right: 1px solid var(--border); }
.fml:last-child { border-right: none; }
.fml-t { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 1px; color: var(--dim); margin-bottom: 12px; }
.fml-e { font-family: var(--font-mono); font-size: 16px; color: var(--cyan); margin-bottom: 8px; font-weight: 700; }
.fml-n { font-size: 12px; color: var(--text2); }
.fml-n strong { color: var(--amber); }

/* ══════════════════════════════════════════════════
   STEPS
══════════════════════════════════════════════════ */
.steps { display: flex; flex-direction: column; gap: 0; margin-bottom: 44px; }
.step { display: flex; gap: 20px; padding: 18px 0; border-bottom: 1px solid var(--border); }
.step:first-child { border-top: 1px solid var(--border); }
.step-icon {
  flex-shrink: 0; width: 36px; height: 36px; border-radius: 50%;
  border: 1px solid var(--border2); background: var(--bg3);
  font-family: var(--font-mono); font-size: 11px; font-weight: 700;
  color: var(--blue); display: flex; align-items: center; justify-content: center;
}
.step-body h4 { font-size: 14px; font-weight: 600; color: var(--text); margin-bottom: 4px; }
.step-body p { font-size: 13px; color: var(--text2); line-height: 1.6; }

/* ══════════════════════════════════════════════════
   TABLE
══════════════════════════════════════════════════ */
.tbl-wrap { overflow-x: auto; margin-bottom: 40px; border: 1px solid var(--border); border-radius: var(--radius); }
table { width: 100%; border-collapse: collapse; font-size: 13px; }
th {
  background: var(--bg3); padding: 11px 16px; text-align: left;
  font-family: var(--font-mono); font-size: 10px; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.5px; color: var(--dim);
  border-bottom: 1px solid var(--border);
}
td { padding: 11px 16px; border-bottom: 1px solid var(--border); color: var(--text2); }
tr:last-child td { border-bottom: none; }
tr:hover td { background: rgba(255,255,255,0.02); }
.td-pure { color: var(--amber); font-family: var(--font-mono); font-size: 12px; }
.td-slot { color: var(--blue); font-family: var(--font-mono); font-size: 12px; }
.td-highlight { color: var(--text); font-family: var(--font-mono); font-weight: 700; }

/* ══════════════════════════════════════════════════
   THROUGHPUT CHART
══════════════════════════════════════════════════ */
.chart-container {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  overflow: hidden; margin-bottom: 40px;
}
.chart-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 20px; border-bottom: 1px solid var(--border);
}
.chart-title { font-family: var(--font-mono); font-size: 11px; text-transform: uppercase; letter-spacing: 1px; color: var(--dim); }
.chart-legend { display: flex; gap: 20px; align-items: center; font-size: 12px; color: var(--text2); }
.legend-item { display: flex; align-items: center; gap: 8px; }
.legend-line-pure { display: inline-block; width: 24px; height: 2px; background: var(--amber); border-top: 2px dashed var(--amber); }
.legend-line-slot { display: inline-block; width: 24px; height: 2px; background: var(--blue); }
#tp-canvas { display: block; width: 100%; padding: 8px; }

