/* ===========================
   EQUATION FLOW — STYLE SYSTEM
   Theme: Sharp Pastel Brown/Green/Blue
   =========================== */

:root {
  --bg: #0f0e0c;
  --bg2: #161512;
  --bg3: #1e1c18;
  --bg4: #252219;
  --surface: #2a261e;
  --surface2: #322e24;
  --border: #3d3829;
  --border2: #4a4535;

  --text: #e8e0cc;
  --text2: #b8ad97;
  --text3: #7a7260;
  --text-muted: #504a3c;

  /* Pastel accents */
  --green: #a8c5a0;
  --green-bright: #c2deba;
  --green-dim: #6a9464;
  --blue: #9ab8c8;
  --blue-bright: #b8d4e8;
  --blue-dim: #5a8499;
  --brown: #c4a882;
  --brown-bright: #dfc4a0;
  --brown-dim: #8a7258;
  --rose: #c8a09a;
  --amber: #c8b47a;

  /* Graph */
  --graph-line: #a8c5a0;
  --graph-glow: rgba(168, 197, 160, 0.4);
  --graph-fill: rgba(168, 197, 160, 0.06);
  --axis-color: rgba(184, 173, 151, 0.25);
  --grid-color: rgba(184, 173, 151, 0.07);

  --radius: 8px;
  --radius-lg: 14px;
  --radius-xl: 20px;

  --font-display: 'DM Serif Display', serif;
  --font-ui: 'Syne', sans-serif;
  --font-mono: 'Space Mono', monospace;

  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 48px rgba(0,0,0,0.6);
  --glow-green: 0 0 20px rgba(168,197,160,0.25);
  --glow-blue: 0 0 20px rgba(154,184,200,0.25);
}

body.light {
  --bg: #f5f0e8;
  --bg2: #ede7d8;
  --bg3: #e4dcc8;
  --bg4: #dbd2ba;
  --surface: #d4c9b0;
  --surface2: #cbbfa4;
  --border: #b8ad97;
  --border2: #a49880;

  --text: #2a2518;
  --text2: #4a4232;
  --text3: #6a6050;
  --text-muted: #9a9080;

  --green: #5a8454;
  --green-bright: #4a7444;
  --green-dim: #8aaa84;
  --blue: #4a7494;
  --blue-bright: #3a6484;
  --blue-dim: #7aa4b4;
  --brown: #8a6444;
  --brown-bright: #7a5434;
  --brown-dim: #aa8464;

  --graph-line: #4a7454;
  --graph-glow: rgba(74,116,84,0.25);
  --graph-fill: rgba(74,116,84,0.08);
  --axis-color: rgba(42,37,24,0.3);
  --grid-color: rgba(42,37,24,0.08);
}

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

html { font-size: 14px; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-ui);
  min-height: 100vh;
  overflow-x: hidden;
  transition: background 0.3s, color 0.3s;
}

/* Noise texture overlay */
.noise-overlay {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 1000;
  opacity: 0.03;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
}

/* HEADER */
.app-header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  background: var(--bg2);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(8px);
}

.logo-area {
  display: flex;
  align-items: center;
  gap: 12px;
}

.logo-icon {
  font-size: 2.2rem;
  color: var(--green);
  line-height: 1;
  filter: drop-shadow(0 0 10px var(--green));
  animation: pulse-glow 2.5s ease-in-out infinite;
}

@keyframes pulse-glow {
  0%, 100% { filter: drop-shadow(0 0 10px var(--green)); }
  50% { filter: drop-shadow(0 0 20px var(--green-bright)); }
}

.logo-text h1 {
  font-family: var(--font-display);
  font-size: 1.5rem;
  color: var(--brown-bright);
  letter-spacing: 0.02em;
  line-height: 1;
}

.tagline {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--text3);
  letter-spacing: 0.08em;
}

