:root {
  --bg: #ffffff;
  --text-main: #111111;
  --text-muted: #555555;
  --accent: #0055aa;
  --border: #e0e0e0;
  --font-sans: "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-mono: "SFMono-Regular", Consolas, "Courier New", monospace;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text-main);
  font-family: var(--font-sans);
  line-height: 1.6;
  font-size: 15px;
  max-width: 800px;
  margin: 40px auto;
  padding: 0 20px;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ── Header ── */
header {
  margin-bottom: 3rem;
  border-left: 4px solid var(--text-main);
  padding-left: 20px;
}
h1 { font-size: 2.2rem; font-weight: 600; margin-bottom: 0.2rem; letter-spacing: -0.5px; }

.contact-bar {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 1.2rem;
}
.abstract { font-size: 1.05rem; color: var(--text-main); max-width: 700px; }

/* ── Sections ── */
section { margin-bottom: 3.5rem; }

h2.section-title {
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  border-bottom: 2px solid var(--text-main);
  padding-bottom: 0.4rem;
  margin-bottom: 1.8rem;
}

/* ── Shared project bits ── */
.tech-stack {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--accent);
  margin-bottom: 0.8rem;
  text-transform: uppercase;
}

ul.project-bullets { margin-left: 20px; color: var(--text-muted); font-size: 0.92rem; }
ul.project-bullets li { margin-bottom: 0.6rem; }
ul.project-bullets strong { color: var(--text-main); font-weight: 600; }

.project-links { margin-top: 0.8rem; margin-bottom: 1.2rem; }

.btn-link {
  display: inline-block;
  background: var(--text-main);
  color: #ffffff !important;
  padding: 6px 14px;
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-decoration: none;
  transition: background 0.2s;
}
.btn-link:hover { background: var(--text-muted); text-decoration: none; }

/* ── INDEX: Project Cards — 2-column square grid ── */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}

.project-card {
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
  background: #fafafa;
  transition: box-shadow 0.2s;
  display: flex;
  flex-direction: column;
}
.project-card:hover { box-shadow: 0 3px 14px rgba(0,0,0,0.08); }

/* Square viewer — aspect-ratio forces height = width */
.card-viewer {
  width: 100%;
  aspect-ratio: 1 / 1;
  background: #f0f0f0;
  position: relative;
  overflow: hidden;
  flex-shrink: 0;
}
.card-viewer model-viewer {
  width: 100%;
  height: 100%;
  outline: none;
  display: block;
}

/* Firmware placeholder — exactly same square size */
.card-viewer-placeholder {
  width: 100%;
  aspect-ratio: 1 / 1;
  background: #0f172a;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-shrink: 0;
}
.card-viewer-placeholder .fw-label {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  letter-spacing: 1.4px;
  color: #475569;
  text-transform: uppercase;
}
.card-viewer-placeholder .fw-langs {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: #7dd3fc;
  text-align: center;
  line-height: 2;
}

/* Compact card footer */
.card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 13px;
  border-top: 1px solid var(--border);
  gap: 8px;
}
.card-footer h3 {
  font-size: 0.88rem;
  font-weight: 600;
  line-height: 1.3;
}
.project-date { font-family: var(--font-mono); font-size: 0.82rem; color: var(--text-muted); }

/* ── PROJECT PAGES: back nav ── */
.back-nav {
  margin-bottom: 2rem;
  font-family: var(--font-mono);
  font-size: 0.8rem;
}
.back-nav a { color: var(--text-muted); }
.back-nav a:hover { color: var(--text-main); }

.project-page-header {
  margin-bottom: 2.2rem;
  border-left: 4px solid var(--text-main);
  padding-left: 20px;
}
.project-page-header h1 { font-size: 1.7rem; font-weight: 600; margin-bottom: 0.2rem; }

/* ── CAD Viewer (project pages) ── */
.cad-container {
  width: 100%;
  height: 500px;
  background-color: #fcfcfc;
  border: 1px solid var(--border);
  margin-top: 1.2rem;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.viewer-area { flex-grow: 1; position: relative; width: 100%; overflow: hidden; }

.cad-label {
  position: absolute;
  top: 12px; left: 12px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--text-muted);
  z-index: 10;
  letter-spacing: 1px;
  background: rgba(255,255,255,0.85);
  padding: 2px 6px;
  border: 1px solid var(--border);
  display: none;
}

model-viewer { width: 100%; height: 100%; outline: none; }

.schematic-img {
  position: absolute; top: 0; left: 0;
  width: 100%; height: 100%;
  object-fit: contain;
  background: #fcfcfc;
  z-index: 5;
  display: none;
  cursor: grab;
  transform-origin: center;
  transition: transform 0.1s ease;
}
.schematic-img.active { display: block; }
.schematic-img:active { cursor: grabbing; }