/* ══════════════════════════════════════════════════
   SIMULATION
══════════════════════════════════════════════════ */
.sim-outer {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  overflow: hidden; margin-bottom: 32px;
}
.sim-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 20px; border-bottom: 1px solid var(--border);
  background: var(--bg3);
}
.sim-header-title { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 2px; color: var(--dim); }
.speed-badge { display: flex; align-items: center; gap: 6px; font-family: var(--font-mono); font-size: 10px; color: var(--green); }
.speed-dot { width: 6px; height: 6px; background: var(--green); border-radius: 50%; animation: pulse 2s infinite; }
.sim-body { display: grid; grid-template-columns: 260px 1fr; }
.sim-ctrl { padding: 20px; border-right: 1px solid var(--border); display: flex; flex-direction: column; gap: 18px; }
.ctrl-group { display: flex; flex-direction: column; gap: 8px; }
.ctrl-lbl {
  font-family: var(--font-mono); font-size: 10px; text-transform: uppercase;
  letter-spacing: 1px; color: var(--dim);
  display: flex; justify-content: space-between; align-items: center;
}
.ctrl-val { color: var(--cyan); font-weight: 700; }
.rng-wrap input[type="range"] { width: 100%; accent-color: var(--blue); height: 4px; cursor: pointer; }
.proto-row { display: flex; gap: 6px; }
.proto-b {
  flex: 1; padding: 7px; border-radius: 5px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 11px; cursor: pointer; transition: all 0.15s;
}
.proto-b.on { background: rgba(59,158,255,0.15); color: var(--blue); border-color: rgba(59,158,255,0.4); }
.run-btn {
  padding: 10px; border-radius: 6px; border: 1px solid rgba(52,211,153,0.4);
  background: rgba(52,211,153,0.12); color: var(--green);
  font-family: var(--font-mono); font-size: 12px; font-weight: 700;
  cursor: pointer; transition: all 0.15s; margin-top: auto;
}
.run-btn:hover { background: rgba(52,211,153,0.22); }
.run-btn.running { opacity: 0.6; cursor: wait; }
.sim-vis-area { padding: 16px; display: flex; flex-direction: column; gap: 12px; }
.vis-panel { display: flex; flex-direction: column; gap: 6px; }
.vis-label { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 1px; color: var(--dim); }
canvas { display: block; width: 100%; background: var(--bg3); border: 1px solid var(--border); border-radius: 6px; }
.metrics-row { display: grid; grid-template-columns: repeat(4,1fr); gap: 12px; margin-bottom: 20px; }
.m-cell {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; text-align: center;
}
.m-v { font-family: var(--font-disp); font-size: 1.8rem; font-weight: 700; color: var(--text); line-height: 1; margin-bottom: 4px; }
.m-v.green { color: var(--green); }
.m-v.red { color: var(--red); }
.m-v.blue { color: var(--blue); }
.m-l { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 0.5px; color: var(--dim); }
.sim-log {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px; max-height: 180px; overflow-y: auto; font-family: var(--font-mono);
  font-size: 11px; display: flex; flex-direction: column; gap: 3px; margin-bottom: 24px;
}
.log-entry { display: flex; gap: 12px; align-items: baseline; }
.log-t { color: var(--dim); flex-shrink: 0; width: 44px; }
.log-s { color: var(--green); }
.log-c { color: var(--red); }
.log-e { color: var(--dim); }
.log-info { color: var(--dim); }
.anim-wrapper {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; margin-bottom: 8px;
}
.anim-ctrl-row { display: flex; align-items: center; gap: 6px; flex-wrap: wrap; margin-bottom: 10px; }
.anim-btn {
  padding: 5px 12px; border-radius: 5px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 10px; cursor: pointer; transition: all 0.15s;
}
.anim-btn.active { border-color: var(--green); color: var(--green); }
.anim-speed-row { margin-left: auto; display: flex; gap: 4px; align-items: center; }
.anim-spd-lbl { font-family: var(--font-mono); font-size: 10px; color: var(--dim); }
.anim-spd-btn {
  padding: 4px 8px; border-radius: 4px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 10px; cursor: pointer;
}
.anim-spd-btn.on { color: var(--cyan); border-color: var(--cyan); }
.anim-progress-wrap {
  height: 4px; background: var(--bg3); border-radius: 2px;
  margin-bottom: 8px; cursor: pointer; overflow: hidden;
}
.anim-progress-bar { height: 100%; background: var(--blue); width: 0; transition: width 0.1s; }

