/* =================================================================
   bds421 — physics.bds421.com
   "Applied AI for the Unification of Physics"
   Light house shell. Tokens + fonts come from ../shared/tokens.css.
   Self-contained on purpose: this file must resolve identically at
   bds421.com/physics/ (path) and physics.bds421.com/ (subdomain),
   so it does NOT depend on the main site's website/styles.css.
   ================================================================= */

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--fg-1);
}

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 32px;
}

/* ---- Nav ------------------------------------------------------- */
.nav {
  position: sticky;
  top: 0;
  background: rgba(245, 246, 248, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: var(--bw-1) solid var(--line);
  z-index: 110;
}
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--nav-h);
}
.brand {
  display: flex;
  align-items: baseline;
  gap: 0;
  font-family: 'JetBrains Mono', 'IBM Plex Mono', 'SFMono-Regular', Menlo, monospace;
  font-weight: 700;
  font-size: 22px;
  letter-spacing: -0.04em;
  text-decoration: none;
  color: var(--fg-1);
  background-image: none;
}
.brand:hover { text-decoration: none; background-image: none; }
.brand .n { color: var(--accent); }
.brand .sep {
  font-family: var(--font-mono);
  font-weight: var(--fw-medium);
  font-size: 14px;
  color: var(--fg-4);
  margin: 0 8px;
}
.brand .tag {
  font-family: var(--font-mono);
  font-weight: var(--fw-medium);
  font-size: 14px;
  color: var(--fg-2);
  display: inline-block;
  min-width: 9ch;
  text-transform: lowercase;
}
#brand-tag::after {
  content: "█";
  margin-left: 1px;
  color: var(--accent);
  animation: tagblink 1.1s steps(1) infinite;
  font-weight: var(--fw-regular);
}
@keyframes tagblink {
  0%, 50%   { opacity: 1; }
  51%, 100% { opacity: 0; }
}

.nav-links {
  display: flex;
  gap: 32px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-links a {
  font-family: var(--font-sans);
  font-size: 14px;
  color: var(--fg-2);
}
.nav-right {
  display: flex;
  align-items: center;
  gap: 20px;
}
/* Link back to the main site — pill, styled like the homepage lang toggle */
.home-link {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.04em;
  color: var(--fg-3);
  border: var(--bw-1) solid var(--line);
  border-radius: var(--r-pill);
  padding: 5px 12px;
  text-decoration: none;
  background-image: none;
  transition: color var(--dur-micro) var(--ease), border-color var(--dur-micro) var(--ease);
}
.home-link:hover { color: var(--ink); border-color: var(--line-strong); background-image: none; }

/* ---- Mobile menu ----------------------------------------------- */
.nav-toggle {
  display: none;
  width: 36px; height: 36px;
  background: transparent; border: 0; padding: 0;
  cursor: pointer;
  flex-direction: column; justify-content: center; align-items: center; gap: 5px;
}
.nav-toggle span {
  display: block; width: 22px; height: 2px;
  background: var(--ink);
  transform-origin: center;
  transition: transform 220ms var(--ease), opacity 150ms var(--ease);
}
body.menu-open .nav-toggle span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
body.menu-open .nav-toggle span:nth-child(2) { opacity: 0; }
body.menu-open .nav-toggle span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

.mobile-menu { position: fixed; inset: 0; z-index: 100; pointer-events: none; }
.mobile-menu-backdrop {
  position: absolute; inset: 0;
  background: rgba(10, 10, 10, 0.45);
  opacity: 0; pointer-events: none;
  transition: opacity 280ms var(--ease);
}
.mobile-menu-inner {
  position: absolute; top: 0; right: 0; bottom: 0;
  width: min(420px, 100vw);
  background: var(--ink); color: var(--paper);
  padding: 96px 32px 32px;
  display: flex; flex-direction: column; overflow-y: auto;
  transform: translateX(100%);
  transition: transform 280ms var(--ease);
  pointer-events: auto;
}
body.menu-open .mobile-menu { pointer-events: auto; }
body.menu-open .mobile-menu-backdrop { opacity: 1; pointer-events: auto; }
body.menu-open .mobile-menu-inner { transform: translateX(0); }
body.menu-open { overflow: hidden; }
.mobile-menu ul {
  list-style: none; padding: 0; margin: 0 0 auto;
  display: flex; flex-direction: column; gap: 4px;
}
.mobile-menu a {
  color: var(--paper);
  font-family: var(--font-display);
  font-size: 32px; font-weight: var(--fw-semi);
  letter-spacing: -0.02em; text-decoration: none;
  padding: 10px 0; display: block; background-image: none;
  transition: color var(--dur-micro) var(--ease);
}
.mobile-menu a:hover { color: var(--accent); text-decoration: none; }
.mobile-menu-foot {
  padding-top: 32px;
  border-top: var(--bw-1) solid #24272B;
  display: flex; flex-direction: column; gap: 20px; align-items: flex-start;
}
.mobile-menu-meta {
  font-family: var(--font-mono);
  font-size: 11px; color: var(--fg-5); letter-spacing: 0.08em;
}