.view-controls {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  background: #f4f4f4;
  padding: 10px 12px;
  border-top: 1px solid var(--border);
  z-index: 20;
}

.view-btn {
  background: #ffffff;
  border: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  cursor: pointer;
  padding: 6px 12px;
  border-radius: 4px;
  transition: all 0.2s;
}
.view-btn.active { background: var(--text-main); color: #fff; border-color: var(--text-main); }

/* ── Code Snippet ── */
.code-snippet {
  margin-top: 1.2rem;
  border: 1px solid var(--border);
  background: #0f172a;
  color: #e5e7eb;
  border-radius: 6px;
  overflow: hidden;
  font-family: var(--font-mono);
}
.code-snippet-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #111827;
  color: #cbd5e1;
  padding: 8px 12px;
  font-size: 0.72rem;
  letter-spacing: 0.8px;
  text-transform: uppercase;
  border-bottom: 1px solid #1f2937;
}
.code-snippet pre {
  margin: 0; padding: 14px 16px;
  overflow-x: auto;
  font-size: 0.78rem;
  line-height: 1.55;
  white-space: pre;
}
.code-snippet code { font-family: var(--font-mono); }
.copy-btn {
  background: transparent;
  color: #cbd5e1;
  border: 1px solid #334155;
  border-radius: 4px;
  padding: 4px 8px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  cursor: pointer;
}
.copy-btn:hover { background: #1e293b; }

.code-panel {
  position: absolute; inset: 0;
  display: none; z-index: 6;
  background: #0f172a;
  color: #e5e7eb;
  overflow: hidden;
}
.code-panel.active { display: block; }
.code-panel .code-snippet { height: 100%; margin: 0; border: none; border-radius: 0; }
.code-panel .code-snippet pre { max-height: calc(100% - 42px); overflow: auto; }

/* ── Engineering Review ── */
.engineering-review { margin-top: 1.2rem; margin-bottom: 1.2rem; }

.review-section-title {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  letter-spacing: 1px;
  text-transform: uppercase;
  color: var(--text-main);
  margin: 1.2rem 0 0.6rem;
}

.review-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; }

.review-card {
  border: 1px solid var(--border);
  background: #fbfbfb;
  padding: 12px 14px;
  border-radius: 6px;
}
.review-card h4 { font-size: 0.9rem; font-weight: 600; margin-bottom: 0.45rem; }
.review-card ul { margin-left: 16px; color: var(--text-muted); font-size: 0.86rem; }
.review-card li { margin-bottom: 0.35rem; }

.decision-table {
  width: 100%;
  border-collapse: collapse;
  border: 1px solid var(--border);
  font-size: 0.86rem;
  margin-top: 0.6rem;
}
.decision-table th, .decision-table td {
  border-bottom: 1px solid var(--border);
  padding: 8px 10px;
  text-align: left;
  vertical-align: top;
}
.decision-table th {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.8px;
  text-transform: uppercase;
  background: #f4f4f4;
  color: var(--text-main);
}
.decision-table td:first-child { font-weight: 600; color: var(--text-main); white-space: nowrap; }

.verification-plan {
  border-left: 3px solid var(--text-main);
  background: #fbfbfb;
  padding: 12px 14px;
  margin-top: 0.6rem;
  color: var(--text-muted);
  font-size: 0.86rem;
}
.verification-plan ul { margin-left: 16px; }
.verification-plan li { margin-bottom: 0.35rem; }

/* ── Side Tabs (project pages) ── */
.anchor-target { scroll-margin-top: 28px; }

.side-tabs {
  position: fixed;
  top: 118px;
  left: max(14px, calc((100vw - 800px) / 2 - 195px));
  width: 170px;
  z-index: 50;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.7px;
  text-transform: uppercase;
}
.side-tabs-title { color: #999; font-size: 0.62rem; margin-bottom: 8px; padding-left: 12px; }
.side-tabs a {
  display: block;
  color: #777;
  border-left: 2px solid var(--border);
  padding: 5px 0 5px 10px;
  line-height: 1.25;
  text-decoration: none;
  transition: color 0.15s ease, border-color 0.15s ease, padding-left 0.15s ease;
}
.side-tabs a:hover { color: var(--text-main); border-left-color: #aaa; padding-left: 13px; text-decoration: none; }
.side-tabs a.active { color: var(--text-main); border-left-color: var(--text-main); padding-left: 13px; }

/* ── Responsive ── */
@media (max-width: 600px) {
  .cards-grid { grid-template-columns: 1fr; }
  .cad-container { height: 400px; }
  .side-tabs { display: none; }
  .review-grid { grid-template-columns: 1fr; }
  .decision-table td:first-child { white-space: normal; }
}
@media (max-width: 1200px) { .side-tabs { display: none; } }