/* =============================================
   T₂ CALCULATOR — STYLESHEET
   ============================================= */

:root {
  --bg:           #080c10;
  --bg-panel:     #0d1218;
  --bg-panel-2:   #111820;
  --bg-card:      #131b24;
  --bg-card-2:    #171f2a;
  --border:       rgba(0, 212, 170, 0.12);
  --border-light: rgba(255, 255, 255, 0.06);
  --accent:       #00d4aa;
  --accent-dim:   rgba(0, 212, 170, 0.15);
  --accent-glow:  rgba(0, 212, 170, 0.25);
  --accent2:      #3b8fff;
  --accent2-dim:  rgba(59, 143, 255, 0.12);
  --text:         #e8edf2;
  --text-2:       #8a9bac;
  --text-3:       #526170;
  --red:          #ff5757;
  --red-dim:      rgba(255, 87, 87, 0.12);
  --font-heading: 'Syne', sans-serif;
  --font-body:    'DM Sans', sans-serif;
  --font-mono:    'DM Mono', monospace;
  --radius:       12px;
  --radius-sm:    8px;
  --shadow:       0 4px 32px rgba(0,0,0,0.5);
  --shadow-accent: 0 0 40px rgba(0, 212, 170, 0.12);
}

*, *::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: 15px;
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

.bg-lattice {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  opacity: 0.35;
}
#latticeCanvas { width: 100%; height: 100%; }

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: var(--accent-dim);
  color: var(--accent);
  padding: 0.1em 0.4em;
  border-radius: 4px;
}

/* ── Header ── */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(8, 12, 16, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-light);
}
.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 2rem;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.logo { display: flex; align-items: center; gap: 12px; text-decoration: none; }
.logo-icon { width: 36px; height: 36px; flex-shrink: 0; }
.logo-text { display: flex; flex-direction: column; gap: 1px; }
.logo-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1rem;
  color: var(--text);
  letter-spacing: -0.02em;
  line-height: 1;
}
.logo-sub {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--text-3);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  line-height: 1;
}
.header-nav { display: flex; align-items: center; gap: 0.25rem; }
.nav-link {
  font-family: var(--font-body);
  font-size: 0.875rem;
  color: var(--text-2);
  text-decoration: none;
  padding: 0.4rem 0.875rem;
  border-radius: var(--radius-sm);
  transition: color 0.2s, background 0.2s;
  display: flex;
  align-items: center;
  gap: 6px;
}
.nav-link:hover { color: var(--text); background: var(--bg-card); }
.nav-github { border: 1px solid var(--border-light); margin-left: 0.5rem; }
.nav-github:hover { border-color: var(--border); }

/* ── Hero ── */
.hero {
  position: relative;
  z-index: 1;
  padding: 5rem 2rem 3rem;
  text-align: center;
}
.hero-inner {
  max-width: 720px;
  margin: 0 auto;
  animation: fadeUp 0.7s ease both;
}
.hero-badge {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--border);
  padding: 0.3rem 0.9rem;
  border-radius: 100px;
  margin-bottom: 1.75rem;
  background: var(--accent-dim);
}

/* CHANGE 2: Hero title uses DM Sans (body font) instead of Syne */
.hero-title {
  font-family: var(--font-body);
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 500;
  line-height: 1.2;
  letter-spacing: -0.01em;
  color: var(--text);
  margin-bottom: 1.25rem;
}
.hero-accent {
  color: var(--accent);
  font-weight: 500;
  position: relative;
}
.hero-accent::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0; right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--accent), transparent);
  border-radius: 2px;
}
.hero-desc {
  font-size: 1rem;
  color: var(--text-2);
  max-width: 520px;
  margin: 0 auto 2.5rem;
  line-height: 1.7;
}
.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.5rem;
  animation: fadeUp 0.7s 0.15s ease both;
}
.stat-item { display: flex; flex-direction: column; align-items: center; gap: 4px; }
.stat-value { font-family: var(--font-mono); font-size: 0.9rem; font-weight: 500; color: var(--accent); }
.stat-label { font-size: 0.72rem; color: var(--text-3); letter-spacing: 0.04em; }
.stat-divider { width: 1px; height: 32px; background: var(--border-light); }

