/* ============================================================
   SHARED DESIGN SYSTEM — Engineering Interactive Learning Suite
   Aesthetic: Scientific Precision × Dark Lab
   Font: IBM Plex Mono (monospace authority) + IBM Plex Sans (clarity)
   Color: Deep navy + electric cyan + amber accent
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:wght@400;600;700&family=IBM+Plex+Sans:ital,wght@0,300;0,400;0,600;0,700;1,400&display=swap');

/* ── CSS Variables ── */
:root {
  --bg:          #0a0e1a;
  --bg-2:        #0f1526;
  --panel:       #131929;
  --panel-2:     #1a2238;
  --border:      #1e2d4a;
  --border-2:    #253352;

  --cyan:        #00d4ff;
  --cyan-dim:    #00a8cc;
  --cyan-glow:   rgba(0, 212, 255, 0.15);
  --amber:       #ffb347;
  --amber-dim:   #cc8a2a;
  --green:       #39d98a;
  --red:         #ff5a5f;
  --purple:      #a78bfa;

  --text-primary:   #e8f0fe;
  --text-secondary: #8899bb;
  --text-muted:     #4a5f80;
  --text-code:      #7dd3fc;

  --font-mono: 'IBM Plex Mono', 'Courier New', monospace;
  --font-sans: 'IBM Plex Sans', 'Segoe UI', sans-serif;

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 14px;

  --shadow-panel: 0 4px 24px rgba(0,0,0,0.6), 0 1px 0 rgba(255,255,255,0.03) inset;
  --shadow-glow:  0 0 20px rgba(0, 212, 255, 0.12);

  --transition: 0.18s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ── Reset & Base ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  font-size: 15px;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
  overflow-y: auto;
}

/* Grid background texture */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(0,212,255,0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0,212,255,0.025) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
  z-index: 0;
}

/* Radial glow at top */
body::after {
  content: '';
  position: fixed;
  top: -200px;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 400px;
  background: radial-gradient(ellipse, rgba(0,212,255,0.06) 0%, transparent 70%);
  pointer-events: none;
  z-index: 0;
}

/* ── HOME BUTTON ── */
.home-btn {
  position: fixed;
  top: 16px;
  left: 16px;
  z-index: 9999;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 18px 9px 12px;
  background: var(--panel);
  color: var(--cyan);
  text-decoration: none;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-2);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  transition: all var(--transition);
  box-shadow: var(--shadow-panel), 0 0 0 0 rgba(0,212,255,0);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
}

.home-btn svg {
  width: 16px;
  height: 16px;
  stroke: var(--cyan);
  transition: transform var(--transition);
  flex-shrink: 0;
}

.home-btn:hover {
  background: var(--cyan);
  color: var(--bg);
  border-color: var(--cyan);
  box-shadow: var(--shadow-panel), 0 0 20px rgba(0,212,255,0.4);
  transform: translateY(-1px);
}

.home-btn:hover svg {
  stroke: var(--bg);
  transform: scale(1.1);
}

.home-btn:active {
  transform: translateY(0);
}

/* ── TYPOGRAPHY ── */
h1 {
  font-family: var(--font-mono);
  font-size: clamp(1.3rem, 3vw, 2rem);
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  line-height: 1.2;
}

h1 .accent { color: var(--cyan); }

h2 {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--cyan);
  margin-bottom: 12px;
}

h3 {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}

p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.7;
}

/* ── PANELS ── */
.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-panel);
  position: relative;
  z-index: 1;
  overflow: visible;
}

.panel::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--cyan-dim), transparent);
  opacity: 0.4;
}

.panel-header {
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
  background: var(--panel-2);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