/* ══════════════════════════════════════════════════
   NUMERICALS
══════════════════════════════════════════════════ */
.num-tabs { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 24px; }
.num-tab {
  padding: 7px 14px; border-radius: 6px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 11px; cursor: pointer; transition: all 0.15s;
}
.num-tab.on { background: rgba(59,158,255,0.15); color: var(--blue); border-color: rgba(59,158,255,0.4); }
.num-prob { display: none; }
.num-prob.on { display: block; }
.prob-card {
  background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 28px; margin-bottom: 24px;
}
.p-num { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 1.5px; color: var(--blue); display: block; margin-bottom: 10px; }
.prob-card h4 { font-size: 15px; font-weight: 600; color: var(--text); margin-bottom: 16px; line-height: 1.5; }
.given {
  font-family: var(--font-mono); font-size: 11px; color: var(--dim);
  background: var(--bg3); border-radius: 6px; padding: 10px 14px;
  margin-bottom: 18px; display: flex; gap: 10px; align-items: baseline;
}
.g-lbl { color: var(--amber); font-weight: 700; text-transform: uppercase; letter-spacing: 1px; font-size: 10px; flex-shrink: 0; }
.sol-steps { display: flex; flex-direction: column; gap: 10px; margin-bottom: 18px; }
.sol { display: flex; gap: 12px; align-items: baseline; font-size: 13px; }
.sol-n {
  flex-shrink: 0; width: 22px; height: 22px; border-radius: 50%;
  background: var(--bg4); border: 1px solid var(--border2);
  font-family: var(--font-mono); font-size: 10px; font-weight: 700; color: var(--dim);
  display: flex; align-items: center; justify-content: center;
}
.sol-c { color: var(--text2); line-height: 1.6; }
.ans {
  background: rgba(52,211,153,0.07); border: 1px solid rgba(52,211,153,0.25);
  border-radius: 6px; padding: 12px 16px; font-size: 13px; color: var(--text);
  line-height: 1.7;
}
.correct { color: var(--green); margin-right: 6px; font-weight: 700; }

/* ══════════════════════════════════════════════════
   SOLVER BASE
══════════════════════════════════════════════════ */
.solver {
  background: var(--bg2); border: 1px solid var(--border2); border-radius: var(--radius);
  overflow: hidden; margin-top: 32px;
}
.solver-header { background: var(--bg3); padding: 12px 20px; border-bottom: 1px solid var(--border); }
.solver-header-lbl { font-family: var(--font-mono); font-size: 10px; letter-spacing: 1.5px; text-transform: uppercase; color: var(--dim); }
.solver-body { padding: 24px; }
#sol-out { display: none; background: var(--bg3); border-radius: 6px; padding: 18px; border: 1px solid var(--border2); }
.sol-out-title { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 1px; color: var(--dim); display: block; margin-bottom: 12px; }

/* ══════════════════════════════════════════════════
   SOLVER PHASE HINT
══════════════════════════════════════════════════ */
.solver-phase-hint {
  font-size: 13px; color: var(--text2); margin-bottom: 18px;
  padding: 10px 14px;
  background: rgba(59,158,255,0.05);
  border-left: 2px solid var(--blue);
  border-radius: 0 6px 6px 0;
}

/* ══════════════════════════════════════════════════
   SOLVER REVEAL BUTTON
══════════════════════════════════════════════════ */
.solver-reveal-btn {
  display: inline-flex; flex-direction: column; align-items: center; gap: 3px;
  padding: 16px 40px;
  background: var(--bg3);
  border: 1px solid var(--border2);
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative; overflow: hidden;
}
.solver-reveal-btn::before {
  content: '';
  position: absolute; inset: 0;
  background: linear-gradient(135deg, rgba(59,158,255,0.08), transparent);
  opacity: 0; transition: opacity 0.2s;
}
.solver-reveal-btn:hover {
  border-color: rgba(59,158,255,0.5);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(0,0,0,0.3);
}
.solver-reveal-btn:hover::before { opacity: 1; }
.srv-icon {
  font-size: 22px; line-height: 1;
  color: var(--blue);
  animation: bounceDown 1.6s ease-in-out infinite;
}
@keyframes bounceDown {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(5px); }
}
.srv-text {
  font-family: var(--font-mono); font-size: 12px; font-weight: 700;
  color: var(--text); letter-spacing: 0.5px;
}
.srv-sub {
  font-size: 10px; color: var(--dim); font-style: italic;
}
.solver-reveal-btn:hover .srv-icon { animation: none; }

/* ══════════════════════════════════════════════════
   SOLVER PHASE 2 — HIDDEN / VISIBLE
══════════════════════════════════════════════════ */
.solver-phase-2-hidden {
  display: none;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.35s ease, transform 0.35s ease;
}
.solver-phase-2-visible {
  display: block;
  opacity: 1;
  transform: translateY(0);
}