/* ── Main App ── */
.app-main {
  position: relative;
  z-index: 1;
  padding: 1rem 2rem 5rem;
}
.app-container {
  max-width: 780px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

/* ── Panel ── */
.panel {
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 2rem;
  position: relative;
  overflow: hidden;
  animation: fadeUp 0.6s ease both;
}
.panel::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border), transparent);
}
.panel-header {
  margin-bottom: 1.75rem;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
}
.panel-title {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
  display: flex;
  align-items: center;
  gap: 10px;
  line-height: 1.2;
}
.panel-num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--accent);
  letter-spacing: 0.08em;
  background: var(--accent-dim);
  padding: 0.2em 0.5em;
  border-radius: 4px;
  border: 1px solid var(--border);
}
.panel-desc { font-size: 0.875rem; color: var(--text-3); margin-top: 0.4rem; }

/* ── Drop Zone ── */
.drop-zone {
  border: 1.5px dashed var(--border);
  border-radius: var(--radius);
  padding: 3rem 2rem;
  text-align: center;
  cursor: pointer;
  transition: border-color 0.25s, background 0.25s, box-shadow 0.25s;
  position: relative;
  overflow: hidden;
  background: var(--bg-card);
  min-height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.drop-zone:hover, .drop-zone:focus, .drop-zone.drag-over {
  border-color: var(--accent);
  background: var(--accent-dim);
  box-shadow: var(--shadow-accent);
  outline: none;
}
.drop-zone.drag-over { border-style: solid; }
.drop-zone-content { display: flex; flex-direction: column; align-items: center; gap: 0.6rem; }
.drop-icon {
  width: 64px; height: 64px;
  color: var(--text-3);
  margin-bottom: 0.5rem;
  transition: color 0.25s, transform 0.25s;
}
.drop-zone:hover .drop-icon, .drop-zone.drag-over .drop-icon {
  color: var(--accent);
  transform: translateY(-4px);
}
.drop-primary { font-size: 0.95rem; font-weight: 500; color: var(--text-2); }
.drop-secondary { font-size: 0.875rem; color: var(--text-3); }
.drop-hint {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-3);
  letter-spacing: 0.04em;
  margin-top: 0.5rem;
}
.browse-btn {
  background: none; border: none; color: var(--accent); cursor: pointer;
  font: inherit; font-size: 0.875rem; text-decoration: underline;
  text-underline-offset: 2px; padding: 0; transition: opacity 0.2s;
}
.browse-btn:hover { opacity: 0.75; }

/* CHANGE 5: file list in drop zone */
.drop-zone-ready {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 0.75rem;
  width: 100%;
  padding: 0.5rem;
  animation: fadeIn 0.3s ease;
}
.file-list {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  max-height: 220px;
  overflow-y: auto;
}
.file-list::-webkit-scrollbar { width: 4px; }
.file-list::-webkit-scrollbar-track { background: transparent; }
.file-list::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.file-list-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background: var(--bg-card-2);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  padding: 0.6rem 0.875rem;
}
.file-list-icon { color: var(--accent); flex-shrink: 0; }
.file-list-info { flex: 1; text-align: left; min-width: 0; }
.file-list-name {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.file-list-size { font-size: 0.72rem; color: var(--text-3); margin-top: 1px; }
.file-list-status {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  padding: 0.15em 0.5em;
  border-radius: 4px;
  flex-shrink: 0;
}
.file-list-status.pending  { background: var(--accent-dim);  color: var(--accent); }
.file-list-status.loading  { background: rgba(59,143,255,0.12); color: var(--accent2); }
.file-list-status.done     { background: rgba(0,212,170,0.12); color: var(--accent); }
.file-list-status.error    { background: var(--red-dim); color: var(--red); }

.file-remove-all {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  color: var(--text-3);
  font-family: var(--font-body);
  font-size: 0.78rem;
  cursor: pointer;
  padding: 0.45rem 0.875rem;
  transition: color 0.2s, border-color 0.2s;
  align-self: flex-end;
}
.file-remove-all:hover { color: var(--red); border-color: var(--red); }