.panel-content {
  padding: 16px 18px;
}

/* ── CONTROLS ── */
.control-group,
.input-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

label {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-secondary);
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

input[type="text"],
input[type="number"],
select,
textarea {
  width: 100%;
  padding: 9px 12px;
  background: var(--bg-2);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  transition: border-color var(--transition), box-shadow var(--transition);
  appearance: none;
  -webkit-appearance: none;
}

input[type="text"]:focus,
input[type="number"]:focus,
select:focus,
textarea:focus {
  outline: none;
  border-color: var(--cyan);
  box-shadow: 0 0 0 3px rgba(0,212,255,0.12);
}

select {
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' fill='none' stroke='%2300d4ff' stroke-width='2'%3E%3Cpath d='M1 1l5 5 5-5'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  padding-right: 36px;
  cursor: pointer;
}

select option {
  background: var(--panel);
  color: var(--text-primary);
}

/* Range inputs */
input[type="range"] {
  width: 100%;
  height: 4px;
  background: var(--border-2);
  border-radius: 999px;
  outline: none;
  appearance: none;
  -webkit-appearance: none;
  cursor: pointer;
  margin-top: 4px;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px;
  height: 16px;
  background: var(--cyan);
  border-radius: 50%;
  border: 2px solid var(--bg);
  box-shadow: 0 0 8px rgba(0,212,255,0.5);
  transition: transform var(--transition), box-shadow var(--transition);
  cursor: grab;
}

input[type="range"]::-webkit-slider-thumb:active {
  cursor: grabbing;
  transform: scale(1.2);
  box-shadow: 0 0 16px rgba(0,212,255,0.8);
}

input[type="range"]::-moz-range-thumb {
  width: 16px;
  height: 16px;
  background: var(--cyan);
  border-radius: 50%;
  border: 2px solid var(--bg);
  cursor: grab;
}

/* Checkboxes */
input[type="checkbox"] {
  width: 16px;
  height: 16px;
  accent-color: var(--cyan);
  cursor: pointer;
}

/* ── BUTTONS ── */
button,
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 9px 20px;
  background: var(--panel-2);
  color: var(--cyan);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  cursor: pointer;
  transition: all var(--transition);
  white-space: nowrap;
}

button:hover,
.btn:hover {
  background: var(--cyan);
  color: var(--bg);
  border-color: var(--cyan);
  box-shadow: 0 0 14px rgba(0,212,255,0.35);
  transform: translateY(-1px);
}

button:active,
.btn:active {
  transform: translateY(0);
  box-shadow: none;
}

.btn-primary {
  background: var(--cyan);
  color: var(--bg);
  border-color: var(--cyan);
  font-weight: 700;
}

.btn-primary:hover {
  background: #00b8d9;
  box-shadow: 0 0 20px rgba(0,212,255,0.5);
}

.btn-amber {
  color: var(--amber);
  border-color: var(--amber-dim);
}
.btn-amber:hover {
  background: var(--amber);
  color: var(--bg);
  border-color: var(--amber);
  box-shadow: 0 0 14px rgba(255,179,71,0.35);
}

/* ── METRICS / DATA BOXES ── */
.metrics-box,
.data-box {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.8;
}

.metric-label {
  color: var(--text-muted);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.metric-value {
  color: var(--cyan);
  font-weight: 700;
  font-size: 1rem;
}

.metric-value.amber { color: var(--amber); }
.metric-value.green { color: var(--green); }
.metric-value.red   { color: var(--red); }

/* Status badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 999px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.badge-stable  { background: rgba(57,217,138,0.12); color: var(--green); border: 1px solid rgba(57,217,138,0.3); }
.badge-unstable{ background: rgba(255,90,95,0.12);  color: var(--red);   border: 1px solid rgba(255,90,95,0.3); }
.badge-warning { background: rgba(255,179,71,0.12); color: var(--amber); border: 1px solid rgba(255,179,71,0.3); }
.badge-info    { background: rgba(0,212,255,0.10);  color: var(--cyan);  border: 1px solid rgba(0,212,255,0.3); }

/* ── INFO / EDUCATIONAL BOXES ── */
.info-box {
  background: var(--bg);
  border-left: 3px solid var(--cyan);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: 12px 16px;
  margin: 10px 0;
}