/* Phase 2 header row */
.solver-phase2-header {
  display: flex; align-items: center; justify-content: space-between;
  margin-bottom: 18px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}
.solver-phase2-label {
  font-family: var(--font-mono); font-size: 11px; font-weight: 700;
  text-transform: uppercase; letter-spacing: 1.5px;
  color: var(--text2);
}
.solver-back-btn {
  padding: 5px 14px; border-radius: 6px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--dim); font-family: var(--font-mono);
  font-size: 10px; cursor: pointer; transition: all 0.15s;
}
.solver-back-btn:hover { color: var(--blue); border-color: rgba(59,158,255,0.4); }

/* ══════════════════════════════════════════════════
   SMART INPUTS GRID
══════════════════════════════════════════════════ */
.smart-inputs-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
  background: var(--bg3);
  border: 1px solid var(--border2);
  border-radius: 10px;
  padding: 18px;
}
.smart-field { display: flex; flex-direction: column; gap: 5px; }
.smart-label {
  font-size: 11px; font-weight: 600; color: var(--text2);
  text-transform: uppercase; letter-spacing: 0.5px;
}
.smart-var {
  font-family: var(--font-mono); color: var(--cyan); font-size: 12px;
  text-transform: none; letter-spacing: 0; font-weight: 400;
}
.smart-input {
  background: var(--bg4); border: 1px solid var(--border2); border-radius: 6px;
  color: var(--text); font-family: var(--font-mono); font-size: 13px;
  padding: 8px 10px; outline: none; width: 100%;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.smart-input:focus {
  border-color: var(--blue); box-shadow: 0 0 0 2px rgba(59,158,255,0.15);
}
.smart-select {
  background: var(--bg4); border: 1px solid var(--border2); border-radius: 6px;
  color: var(--text2); font-family: var(--font-mono); font-size: 12px;
  padding: 8px 10px; outline: none; cursor: pointer; width: 100%;
}
.smart-hint { font-size: 10px; color: var(--dim); font-style: italic; }

/* ══════════════════════════════════════════════════
   PROBLEM TYPE GRID
══════════════════════════════════════════════════ */
.smart-prob-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 10px;
}
.smart-prob-btn {
  display: flex; flex-direction: column; align-items: flex-start; gap: 4px;
  padding: 14px 16px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: 10px;
  cursor: pointer; text-align: left;
  transition: all 0.18s ease;
  position: relative; overflow: hidden;
}
.smart-prob-btn::before {
  content: ''; position: absolute; inset: 0;
  background: linear-gradient(135deg, rgba(59,158,255,0.06), transparent);
  opacity: 0; transition: opacity 0.18s;
}
.smart-prob-btn:hover {
  border-color: rgba(59,158,255,0.45);
  background: var(--bg4);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,0,0,0.25);
}
.smart-prob-btn:hover::before { opacity: 1; }
.smart-prob-btn.active {
  border-color: var(--blue);
  background: rgba(59,158,255,0.08);
  box-shadow: 0 0 0 2px rgba(59,158,255,0.2), 0 6px 20px rgba(0,0,0,0.3);
}
.spb-icon { font-size: 20px; line-height: 1; margin-bottom: 2px; }
.spb-title { font-size: 13px; font-weight: 700; color: var(--text); line-height: 1.3; }
.spb-desc { font-family: var(--font-mono); font-size: 10px; color: var(--cyan); line-height: 1.5; }
.spb-uses { font-size: 10px; color: var(--dim); margin-top: 2px; font-style: italic; }

/* ══════════════════════════════════════════════════
   SMART SOLVER OUTPUT STEPS
══════════════════════════════════════════════════ */
.ss-output-title {
  font-family: var(--font-mono); font-size: 11px; color: var(--dim);
  letter-spacing: 0.5px; margin-bottom: 20px;
  padding-bottom: 12px; border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 8px; flex-wrap: wrap;
}
.ss-output-badge {
  font-size: 10px; font-weight: 700; padding: 3px 10px; border-radius: 4px;
  background: rgba(59,158,255,0.12); color: var(--blue);
  border: 1px solid rgba(59,158,255,0.25); font-family: var(--font-mono);
}

