/* MathLens - Deep Space Scientific Theme */
:root {
  --bg-0: #05060d;
  --bg-1: #0a0c18;
  --bg-2: #121629;
  --panel: rgba(18, 22, 41, 0.55);
  --panel-border: rgba(120, 160, 255, 0.15);
  --panel-glow: rgba(90, 130, 255, 0.08);
  --accent: #7aa8ff;
  --accent-2: #a878ff;
  --accent-3: #46e0d5;
  --accent-warn: #ffb457;
  --text-0: #eef2ff;
  --text-1: #b8c1e0;
  --text-2: #6c749a;
  --text-3: #3a4166;
  --success: #46e0d5;
  --line: rgba(140, 170, 255, 0.12);
  --line-strong: rgba(140, 170, 255, 0.28);
  --shadow-lg: 0 20px 60px rgba(0,0,0,0.5), 0 0 40px rgba(90,130,255,0.05);
  --radius: 14px;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', 'Menlo', monospace;
  --font-sans: 'Inter', -apple-system, 'PingFang SC', 'Microsoft YaHei', system-ui, sans-serif;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  color: var(--text-0);
  background:
    radial-gradient(ellipse at 20% 0%, rgba(90,130,255,0.15), transparent 50%),
    radial-gradient(ellipse at 80% 100%, rgba(168,120,255,0.12), transparent 50%),
    linear-gradient(180deg, var(--bg-0) 0%, var(--bg-1) 100%);
  overflow-x: hidden;
  letter-spacing: 0.01em;
}

#bg-canvas {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  z-index: 0;
  pointer-events: none;
  opacity: 0.55;
}

/* Topbar */
.topbar {
  position: relative;
  z-index: 5;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 22px 40px 18px;
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(20px) saturate(1.2);
  background: linear-gradient(180deg, rgba(5,6,13,0.6), rgba(5,6,13,0.15));
}

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

.logo-mark {
  width: 36px; height: 36px;
  border-radius: 10px;
  background:
    conic-gradient(from 210deg, #7aa8ff, #a878ff, #46e0d5, #7aa8ff);
  position: relative;
  box-shadow: 0 0 24px rgba(122,168,255,0.5);
  animation: spin 12s linear infinite;
}
.logo-mark::before {
  content: '';
  position: absolute; inset: 4px;
  border-radius: 7px;
  background: var(--bg-0);
}
.logo-mark::after {
  content: '∫';
  position: absolute; inset: 0;
  display: grid; place-items: center;
  font-family: 'Times New Roman', serif;
  font-size: 22px;
  color: var(--accent);
  font-weight: 300;
}
@keyframes spin { to { transform: rotate(360deg); } }

.brand-title {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: 0.08em;
  background: linear-gradient(90deg, #eef2ff, #7aa8ff);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.brand-sub {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-2);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-top: 2px;
}


/* Mode Switch */
.mode-switch {
  display: flex;
  gap: 4px;
  padding: 4px;
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 12px;
  backdrop-filter: blur(10px);
}
.mode-switch button {
  background: transparent;
  border: none;
  color: var(--text-1);
  font-family: var(--font-sans);
  font-size: 13px;
  padding: 8px 18px;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.25s cubic-bezier(.4,0,.2,1);
  letter-spacing: 0.02em;
}
.mode-switch button:hover { color: var(--text-0); background: rgba(122,168,255,0.08); }
.mode-switch button.active {
  color: var(--text-0);
  background: linear-gradient(135deg, rgba(122,168,255,0.25), rgba(168,120,255,0.2));
  box-shadow: inset 0 0 0 1px rgba(122,168,255,0.35), 0 4px 12px rgba(122,168,255,0.15);
}

/* Workspace */
.workspace {
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: minmax(320px, 380px) 1fr minmax(340px, 420px);
  gap: 20px;
  padding: 24px 32px;
  min-height: calc(100vh - 130px);
}

.panel {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: var(--radius);
  padding: 22px 22px 20px;
  backdrop-filter: blur(20px) saturate(1.1);
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  gap: 16px;
  position: relative;
  overflow: hidden;
}

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

.panel-head {
  display: flex;
  align-items: center;
  gap: 10px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}
.panel-idx {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--accent);
  background: rgba(122,168,255,0.1);
  padding: 3px 8px;
  border-radius: 5px;
  letter-spacing: 0.1em;
}
.panel-head h2 {
  margin: 0;
  font-size: 15px;
  font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--text-0);
}
.viz-status {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-2);
  padding: 4px 10px;
  border: 1px solid var(--line);
  border-radius: 20px;
}
.viz-status.running { color: var(--accent-warn); border-color: rgba(255,180,87,0.35); }
.viz-status.done { color: var(--accent-3); border-color: rgba(70,224,213,0.35); }
.viz-status.error { color: #ff6b8a; border-color: rgba(255,107,138,0.35); }