/* ---- Buttons --------------------------------------------------- */
.btn {
  font-family: var(--font-sans);
  font-weight: var(--fw-medium);
  font-size: 14px;
  padding: 9px 16px;
  border-radius: var(--r-1);
  border: var(--bw-1) solid transparent;
  cursor: pointer; text-decoration: none;
  display: inline-flex; align-items: center; gap: 10px; line-height: 1;
  position: relative; background-image: none;
  transition: background 140ms var(--ease), border-color 140ms var(--ease),
              color 140ms var(--ease), box-shadow 140ms var(--ease),
              transform 140ms var(--ease);
}
.btn, .btn:hover { text-decoration: none; background-image: none; }
.btn:active { transform: translateY(1px); }
.btn.primary {
  background: var(--ink); color: var(--paper);
  border-color: var(--ink); box-shadow: 3px 3px 0 var(--accent);
}
.btn.primary:hover {
  background: var(--accent); border-color: var(--accent);
  box-shadow: 0 0 0 var(--accent); transform: translate(3px, 3px); color: var(--paper);
}
.btn.primary:active { transform: translate(3px, 4px); }
.btn.secondary {
  background: transparent; color: var(--fg-1);
  border-color: var(--line-strong);
  font-family: var(--font-mono); font-size: 12px; font-weight: var(--fw-medium);
}
.btn.secondary:hover {
  border-color: var(--ink); background: var(--paper);
  box-shadow: inset 0 -2px 0 var(--accent);
}
.btn:focus-visible { outline: var(--bw-2) solid var(--accent); outline-offset: 2px; }

/* ---- Hero ------------------------------------------------------ */
.hero {
  padding: 96px 0 64px;
  border-bottom: var(--bw-1) solid var(--line);
}
.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--fs-xs);
  font-weight: var(--fw-bold);
  color: var(--fg-3);
  letter-spacing: var(--tr-eyebrow);
  text-transform: uppercase;
  margin-bottom: 24px;
}
.hero h1 {
  font-size: clamp(28px, 7vw, 80px);
  line-height: 0.98;
  letter-spacing: -0.03em;
  font-weight: var(--fw-bold);
  margin: 0 0 24px;
  max-width: 16ch;
  overflow-wrap: break-word;
}
.hero h1 .n { color: var(--accent); }
.hero p {
  font-size: 20px; color: var(--fg-2);
  max-width: 60ch; line-height: 1.4; margin: 0 0 40px;
}
.hero-cta { display: flex; gap: 12px; flex-wrap: wrap; }
.hero-meta {
  display: flex; gap: 0;
  margin-top: 64px; padding-top: 32px;
  border-top: var(--bw-1) solid var(--line);
  font-family: var(--font-mono); font-size: var(--fs-xs);
  color: var(--fg-3); letter-spacing: 0.04em; flex-wrap: wrap;
}
.hero-meta span + span::before { content: " · "; color: var(--fg-4); white-space: pre; }

/* ---- Sections -------------------------------------------------- */
.section { padding: 96px 0; border-bottom: var(--bw-1) solid var(--line); }
.section.alt { background: var(--paper-soft); }
.section h2 {
  font-size: 48px; line-height: 1.05; letter-spacing: -0.02em;
  font-weight: var(--fw-semi); margin: 0 0 16px; max-width: 22ch;
}
.section .lede {
  font-size: 18px; color: var(--fg-2); max-width: 64ch; margin: 0 0 56px;
}
.section .lede strong { color: var(--fg-1); font-weight: var(--fw-semi); }

/* ---- Idea grid ------------------------------------------------- */
.idea-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  border: var(--bw-1) solid var(--ink);
  border-top: var(--bw-2) solid var(--accent);
  background: var(--paper);
}
.idea-cell {
  padding: 24px 22px 22px;
  border-right: var(--bw-1) solid var(--line);
  display: flex; flex-direction: column; gap: 8px;
}
.idea-cell:last-child { border-right: 0; }
.idea-cell .i-sym {
  font-family: var(--font-mono);
  font-size: 11px; font-weight: var(--fw-bold);
  color: var(--accent); letter-spacing: 0.14em; text-transform: uppercase;
}
.idea-cell h3 {
  font-family: var(--font-display);
  font-size: 18px; font-weight: var(--fw-semi);
  letter-spacing: -0.01em; line-height: 1.2; margin: 0;
}
.idea-cell p { font-size: 13px; color: var(--fg-2); line-height: 1.55; margin: 0; }
.idea-cell .mono { font-family: var(--font-mono); color: var(--accent-2); font-size: 12px; }