/* Step accent colours cycling through blue → cyan → purple → amber */
.ss-step { margin-bottom: 10px; border-radius: 10px; overflow: hidden; }
.ss-step:nth-child(4n+1) { --step-accent: var(--blue);   --step-bg: rgba(59,158,255,0.06); }
.ss-step:nth-child(4n+2) { --step-accent: var(--cyan);   --step-bg: rgba(103,232,249,0.06); }
.ss-step:nth-child(4n+3) { --step-accent: var(--purple); --step-bg: rgba(167,139,250,0.06); }
.ss-step:nth-child(4n+0) { --step-accent: var(--amber);  --step-bg: rgba(240,180,41,0.06); }

.ss-step-head {
  display: flex; align-items: center; gap: 12px;
  padding: 11px 14px;
  background: var(--step-bg);
  border-left: 3px solid var(--step-accent);
}
.ss-step-num {
  width: 26px; height: 26px; border-radius: 6px;
  background: var(--step-accent);
  font-family: var(--font-mono); font-size: 11px; font-weight: 700;
  color: var(--bg); display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
}
.ss-step-desc {
  font-size: 13px; font-weight: 600; color: var(--text);
  line-height: 1.4;
}
.ss-step-math {
  font-family: var(--font-mono); font-size: 12.5px; color: var(--text);
  line-height: 2;
  background: var(--bg3);
  padding: 12px 14px 12px 17px;
  border-left: 3px solid var(--step-accent);
  opacity: 0.92;
}

.ss-summary {
  margin-top: 16px; padding: 15px 18px;
  background: rgba(52,211,153,0.08);
  border: 1px solid rgba(52,211,153,0.3);
  border-radius: 10px;
  font-family: var(--font-mono); font-size: 13px;
  line-height: 2; color: var(--text);
}
.ss-note {
  margin-top: 10px; padding: 11px 15px;
  background: rgba(240,180,41,0.06);
  border-left: 3px solid var(--amber);
  border-radius: 6px; font-size: 12px; color: var(--text2);
  line-height: 1.7;
}

/* ══════════════════════════════════════════════════
   COMPARISON
══════════════════════════════════════════════════ */
.compare-grid { display: grid; grid-template-columns: 1fr 1fr; border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; margin-bottom: 40px; }
.compare-col { padding: 28px; background: var(--bg2); }
.compare-col:first-child { border-right: 1px solid var(--border); }
.compare-col-header { font-family: var(--font-mono); font-size: 11px; letter-spacing: 2px; text-transform: uppercase; margin-bottom: 20px; display: flex; align-items: center; gap: 10px; color: var(--text); }
.pure-dot { width: 8px; height: 8px; background: var(--amber); flex-shrink: 0; border-radius: 1px; }
.slot-dot { width: 8px; height: 8px; background: var(--blue); flex-shrink: 0; border-radius: 1px; }
.compare-item { display: flex; gap: 10px; padding: 10px 0; border-bottom: 1px solid var(--border); font-size: 13px; align-items: flex-start; }
.compare-item:last-child { border-bottom: none; }
.compare-icon { color: var(--green); font-family: var(--font-mono); flex-shrink: 0; }
.compare-icon.con { color: var(--red); }
.compare-text { color: var(--text2); line-height: 1.5; }
.prob-table-wrap { overflow-x: auto; margin-bottom: 32px; border: 1px solid var(--border); border-radius: var(--radius); }
.prob-cell-bar { display: flex; align-items: center; gap: 8px; }
.prob-bar { height: 6px; background: var(--blue); border-radius: 3px; min-width: 2px; }
.prob-bar.pure { background: var(--amber); }

/* ══════════════════════════════════════════════════
   VIDEO & REFS
══════════════════════════════════════════════════ */
.vid-wrap { border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.vid-wrap iframe { width: 100%; height: 500px; display: block; border: none; }
.ref-grid { display: grid; grid-template-columns: repeat(3,1fr); gap: 16px; }
.ref-card { background: var(--bg2); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; transition: border-color 0.2s; }
.ref-card:hover { border-color: var(--border2); }
.r-type { font-family: var(--font-mono); font-size: 10px; text-transform: uppercase; letter-spacing: 1px; color: var(--dim); margin-bottom: 8px; }
.ref-card h4 { font-size: 14px; font-weight: 600; margin-bottom: 8px; color: var(--text); }
.ref-card p { font-size: 12px; color: var(--text2); line-height: 1.6; margin-bottom: 12px; }
.ref-link { font-family: var(--font-mono); font-size: 11px; color: var(--blue); }
.ref-link:hover { text-decoration: underline; }