/* ── Error ── */
/* ── Ensures HTML 'hidden' attribute always wins over CSS display rules ── */
[hidden] { display: none !important; }

.error-msg {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--red-dim);
  border: 1px solid rgba(255,87,87,0.25);
  border-radius: var(--radius-sm);
  padding: 0.75rem 1rem;
  color: var(--red);
  font-size: 0.875rem;
  margin-top: 1rem;
  animation: fadeIn 0.3s ease;
}

/* ── Compute Button ── */
.compute-btn {
  position: relative;
  margin-top: 1.5rem;
  width: 100%;
  padding: 0.9rem 1.5rem;
  background: linear-gradient(135deg, var(--accent) 0%, #00b890 100%);
  color: #080c10;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1rem;
  letter-spacing: 0.01em;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
  overflow: hidden;
  transition: opacity 0.25s, transform 0.2s, box-shadow 0.25s;
  box-shadow: 0 4px 24px rgba(0,212,170,0.25);
}
.compute-btn:not(:disabled):hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0,212,170,0.35);
}
.compute-btn:not(:disabled):active { transform: translateY(0); }
.compute-btn:disabled { opacity: 0.35; cursor: not-allowed; box-shadow: none; }
.compute-btn-inner {
  position: relative; z-index: 1;
  display: flex; align-items: center; justify-content: center; gap: 8px;
}
.btn-shimmer {
  position: absolute; inset: 0;
  background: linear-gradient(105deg, transparent 40%, rgba(255,255,255,0.2) 50%, transparent 60%);
  background-size: 200% 100%;
  animation: shimmer 3s infinite;
}
.compute-btn:disabled .btn-shimmer { display: none; }

/* ── Loading ── */
.loading-state {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  margin-top: 1.5rem;
  padding: 1.25rem 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  animation: fadeIn 0.3s ease;
}
.spinner-ring {
  width: 36px; height: 36px;
  border: 2px solid var(--border-light);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  flex-shrink: 0;
}
.loading-primary { font-size: 0.9rem; font-weight: 500; color: var(--text); }
.loading-secondary {
  font-family: var(--font-mono); font-size: 0.75rem; color: var(--accent);
  margin-top: 2px; transition: opacity 0.3s;
}

/* ── Results Panel ── */
.results-panel { animation: fadeUp 0.5s ease both; }
.reset-btn {
  display: flex; align-items: center; gap: 6px;
  background: var(--bg-card); border: 1px solid var(--border-light);
  border-radius: var(--radius-sm); color: var(--text-2);
  font-family: var(--font-body); font-size: 0.8rem;
  cursor: pointer; padding: 0.4rem 0.8rem;
  transition: color 0.2s, border-color 0.2s;
  white-space: nowrap; flex-shrink: 0;
}
.reset-btn:hover { color: var(--text); border-color: var(--border); }

/* CHANGE 5: individual result card per file */
.result-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  margin-bottom: 1.25rem;
  overflow: hidden;
  animation: fadeUp 0.4s ease both;
}
.result-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.875rem 1.25rem;
  border-bottom: 1px solid var(--border-light);
  background: var(--bg-card-2);
}
.result-card-filename {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--accent);
  font-weight: 500;
}
.result-card-index {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: var(--text-3);
  letter-spacing: 0.08em;
}
.result-card-body { padding: 1.25rem; }

/* T2 hero inside each card */
.t2-hero {
  background: linear-gradient(135deg, rgba(0,212,170,0.08), rgba(0,212,170,0.03));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-align: center;
  margin-bottom: 1.25rem;
  position: relative;
  overflow: hidden;
}
.t2-hero::before {
  content: '';
  position: absolute; top: -60px; left: 50%; transform: translateX(-50%);
  width: 200px; height: 120px;
  background: radial-gradient(ellipse, rgba(0,212,170,0.15), transparent 70%);
  pointer-events: none;
}
.t2-label {
  font-family: var(--font-mono); font-size: 0.72rem;
  letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 0.75rem;
}
.t2-value-wrap {
  display: flex; align-items: baseline;
  justify-content: center; gap: 0.5rem; margin-bottom: 0.5rem;
}
.t2-value {
  font-family: var(--font-heading);
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800; color: var(--accent);
  letter-spacing: -0.04em; line-height: 1;
}
.t2-unit { font-family: var(--font-mono); font-size: 1.1rem; color: var(--text-2); }
.t2-desc { font-size: 0.8rem; color: var(--text-3); }