/* Input area */
.input-block { display: flex; flex-direction: column; gap: 10px; }
.input-block.hidden { display: none; }

.field-label {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--text-2);
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.expr-input {
  background: rgba(5, 6, 13, 0.6);
  border: 1px solid var(--line);
  color: var(--text-0);
  font-family: var(--font-mono);
  font-size: 15px;
  padding: 12px 14px;
  border-radius: 10px;
  outline: none;
  transition: border-color 0.25s, box-shadow 0.25s;
  width: 100%;
  resize: none;
}
.expr-input:focus {
  border-color: rgba(122,168,255,0.5);
  box-shadow: 0 0 0 3px rgba(122,168,255,0.12);
}
.matrix-input { min-height: 100px; line-height: 1.6; }

.examples { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; }
.examples > span { font-size: 11px; color: var(--text-2); margin-right: 4px; }
.chip {
  background: rgba(122,168,255,0.06);
  border: 1px solid var(--line);
  color: var(--text-1);
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 4px 10px;
  border-radius: 20px;
  cursor: pointer;
  transition: all 0.2s;
}
.chip:hover {
  background: rgba(122,168,255,0.18);
  color: var(--text-0);
  border-color: rgba(122,168,255,0.4);
  transform: translateY(-1px);
}

.range-block { display: flex; flex-direction: column; gap: 8px; }
.range-row {
  display: flex; align-items: center; gap: 8px;
  font-size: 12px; color: var(--text-2);
}
.range-row label { min-width: 50px; font-family: var(--font-mono); }
.range-row.hidden { display: none; }
.range-row input {
  width: 60px;
  background: rgba(5,6,13,0.6);
  border: 1px solid var(--line);
  color: var(--text-0);
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 6px 8px;
  border-radius: 6px;
  outline: none;
}
.range-row input:focus { border-color: rgba(122,168,255,0.5); }


/* Run button */
.run-btn {
  position: relative;
  margin-top: auto;
  border: none;
  background: linear-gradient(135deg, #4a72d8 0%, #7c4ad8 100%);
  color: #fff;
  font-family: var(--font-sans);
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.08em;
  padding: 14px 24px;
  border-radius: 10px;
  cursor: pointer;
  overflow: hidden;
  transition: transform 0.2s, box-shadow 0.25s;
  box-shadow: 0 8px 24px rgba(90,120,220,0.35), inset 0 1px 0 rgba(255,255,255,0.15);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
}
.run-btn:hover { transform: translateY(-1px); box-shadow: 0 12px 32px rgba(90,120,220,0.5), inset 0 1px 0 rgba(255,255,255,0.2); }
.run-btn:active { transform: translateY(0); }
.run-btn-arrow { font-size: 18px; transition: transform 0.25s; }
.run-btn:hover .run-btn-arrow { transform: translateX(4px); }
.run-btn-glow {
  position: absolute;
  inset: -50%;
  background: radial-gradient(circle at center, rgba(255,255,255,0.3), transparent 60%);
  opacity: 0;
  transition: opacity 0.3s;
  pointer-events: none;
}
.run-btn:hover .run-btn-glow { opacity: 1; animation: sweep 1.5s linear infinite; }
@keyframes sweep {
  0% { transform: translateX(-30%) translateY(-30%); }
  100% { transform: translateX(30%) translateY(30%); }
}
.run-btn.running { opacity: 0.7; pointer-events: none; }

/* Viz panel */
.panel-viz { min-height: 620px; }
.plot-area {
  flex: 1;
  min-height: 460px;
  background: rgba(5,6,13,0.4);
  border: 1px solid var(--line);
  border-radius: 10px;
  overflow: hidden;
  position: relative;
}
.latex-display {
  min-height: 60px;
  padding: 14px 18px;
  background: rgba(5,6,13,0.5);
  border: 1px solid var(--line);
  border-radius: 10px;
  color: var(--text-0);
  font-size: 15px;
  display: flex; align-items: center; justify-content: center;
  overflow-x: auto;
}