/* ══════════════════════════════════════════════════
   FOOTER
══════════════════════════════════════════════════ */
footer {
  border-top: 1px solid var(--border); padding: 32px 36px;
  display: flex; align-items: center; justify-content: space-between;
  font-family: var(--font-mono); font-size: 11px; color: var(--dim);
  max-width: 100%;
}
footer span { color: var(--text2); }

/* ══════════════════════════════════════════════════
   MODAL BASE
══════════════════════════════════════════════════ */
.modal-bg {
  display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.7);
  backdrop-filter: blur(8px); z-index: 999; align-items: center; justify-content: center;
  padding: 20px;
}
.modal-bg.open { display: flex; }
.modal {
  background: var(--bg2); border: 1px solid var(--border2); border-radius: var(--radius);
  padding: 32px; max-width: 540px; width: 90%; position: relative;
  max-height: 90vh; overflow-y: auto;
}
.modal h3 { font-family: var(--font-disp); font-size: 1.4rem; margin-bottom: 20px; color: var(--text); }
.modal ul { padding-left: 20px; display: flex; flex-direction: column; gap: 10px; font-size: 13px; color: var(--text2); }
.modal li strong { color: var(--text); }
.m-close {
  position: absolute; top: 16px; right: 16px;
  background: var(--bg3); border: 1px solid var(--border2); color: var(--text2);
  border-radius: 6px; padding: 5px 10px; font-family: var(--font-mono); font-size: 11px; cursor: pointer;
  transition: all 0.15s;
}
.m-close:hover { color: var(--red); border-color: var(--red); }

/* ══════════════════════════════════════════════════
   LEARN MODAL
══════════════════════════════════════════════════ */
.learn-modal { max-width: 680px; }
.learn-tabs { display: flex; gap: 4px; margin-bottom: 24px; flex-wrap: wrap; }
.learn-tab {
  padding: 6px 14px; border-radius: 6px; border: 1px solid var(--border2);
  background: var(--bg3); color: var(--text2); font-family: var(--font-mono);
  font-size: 11px; cursor: pointer; transition: all 0.15s;
}
.learn-tab.on { background: rgba(59,158,255,0.15); color: var(--blue); border-color: rgba(59,158,255,0.4); }
.learn-pane { display: none; }
.learn-pane.on { display: block; }
.learn-pane h4 { font-size: 14px; font-weight: 700; color: var(--text); margin-bottom: 10px; margin-top: 18px; }
.learn-pane h4:first-child { margin-top: 0; }
.learn-pane p { font-size: 13px; color: var(--text2); line-height: 1.75; margin-bottom: 12px; }
.learn-pane ul { list-style: disc; padding-left: 18px; margin-bottom: 12px; }
.learn-pane ul li { font-size: 13px; color: var(--text2); line-height: 1.7; margin-bottom: 4px; }
.learn-formula-box {
  background: var(--bg3); border: 1px solid var(--border2); border-radius: 8px;
  padding: 16px 20px; margin: 12px 0; font-family: var(--font-mono); font-size: 13px; color: var(--cyan);
}
.learn-note {
  background: rgba(240,180,41,0.07); border-left: 3px solid var(--amber);
  border-radius: 0 6px 6px 0; padding: 10px 14px; font-size: 12px; color: var(--text2); margin-bottom: 12px;
}
.learn-note strong { color: var(--amber); }