/* Info grid */
.info-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}
.info-card {
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  padding: 0.875rem 1rem;
  animation: fadeIn 0.4s ease both;
}
.info-card-label {
  font-family: var(--font-mono); font-size: 0.68rem;
  letter-spacing: 0.1em; text-transform: uppercase;
  color: var(--text-3); margin-bottom: 0.3rem;
}
.info-card-value { font-family: var(--font-mono); font-size: 0.9rem; color: var(--text); font-weight: 500; }
.formula-value { font-size: 1rem; color: var(--accent2); letter-spacing: 0.02em; }

/* Lattice */
.section-subtitle {
  font-family: var(--font-mono); font-size: 0.72rem;
  letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--text-3); margin-bottom: 0.75rem;
}
.lattice-section { margin-bottom: 1.25rem; }
.lattice-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 0.5rem;
}
.lattice-card {
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  padding: 0.65rem 0.4rem;
  text-align: center;
  display: flex; flex-direction: column; align-items: center; gap: 3px;
}
.lattice-sym { font-family: 'Georgia', serif; font-style: italic; font-size: 0.95rem; color: var(--accent2); line-height: 1; }
.lattice-val { font-family: var(--font-mono); font-size: 0.78rem; color: var(--text); font-weight: 500; }
.lattice-unit { font-family: var(--font-mono); font-size: 0.6rem; color: var(--text-3); }

/* Raw JSON */
.raw-section { border-top: 1px solid var(--border-light); padding-top: 1rem; margin-top: 0.5rem; }
.raw-toggle {
  background: none; border: none; color: var(--text-2);
  font-family: var(--font-mono); font-size: 0.78rem;
  cursor: pointer; display: flex; align-items: center;
  gap: 8px; padding: 0.5rem 0;
  transition: color 0.2s; letter-spacing: 0.02em;
}
.raw-toggle:hover { color: var(--accent); }
.raw-toggle .chevron { transition: transform 0.25s; margin-left: auto; }
.raw-toggle[aria-expanded="true"] .chevron { transform: rotate(180deg); }
.raw-content { margin-top: 0.75rem; animation: fadeIn 0.3s ease; }
.raw-json {
  background: var(--bg); border: 1px solid var(--border-light);
  border-radius: var(--radius-sm); padding: 1.25rem;
  font-family: var(--font-mono); font-size: 0.78rem;
  line-height: 1.7; color: var(--accent);
  white-space: pre-wrap; word-break: break-all;
  max-height: 320px; overflow-y: auto;
}
.raw-json::-webkit-scrollbar { width: 4px; }
.raw-json::-webkit-scrollbar-track { background: transparent; }
.raw-json::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.download-row {
  display: flex;
  gap: 0.6rem;
  margin-top: 1.25rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--border-light);
}
.download-btn {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-light);
  background: var(--bg-card);
  color: var(--text-2);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.03em;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s, background 0.2s;
}
.download-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-dim);
}
.download-btn-excel:hover {
  border-color: #1d7a45;
  color: #2db86a;
  background: rgba(29, 122, 69, 0.12);
}

/* ── About ── */
.about-section {
  position: relative; z-index: 1;
  padding: 5rem 2rem;
  border-top: 1px solid var(--border-light);
  background: var(--bg-panel);
}
.about-inner { max-width: 1100px; margin: 0 auto; }

/* Section titles — DM Sans to match hero title */
.about-title, .ack-title, .theory-title {
  font-family: var(--font-body);
  font-size: clamp(1.5rem, 3vw, 1.9rem);
  font-weight: 500;
  letter-spacing: -0.01em;
  text-align: center;   /* (3) centers Acknowledgements title */
  color: var(--text);
  margin-bottom: 3rem;
}