.info-box.amber { border-left-color: var(--amber); }
.info-box.green { border-left-color: var(--green); }
.info-box.red   { border-left-color: var(--red); }

.info-box p {
  font-size: 0.85rem;
  margin: 0;
}

.info-box strong {
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.8rem;
}

/* Educational callout */
.edu-callout {
  background: linear-gradient(135deg, rgba(0,212,255,0.06), rgba(167,139,250,0.04));
  border: 1px solid rgba(0,212,255,0.2);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  margin: 12px 0;
}

.edu-callout .callout-title {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--cyan);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.edu-callout .callout-title::before {
  content: '⬡';
  font-size: 0.7rem;
}

.edu-callout p {
  font-size: 0.83rem;
  color: var(--text-secondary);
  margin: 0;
}

/* Formula display */
.formula {
  background: var(--bg);
  border: 1px solid var(--border-2);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  color: var(--amber);
  text-align: center;
  letter-spacing: 0.03em;
  overflow-x: auto;
  white-space: nowrap;
}

/* Steps / numbered list */
.steps-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.steps-list li {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  font-size: 0.84rem;
  color: var(--text-secondary);
}

.steps-list li::before {
  content: attr(data-step);
  min-width: 22px;
  height: 22px;
  background: var(--cyan-glow);
  border: 1px solid rgba(0,212,255,0.3);
  border-radius: 50%;
  color: var(--cyan);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-top: 1px;
}

/* Concept list */
.concept-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.concept-list li {
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.84rem;
  color: var(--text-secondary);
  line-height: 1.6;
  transition: border-color var(--transition);
}

.concept-list li:hover {
  border-color: var(--border-2);
}

.concept-list li strong {
  color: var(--cyan);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  display: block;
  margin-bottom: 3px;
}

/* ── CANVAS CONTAINERS ── */
.canvas-container,
.canvas-wrapper {
  position: relative;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: visible;
}

canvas {
  display: block;
  max-width: 100%;
}

/* Overlay title on canvas */
.overlay-title {
  position: absolute;
  top: 10px;
  left: 14px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  z-index: 2;
  pointer-events: none;
}

/* ── PAGE LAYOUT ── */
.page-wrapper {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding: 72px 20px 40px; /* top: clear home btn */
}

.page-header {
  max-width: 1200px;
  width: 100%;
  margin: 0 auto 24px;
  padding: 0 4px;
}

.page-header h1 { margin-bottom: 6px; }

.page-subtitle {
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
}

.topic-tag {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  background: var(--cyan-glow);
  border: 1px solid rgba(0,212,255,0.25);
  border-radius: 999px;
  padding: 3px 10px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--cyan);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 8px;
}

/* Main content grid */
.dashboard,
.grid-container {
  display: grid;
  gap: 18px;
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
}

/* Default: two-column  */
.dashboard { grid-template-columns: 300px 1fr; }
.grid-container { grid-template-columns: 280px 1fr 280px; }

/* ── SEPARATOR / HR ── */
hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 14px 0;
}

/* ── LINKS ── */
a { color: var(--cyan); text-decoration: none; transition: color var(--transition); }
a:hover { color: #fff; }

/* ── SCROLLBAR ── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border-2); border-radius: 999px; }
::-webkit-scrollbar-thumb:hover { background: var(--cyan-dim); }

/* ── RESPONSIVE ── */
@media (max-width: 900px) {
  .dashboard,
  .grid-container {
    grid-template-columns: 1fr;
  }

  .page-wrapper {
    padding: 68px 14px 32px;
  }

  .home-btn {
    top: 10px;
    left: 10px;
    padding: 7px 14px 7px 10px;
    font-size: 0.74rem;
  }