/* Info panel */
.tab-head {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--line);
  padding-bottom: 0;
  margin-bottom: 4px;
}
.tab-btn {
  background: transparent;
  border: none;
  color: var(--text-2);
  font-family: var(--font-sans);
  font-size: 13px;
  padding: 8px 4px;
  margin-right: 18px;
  cursor: pointer;
  position: relative;
  transition: color 0.2s;
  letter-spacing: 0.03em;
}
.tab-btn::after {
  content: '';
  position: absolute;
  left: 0; right: 0; bottom: -1px;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  border-radius: 2px;
  transform: scaleX(0);
  transform-origin: left;
  transition: transform 0.3s cubic-bezier(.4,0,.2,1);
}
.tab-btn:hover { color: var(--text-1); }
.tab-btn.active { color: var(--text-0); }
.tab-btn.active::after { transform: scaleX(1); }

.tab-body { flex: 1; overflow-y: auto; padding-right: 4px; }
.tab-pane { display: none; animation: fadeUp 0.35s cubic-bezier(.4,0,.2,1); }
.tab-pane.active { display: block; }

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.hint {
  color: var(--text-2);
  font-size: 13px;
  text-align: center;
  padding: 40px 20px;
  font-style: italic;
}

/* Concept cards */
.concept-card {
  background: linear-gradient(135deg, rgba(122,168,255,0.05), rgba(168,120,255,0.03));
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 10px;
  padding: 14px 16px;
  margin-bottom: 10px;
  transition: all 0.3s cubic-bezier(.4,0,.2,1);
  animation: slideIn 0.4s cubic-bezier(.4,0,.2,1) backwards;
}
.concept-card:nth-child(1) { animation-delay: 0.05s; }
.concept-card:nth-child(2) { animation-delay: 0.12s; }
.concept-card:nth-child(3) { animation-delay: 0.19s; }
.concept-card:nth-child(4) { animation-delay: 0.26s; }
.concept-card:nth-child(5) { animation-delay: 0.33s; }

.concept-card:hover {
  border-left-color: var(--accent-2);
  transform: translateX(4px);
  background: linear-gradient(135deg, rgba(122,168,255,0.09), rgba(168,120,255,0.05));
}

@keyframes slideIn {
  from { opacity: 0; transform: translateX(-12px); }
  to { opacity: 1; transform: translateX(0); }
}

.concept-title {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-0);
  margin-bottom: 6px;
  display: flex; align-items: center; gap: 8px;
}
.concept-tag {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--accent);
  background: rgba(122,168,255,0.12);
  padding: 2px 6px;
  border-radius: 4px;
  letter-spacing: 0.08em;
}
.concept-desc {
  font-size: 12.5px;
  color: var(--text-1);
  line-height: 1.7;
}
.concept-formula {
  margin-top: 8px;
  padding: 8px 10px;
  background: rgba(5,6,13,0.5);
  border-radius: 6px;
  font-size: 13px;
  color: var(--text-0);
  overflow-x: auto;
}

/* Solve pane result */
.result-block { margin-bottom: 14px; }
.result-label {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-2);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  margin-bottom: 6px;
}
.result-value {
  background: rgba(5,6,13,0.55);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 10px 14px;
  font-size: 14px;
  color: var(--text-0);
  overflow-x: auto;
}
.result-value.big { font-size: 15px; }

/* Steps */
.step-item {
  display: flex;
  gap: 12px;
  padding: 12px 0;
  border-bottom: 1px solid var(--line);
  animation: slideIn 0.4s cubic-bezier(.4,0,.2,1) backwards;
}
.step-item:last-child { border-bottom: none; }
.step-num {
  flex-shrink: 0;
  width: 26px; height: 26px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: grid; place-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  color: #fff;
  font-weight: 600;
}
.step-body { flex: 1; }
.step-title { font-size: 13.5px; color: var(--text-0); margin-bottom: 4px; }
.step-desc { font-size: 12.5px; color: var(--text-1); line-height: 1.6; }
.step-desc mjx-container { color: var(--text-0); }

.footer {
  position: relative;
  z-index: 2;
  text-align: center;
  padding: 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--text-3);
  letter-spacing: 0.1em;
}

/* Scrollbars */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(122,168,255,0.15); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(122,168,255,0.35); }

/* Responsive */
@media (max-width: 1200px) {
  .workspace { grid-template-columns: 1fr; }
  .panel-viz { min-height: 500px; }
}
@media (max-width: 640px) {
  .topbar { flex-direction: column; gap: 12px; padding: 16px 20px; }
  .workspace { padding: 16px; gap: 14px; }
  .mode-switch button { padding: 6px 12px; font-size: 12px; }
}