.steps-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.25rem; margin-bottom: 0; }
.step-card {
  background: var(--bg-card); border: 1px solid var(--border-light);
  border-radius: var(--radius); padding: 1.5rem 1.25rem;
  transition: border-color 0.25s, transform 0.25s;
}
.step-card:hover { border-color: var(--border); transform: translateY(-4px); }
.step-num {
  font-family: var(--font-mono); font-size: 0.7rem;
  letter-spacing: 0.1em; color: var(--accent);
  background: var(--accent-dim); padding: 0.2em 0.6em;
  border-radius: 4px; display: inline-block; margin-bottom: 0.875rem;
}
.step-card h3 {
  font-family: var(--font-heading); font-size: 0.95rem;
  font-weight: 700; margin-bottom: 0.5rem; letter-spacing: -0.01em;
}
.step-card p { font-size: 0.83rem; color: var(--text-2); line-height: 1.65; }

/* CHANGE 2: Theory section below the step cards */
.theory-section {
  margin-top: 3.5rem;
  border-top: 1px solid var(--border-light);
  padding-top: 3rem;
}
.theory-title {
  font-family: var(--font-body);
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 1.25rem;
  letter-spacing: -0.01em;
  max-width: 820px;
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}
.theory-body {
  font-size: 0.9rem;
  color: var(--text-2);
  line-height: 1.8;
  max-width: 820px;
  margin-left: auto;
  margin-right: auto;
}
.theory-body p { margin-bottom: 1rem; }
.theory-body p:last-child { margin-bottom: 0; }
.theory-body a { color: var(--accent); text-decoration: underline; text-underline-offset: 2px; }
.theory-body strong { color: var(--text); font-weight: 500; }

/* (1) Indented bullet points */
.theory-body ul, .theory-body ol {
  margin: 0.75rem 0 1rem 2rem;
  padding: 0;
}
.theory-body li {
  margin-bottom: 0.55rem;
  line-height: 1.75;
}
.theory-body li:last-child { margin-bottom: 0; }

/* Citation superscript links */
.cite-link, .cite-link-nohover {
  color: var(--accent);
  text-decoration: none;
  font-size: 0.78em;
  vertical-align: super;
  line-height: 0;
  font-family: var(--font-mono);
  padding: 0 1px;
}
.cite-link { transition: opacity 0.2s; }
.cite-link:hover { opacity: 0.7; text-decoration: underline; }

/* References block */
.theory-references {
  margin-top: 2.5rem;
  padding-top: 1.75rem;
  border-top: 1px solid var(--border-light);
}
.theory-references-title {
  font-family: var(--font-body);
  font-size: 1rem;
  font-weight: 500;
  color: var(--text);
  margin-bottom: 0.75rem;
  letter-spacing: -0.01em;
}
/* (2) References label stays flush-left; numbered items are indented */
.theory-references ol {
  list-style: decimal;
  margin: 0 0 0 2rem;  /* indent the list without moving the label */
  padding: 0;
}
.theory-references li {
  font-size: 0.83rem;
  color: var(--text-3);
  line-height: 1.65;
  margin-bottom: 0.6rem;
  scroll-margin-top: 80px;
}
.theory-references li a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 2px;
}
.theory-references li a:hover { opacity: 0.75; }

/* (4) Dimensionality selector */
.dim-selector-wrap {
  margin-top: 0;
  margin-bottom: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.dim-selector-label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-3);
}
.dim-selector-pills {
  display: flex;
  gap: 0.5rem;
}
.dim-pill {
  flex: 1;
  padding: 0.6rem 1rem;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border-light);
  background: var(--bg-card);
  color: var(--text-2);
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: border-color 0.2s, background 0.2s, color 0.2s;
  text-align: center;
}
.dim-pill:hover {
  border-color: var(--border);
  color: var(--text);
}
.dim-pill.selected {
  border-color: var(--accent);
  background: var(--accent-dim);
  color: var(--accent);
}
.dim-pill-sub {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--text-3);
  margin-top: 2px;
  letter-spacing: 0.04em;
}
.dim-pill.selected .dim-pill-sub { color: var(--accent); opacity: 0.7; }

/* Heterostructure pill uses accent2 when selected */
#pillHetero.selected {
  border-color: var(--accent2);
  background: var(--accent2-dim);
  color: var(--accent2);
}
#pillHetero.selected .dim-pill-sub { color: var(--accent2); opacity: 0.7; }