.controls-right {
  display: flex;
  gap: 8px;
}

.btn-icon {
  width: 38px;
  height: 38px;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text2);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
}
.btn-icon:hover { background: var(--surface2); color: var(--green); border-color: var(--green-dim); }
.btn-icon svg { width: 16px; height: 16px; }

/* MAIN LAYOUT */
.app-main {
  display: grid;
  grid-template-columns: 220px 1fr 260px;
  height: calc(100vh - 65px);
  gap: 0;
}

/* PANELS */
.presets-panel, .search-panel {
  background: var(--bg2);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  padding: 20px 14px;
}

.search-panel {
  border-right: none;
  border-left: 1px solid var(--border);
}

.presets-panel::-webkit-scrollbar,
.search-panel::-webkit-scrollbar {
  width: 4px;
}
.presets-panel::-webkit-scrollbar-track,
.search-panel::-webkit-scrollbar-track { background: transparent; }
.presets-panel::-webkit-scrollbar-thumb,
.search-panel::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 2px; }

.panel-title {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--text3);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

/* PRESET GROUPS */
.preset-group {
  margin-bottom: 20px;
}

.preset-group-title {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--blue-dim);
  margin-bottom: 8px;
  padding-left: 2px;
}

.preset-btn {
  display: block;
  width: 100%;
  text-align: left;
  padding: 9px 12px;
  margin-bottom: 4px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text2);
  cursor: pointer;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  transition: all 0.18s;
  line-height: 1.3;
}

.preset-btn:hover {
  background: var(--surface);
  border-color: var(--green-dim);
  color: var(--green-bright);
  transform: translateX(2px);
}

.preset-btn.active {
  background: var(--surface2);
  border-color: var(--green);
  color: var(--green-bright);
  box-shadow: var(--glow-green);
}

.preset-btn .preset-name {
  display: block;
  font-weight: 700;
  margin-bottom: 2px;
  color: inherit;
}

.preset-btn .preset-eq {
  display: block;
  font-size: 0.64rem;
  color: var(--text3);
  font-style: italic;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.preset-btn.active .preset-eq { color: var(--green-dim); }

/* VISUALIZER CENTER */
.visualizer-section {
  display: flex;
  flex-direction: column;
  background: var(--bg);
  overflow: hidden;
}

.equation-display {
  padding: 16px 24px 12px;
  display: flex;
  align-items: baseline;
  gap: 10px;
  border-bottom: 1px solid var(--border);
  background: var(--bg2);
  min-height: 52px;
}

.eq-label {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text3);
}

.eq-text {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1.5rem;
  color: var(--brown-bright);
  letter-spacing: 0.02em;
  transition: color 0.3s;
}

/* CANVAS */
.canvas-wrapper {
  flex: 1;
  position: relative;
  overflow: hidden;
}

#mainCanvas {
  width: 100%;
  height: 100%;
  display: block;
}

.canvas-overlay-info {
  position: absolute;
  top: 12px;
  right: 14px;
  display: flex;
  gap: 6px;
}

.info-chip {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  padding: 4px 8px;
  background: rgba(15,14,12,0.7);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text3);
  backdrop-filter: blur(4px);
}

/* PLAYBACK BAR */
.playback-bar {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 12px 20px;
  background: var(--bg2);
  border-top: 1px solid var(--border);
  flex-wrap: wrap;
}

.play-btn {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--green-dim);
  border: none;
  color: var(--bg);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  flex-shrink: 0;
}
.play-btn:hover { background: var(--green); transform: scale(1.05); box-shadow: var(--glow-green); }
.play-btn svg { width: 18px; height: 18px; }

.slider-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 100px;
}

.slider-group label {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--text3);
  letter-spacing: 0.05em;
  display: flex;
  justify-content: space-between;
}

.slider-group label span {
  color: var(--blue);
  font-weight: 700;
}

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 3px;
  background: var(--border2);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--green);
  border: 2px solid var(--bg);
  cursor: pointer;
  box-shadow: 0 0 6px var(--green-dim);
}

input[type="range"]:focus::-webkit-slider-thumb {
  box-shadow: 0 0 12px var(--green);
}