  .canvas-container,
  .canvas-wrapper {
    width: 100% !important;
    height: auto !important;
  }

  canvas {
    width: 100% !important;
    height: auto !important;
  }
}

@media (max-width: 600px) {
  html { font-size: 14px; }

  .panel-header {
    flex-direction: column;
    align-items: flex-start;
  }

  button, .btn {
    width: 100%;
  }

  .formula {
    font-size: 0.78rem;
  }
}

/* ── ANIMATIONS ── */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(16px); }
  to   { opacity: 1; transform: translateY(0); }
}

@keyframes pulse-border {
  0%, 100% { box-shadow: 0 0 0 0 rgba(0,212,255,0.3); }
  50%       { box-shadow: 0 0 0 6px rgba(0,212,255,0); }
}

.panel { animation: fadeInUp 0.4s ease both; }
.panel:nth-child(2) { animation-delay: 0.05s; }
.panel:nth-child(3) { animation-delay: 0.1s; }

/* ── EDUCATIONAL QUICK-FACTS BAR ── */
.edu-bar {
  position: relative;
  z-index: 1;
  width: 100%;
  background: var(--panel-2);
  border-top: 1px solid var(--border);
  margin-top: 40px;
  padding: 0;
}

.edu-bar-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 18px 20px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px 24px;
  align-items: flex-start;
}

.edu-bar-title {
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--cyan);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  white-space: nowrap;
  padding-top: 2px;
  min-width: 110px;
}

.edu-bar-title svg { stroke: var(--cyan); flex-shrink: 0; }

.edu-fact-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  min-width: 180px;
  flex: 1;
  padding: 8px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: border-color var(--transition);
}

.edu-fact-item:hover {
  border-color: var(--border-2);
}

.edu-fact-label {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--amber);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.edu-fact-text {
  font-size: 0.8rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

@media (max-width: 600px) {
  .edu-bar-inner {
    flex-direction: column;
    gap: 8px;
  }

  .edu-fact-item {
    min-width: 0;
    width: 100%;
  }
}

/* ── PRINT ── */
@media print {
  body::before, body::after { display: none; }
  .home-btn { display: none; }
}

/* ── ACCESSIBILITY ── */
:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* ── UTILITY ── */
.text-cyan   { color: var(--cyan); }
.text-amber  { color: var(--amber); }
.text-green  { color: var(--green); }
.text-red    { color: var(--red); }
.text-muted  { color: var(--text-muted); }
.text-mono   { font-family: var(--font-mono); }

.flex        { display: flex; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.flex-between{ display: flex; align-items: center; justify-content: space-between; }
.gap-8       { gap: 8px; }
.gap-12      { gap: 12px; }
.gap-16      { gap: 16px; }
.mt-8        { margin-top: 8px; }
.mt-12       { margin-top: 12px; }
.mt-16       { margin-top: 16px; }
.mb-8        { margin-bottom: 8px; }
.hidden      { display: none !important; }
.full-width  { width: 100%; }

/* ── SHARED.CSS PATCH v2 — Scroll, Responsiveness, Clarity ── */

/* 1. Viewport-locked app shell support:
   Pages that intentionally use height:100vh layouts need this
   so the home button never overlaps content. */
.app-shell,
.viewport-app {
  margin-top: 0;
}

/* 2. Canvas overflow must stay hidden to avoid white strips */
.canvas-container,
.canvas-wrapper {
  overflow: hidden !important;
}

/* 3. Mobile: don't force all buttons to 100% width – only action rows */
@media (max-width: 600px) {
  button, .btn {
    width: auto;
  }
  .btn-row, .action-row, .controls-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
  }
  .btn-row button, .action-row button {
    flex: 1 1 auto;
    min-width: 0;
  }
}

/* 4. Prevent horizontal scroll on any page */
html, body { max-width: 100%; }

/* 5. Better touch targets on mobile */
@media (max-width: 600px) {
  button, .btn, select, input[type="range"] {
    min-height: 40px;
  }
}

/* 6. Smooth scroll for in-page anchors */
html { scroll-padding-top: 80px; }