/* ── Heterostructure dual drop zones ── */
.hetero-zones {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
.hetero-zone-col {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.hetero-zone-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.hetero-zone-title {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-3);
}
.hetero-badge {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  font-weight: 500;
  padding: 0.1em 0.5em;
  border-radius: 4px;
  letter-spacing: 0.06em;
}
.hetero-badge-2d {
  background: var(--accent-dim);
  color: var(--accent);
  border: 1px solid var(--border);
}
.hetero-badge-3d {
  background: var(--accent2-dim);
  color: var(--accent2);
  border: 1px solid rgba(59,143,255,0.2);
}
/* Smaller padding for hetero drop zones so they fit side-by-side */
.hetero-drop {
  padding: 1.5rem 1rem;
  min-height: 160px;
}
/* 3D drop zone accent uses --accent2 */
.hetero-drop-3d { border-color: rgba(59,143,255,0.15); }
.hetero-drop-3d:hover,
.hetero-drop-3d.drag-over { border-color: var(--accent2); }
.drop-icon-sm svg { width: 44px; height: 44px; }

@media (max-width: 600px) {
  .hetero-zones { grid-template-columns: 1fr; }
}
  display: flex;
  flex-wrap: wrap;
  gap: 1.5rem;
  margin: 2rem 0;
}
.theory-figure {
  flex: 1 1 280px;
  max-width: 480px;
}
.theory-figure img {
  width: 100%;
  height: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-light);
  display: block;
}
.theory-figure figcaption {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--text-3);
  margin-top: 0.6rem;
  line-height: 1.5;
  letter-spacing: 0.02em;
}

/* ── CHANGE 1: Acknowledgements — same style as About section ── */
.acknowledgements-section {
  position: relative;
  z-index: 1;
  padding: 4rem 2rem;
  border-top: 1px solid var(--border-light);
  background: var(--bg-panel);
}
.ack-inner { max-width: 820px; margin: 0 auto; }
/* .ack-title shares styles with .about-title above */
.ack-desc {
  font-size: 0.92rem;
  color: var(--text-2);
  line-height: 1.8;
  text-align: left;
}
.ack-desc a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 2px;
  transition: opacity 0.2s;
}
.ack-desc a:hover { opacity: 0.75; }

/* ── Footer ── */
.site-footer {
  position: relative; z-index: 1;
  border-top: 1px solid var(--border-light);
  padding: 2rem; text-align: center;
}
.footer-inner { max-width: 1100px; margin: 0 auto; }
.footer-logo { font-family: var(--font-heading); font-size: 1rem; font-weight: 700; color: var(--text-3); margin-bottom: 0.35rem; }
.footer-copy { font-family: var(--font-mono); font-size: 0.72rem; color: var(--text-3); letter-spacing: 0.06em; }

/* ── Animations ── */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(20px); }
  to   { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
  from { opacity: 0; } to { opacity: 1; }
}
@keyframes spin { to { transform: rotate(360deg); } }
@keyframes shimmer {
  0%   { background-position: 200% center; }
  100% { background-position: -200% center; }
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .header-inner { padding: 0 1rem; }
  .hero { padding: 3.5rem 1rem 2rem; }
  .app-main { padding: 1rem 1rem 4rem; }
  .panel { padding: 1.5rem; }
  .info-grid { grid-template-columns: 1fr 1fr; gap: 0.6rem; }
  .lattice-grid { grid-template-columns: repeat(3, 1fr); }
  .steps-grid { grid-template-columns: 1fr 1fr; }
  .panel-header { flex-direction: column; align-items: flex-start; }
  .theory-figures { flex-direction: column; }
  .theory-figure { max-width: 100%; }
}
@media (max-width: 480px) {
  .hero-title { font-size: 1.75rem; }
  .header-nav .nav-link:not(.nav-github) { display: none; }
  .lattice-grid { grid-template-columns: repeat(2, 1fr); }
  .steps-grid { grid-template-columns: 1fr; }
  .info-grid { grid-template-columns: 1fr; }
}