/* ══════════════════════════════════════════════════
   DEVELOPED BY MODAL
══════════════════════════════════════════════════ */
.devby-modal { max-width: 600px; }
.devby-header-tag { font-family: var(--font-mono); font-size: 10px; letter-spacing: 2px; text-transform: uppercase; color: var(--dim); display: block; margin-bottom: 6px; }
.devby-subtitle { font-size: 13px; color: var(--text2); margin-bottom: 28px; line-height: 1.6; }
.devby-subtitle a { color: var(--blue); }
.devby-team { display: flex; flex-direction: column; gap: 16px; }
.devby-card {
  display: flex; gap: 18px; align-items: flex-start;
  background: var(--bg3); border: 1px solid var(--border2); border-radius: var(--radius); padding: 18px;
  transition: border-color 0.2s;
}
.devby-card:hover { border-color: var(--blue); }
.devby-avatar {
  width: 64px; height: 64px; border-radius: 50%; flex-shrink: 0;
  border: 2px solid var(--border2); overflow: hidden; position: relative;
  background: var(--bg4); display: flex; align-items: center; justify-content: center;
}
.devby-avatar img { width: 100%; height: 100%; object-fit: cover; display: block; }
.devby-avatar.prof { border-color: rgba(167,139,250,0.5); }
.devby-info { flex: 1; min-width: 0; }
.devby-role { font-family: var(--font-mono); font-size: 10px; letter-spacing: 1.5px; text-transform: uppercase; color: var(--dim); margin-bottom: 4px; }
.devby-role.prof-role { color: var(--purple); }
.devby-name { font-size: 15px; font-weight: 700; color: var(--text); margin-bottom: 3px; }
.devby-reg { font-family: var(--font-mono); font-size: 11px; color: var(--cyan); margin-bottom: 8px; }
.devby-divider {
  text-align: center; font-family: var(--font-mono); font-size: 10px;
  color: var(--dim); letter-spacing: 2px; text-transform: uppercase;
  padding: 4px 0; position: relative;
}
.devby-divider::before { content: ''; position: absolute; left: 0; right: 0; top: 50%; height: 1px; background: var(--border); }
.devby-divider span { background: var(--bg2); padding: 0 12px; position: relative; z-index: 1; }

/* ══════════════════════════════════════════════════
   ANIMATIONS
══════════════════════════════════════════════════ */
.fade-in { opacity: 0; transform: translateY(16px); transition: opacity 0.55s ease, transform 0.55s ease; }
.fade-in.visible { opacity: 1; transform: translateY(0); }