.btn-secondary {
  padding: 8px 14px;
  background: transparent;
  border: 1px solid var(--border2);
  border-radius: var(--radius);
  color: var(--text3);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  cursor: pointer;
  transition: all 0.2s;
  white-space: nowrap;
}
.btn-secondary:hover { border-color: var(--rose); color: var(--rose); }

/* SEARCH PANEL INTERNALS */
.search-box {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 14px;
  margin-bottom: 20px;
}

.search-label {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text3);
  margin-bottom: 10px;
}

.input-row {
  display: flex;
  gap: 8px;
  margin-bottom: 10px;
}

.eq-input {
  flex: 1;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border2);
  border-radius: var(--radius);
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  outline: none;
  transition: all 0.2s;
}

.eq-input:focus {
  border-color: var(--green-dim);
  box-shadow: 0 0 0 3px rgba(168,197,160,0.1);
}

.eq-input::placeholder { color: var(--text-muted); }

.btn-plot {
  padding: 10px 16px;
  background: var(--green-dim);
  border: none;
  border-radius: var(--radius);
  color: var(--bg);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s;
  white-space: nowrap;
}
.btn-plot:hover { background: var(--green); box-shadow: var(--glow-green); }

.hint-text {
  font-family: var(--font-mono);
  font-size: 0.64rem;
  color: var(--text-muted);
  line-height: 1.6;
}

.hint-text code {
  background: var(--surface);
  padding: 1px 5px;
  border-radius: 3px;
  color: var(--blue);
  font-size: 0.62rem;
}

.error-msg {
  margin-top: 8px;
  padding: 8px 10px;
  background: rgba(200,100,90,0.1);
  border: 1px solid rgba(200,100,90,0.3);
  border-radius: var(--radius);
  color: var(--rose);
  font-family: var(--font-mono);
  font-size: 0.68rem;
}

/* SUGGESTIONS */
.suggestions-title {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--brown-dim);
  margin-bottom: 10px;
}

.quick-list {
  display: flex;
  flex-direction: column;
  gap: 4px;
  margin-bottom: 20px;
}

.quick-btn {
  padding: 7px 10px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text3);
  font-family: var(--font-mono);
  font-size: 0.68rem;
  cursor: pointer;
  text-align: left;
  transition: all 0.18s;
}
.quick-btn:hover {
  background: var(--surface);
  border-color: var(--amber);
  color: var(--amber);
}

/* SOUND PANEL */
.sound-panel {
  margin-bottom: 20px;
}

.sound-options {
  display: flex;
  gap: 6px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.sound-opt {
  padding: 6px 12px;
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text3);
  font-family: var(--font-mono);
  font-size: 0.68rem;
  cursor: pointer;
  transition: all 0.18s;
}

.sound-opt:hover { border-color: var(--blue-dim); color: var(--blue); }
.sound-opt.active {
  background: var(--surface);
  border-color: var(--blue);
  color: var(--blue-bright);
  box-shadow: var(--glow-blue);
}

.mt8 { margin-top: 8px; }

/* PROPERTIES */
.props-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px;
}

.prop-item {
  background: var(--bg3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 8px;
}

.prop-label {
  font-family: var(--font-mono);
  font-size: 0.6rem;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 3px;
}

.prop-value {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--amber);
  font-weight: 700;
}

/* ========== SCROLLBAR ========== */
::-webkit-scrollbar { width: 5px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border2); border-radius: 3px; }

/* ========== ANIMATIONS ========== */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.fade-in { animation: fadeIn 0.35s ease forwards; }

/* ========== RESPONSIVE ========== */
@media (max-width: 900px) {
  .app-main {
    grid-template-columns: 1fr;
    grid-template-rows: auto 1fr auto;
    height: auto;
  }
  .presets-panel, .search-panel {
    border: none;
    border-bottom: 1px solid var(--border);
    max-height: 200px;
  }
  .visualizer-section { min-height: 60vh; }
}