/* ══════════════════════════════════════════════════
   MASTER CONTROL PANEL
══════════════════════════════════════════════════ */
#masterPanel {
  position: fixed; top: 0; right: -340px; width: 320px; height: 100vh;
  background: #09090f;
  border-left: 1px solid rgba(255,255,255,0.1);
  z-index: 9999;
  display: flex; flex-direction: column;
  transition: right 0.28s cubic-bezier(0.4,0,0.2,1);
  box-shadow: -8px 0 40px rgba(0,0,0,0.6);
  font-family: var(--font-mono); font-size: 12px;
}
#masterPanel.open { right: 0; }
.mp-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: 14px 16px;
  background: rgba(59,158,255,0.06);
  border-bottom: 1px solid rgba(255,255,255,0.08);
  flex-shrink: 0;
}
.mp-title { font-weight: 700; font-size: 13px; color: var(--blue, #3b9eff); letter-spacing: 0.5px; }
.mp-tag {
  font-size: 9px; font-weight: 700; letter-spacing: 1.5px;
  padding: 2px 7px; border-radius: 3px;
  background: rgba(240,180,41,0.12); color: #f0b429;
  border: 1px solid rgba(240,180,41,0.25);
}
.mp-close { background: none; border: none; color: #5a6278; cursor: pointer; font-size: 13px; padding: 2px 6px; border-radius: 4px; transition: color 0.15s; }
.mp-close:hover { color: #e2e4ec; }
.mp-body { flex: 1; overflow-y: auto; padding: 12px; scrollbar-width: thin; scrollbar-color: #333 transparent; }
.mp-section { margin-bottom: 16px; padding: 12px; background: rgba(255,255,255,0.03); border: 1px solid rgba(255,255,255,0.07); border-radius: 8px; }
.mp-section-label { font-size: 10px; font-weight: 700; letter-spacing: 1px; color: #5a6278; text-transform: uppercase; margin-bottom: 10px; }
.mp-theme-grid { display: flex; flex-wrap: wrap; gap: 6px; }
.mp-theme-btn {
  flex: 1; min-width: 50px; padding: 6px 4px; border-radius: 5px; border: 1px solid rgba(255,255,255,0.1);
  background: rgba(255,255,255,0.04); color: #9ba3b8; cursor: pointer;
  font-family: var(--font-mono); font-size: 11px; transition: all 0.15s; text-align: center;
}
.mp-theme-btn:hover { border-color: rgba(59,158,255,0.4); color: #e2e4ec; }
.mp-theme-btn.on { background: rgba(59,158,255,0.15); border-color: rgba(59,158,255,0.5); color: #3b9eff; }
.mp-radio-group { display: flex; flex-direction: column; gap: 7px; }
.mp-radio { display: flex; align-items: center; gap: 8px; color: #9ba3b8; cursor: pointer; font-size: 11px; }
.mp-radio input { accent-color: var(--blue, #3b9eff); }
.mp-toggle-list { display: flex; flex-direction: column; gap: 8px; }
.mp-toggle { display: flex; align-items: center; justify-content: space-between; color: #9ba3b8; cursor: pointer; font-size: 11px; gap: 10px; }
.mp-toggle input[type=checkbox] { display: none; }
.mp-slider {
  width: 32px; height: 17px; border-radius: 9px; flex-shrink: 0;
  background: rgba(255,255,255,0.1); border: 1px solid rgba(255,255,255,0.15);
  position: relative; transition: background 0.2s; cursor: pointer;
}
.mp-slider::after {
  content: ''; position: absolute;
  width: 11px; height: 11px; border-radius: 50%;
  background: #5a6278; top: 2px; left: 2px; transition: all 0.2s;
}
.mp-toggle input:checked + .mp-slider { background: rgba(59,158,255,0.35); border-color: rgba(59,158,255,0.5); }
.mp-toggle input:checked + .mp-slider::after { left: 17px; background: #3b9eff; }
.mp-action-btn {
  padding: 6px 10px; border-radius: 5px; border: 1px solid rgba(255,255,255,0.12);
  background: rgba(255,255,255,0.05); color: #9ba3b8; cursor: pointer;
  font-family: var(--font-mono); font-size: 11px; transition: all 0.15s;
}
.mp-action-btn:hover { background: rgba(59,158,255,0.12); border-color: rgba(59,158,255,0.4); color: #3b9eff; }
.mp-footer { padding: 10px 12px; font-size: 10px; color: #3a3f50; text-align: center; border-top: 1px solid rgba(255,255,255,0.06); flex-shrink: 0; }

/* unit selectors in solver */
#sol-bw-unit, #sol-frame-unit {
  background: var(--bg4); color: var(--text2); border: 1px solid var(--border2);
  border-radius: 5px; padding: 4px; font-family: var(--font-mono); font-size: 12px;
  cursor: pointer; outline: none;
}

/* ══════════════════════════════════════════════════
   RESPONSIVE
══════════════════════════════════════════════════ */
@media (max-width: 900px) {
  .card-row { grid-template-columns: 1fr; }
  .card { border-right: none; border-bottom: 1px solid var(--border); }
  .fml-row { grid-template-columns: 1fr 1fr; }
  .ref-grid { grid-template-columns: 1fr 1fr; }
  .sim-body { grid-template-columns: 1fr; }
  .sim-ctrl { border-right: none; border-bottom: 1px solid var(--border); }
  .hero-sub { grid-template-columns: 1fr; gap: 20px; }
  .hero-grid { grid-template-columns: 1fr; }
  .hero-stat { border-right: none; border-bottom: 1px solid var(--border2); }
  .devby-card { flex-direction: column; align-items: center; text-align: center; }
}
@media (max-width: 640px) {
  .nav-links { display: none; }
  section, #hero { padding: 60px 20px; }
  .metrics-row { grid-template-columns: 1fr 1fr; }
  .compare-grid { grid-template-columns: 1fr; }
  .compare-col:first-child { border-right: none; border-bottom: 1px solid var(--border); }
  .fml-row { grid-template-columns: 1fr; }
  .ref-grid { grid-template-columns: 1fr; }
  .hero-h { font-size: 2.8rem; }
  .nav-actions { gap: 5px; }
  .icon-btn, .dl-btn { padding: 5px 10px; font-size: 10px; }
}