/* ---- Chat mock ("Ask the graph") ------------------------------- */
.chat {
  border: var(--bw-1) solid var(--ink);
  background: var(--paper);
  max-width: 760px;
}
.chat-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 18px;
  background: var(--ink); color: var(--paper);
}
.chat-title {
  font-family: var(--font-mono); font-size: 13px;
  font-weight: var(--fw-medium); letter-spacing: 0.02em;
}
.chat-title::before { content: "▌ "; color: var(--accent); }
.chat-status {
  font-family: var(--font-mono); font-size: 10px;
  letter-spacing: 0.14em; text-transform: uppercase;
  color: var(--fg-5);
  border: var(--bw-1) solid #3A3F45; border-radius: var(--r-pill);
  padding: 3px 9px;
}
.chat-log {
  padding: 20px 18px;
  display: flex; flex-direction: column; gap: 16px;
  min-height: 120px;
}
.msg { display: flex; flex-direction: column; gap: 6px; max-width: 92%; }
.msg.user { align-self: flex-end; align-items: flex-end; }
.msg.bot  { align-self: flex-start; }
.msg-role {
  font-family: var(--font-mono); font-size: 10px;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--fg-3);
}
.msg-body {
  font-size: 14px; line-height: 1.55; color: var(--fg-1);
  padding: 12px 14px; border-radius: var(--r-2);
}
.msg.user .msg-body { background: var(--accent-soft); border: var(--bw-1) solid var(--accent); }
.msg.bot .msg-body  { background: var(--paper-soft); border: var(--bw-1) solid var(--line); }
.msg-body ol, .msg-body ul { margin: 6px 0 0; padding-left: 18px; }
.msg-body li { margin: 3px 0; }
.provenance {
  display: flex; flex-wrap: wrap; gap: 8px 14px;
  margin-top: 4px; align-self: flex-start;
  font-family: var(--font-mono); font-size: 11px; color: var(--fg-3);
}
.provenance .src::before { content: "source: "; color: var(--fg-4); }
.provenance .derived {
  color: var(--accent-2);
  border: var(--bw-1) dashed var(--accent-2);
  padding: 1px 7px; border-radius: var(--r-pill);
}
.typing { display: inline-flex; gap: 4px; padding: 12px 14px; }
.typing span {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--fg-4);
  animation: blink 1.2s infinite both;
}
.typing span:nth-child(2) { animation-delay: 0.2s; }
.typing span:nth-child(3) { animation-delay: 0.4s; }
@keyframes blink { 0%, 80%, 100% { opacity: 0.25; } 40% { opacity: 1; } }

.chat-suggest {
  display: flex; flex-wrap: wrap; gap: 8px;
  padding: 0 18px 16px;
}
.chip {
  font-family: var(--font-mono); font-size: 12px;
  color: var(--accent-ink);
  background: var(--paper-sunk);
  border: var(--bw-1) solid var(--line-strong);
  border-radius: var(--r-pill);
  padding: 7px 13px; cursor: pointer; line-height: 1.3;
  transition: background var(--dur-micro) var(--ease), border-color var(--dur-micro) var(--ease), color var(--dur-micro) var(--ease);
}
.chip:hover { background: var(--accent-soft); border-color: var(--accent); color: var(--accent-ink); }
.chip:focus-visible { outline: var(--bw-2) solid var(--accent); outline-offset: 2px; }
.chip[disabled] { opacity: 0.45; cursor: default; }

.chat-input {
  display: flex; gap: 0;
  border-top: var(--bw-1) solid var(--line);
}
.chat-input input {
  flex: 1; border: 0; background: transparent;
  padding: 14px 18px; font-family: var(--font-sans); font-size: 14px;
  color: var(--fg-1);
}
.chat-input input::placeholder { color: var(--fg-4); }
.chat-input input:disabled { cursor: not-allowed; }
.chat-input .send {
  border: 0; border-left: var(--bw-1) solid var(--line);
  background: transparent; color: var(--fg-4);
  font-family: var(--font-mono); font-size: 12px; letter-spacing: 0.08em;
  text-transform: uppercase; padding: 0 20px; cursor: not-allowed;
}
.chat-note {
  font-size: 13px; color: var(--fg-3); line-height: 1.55;
  margin: 18px 0 0; max-width: 64ch;
}
.chat-note strong { color: var(--fg-2); font-weight: var(--fw-medium); }

/* ---- Examples archive ------------------------------------------ */
.archive {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 24px;
}
.ex-card {
  display: flex; flex-direction: column;
  border: var(--bw-1) solid var(--ink);
  background: var(--paper);
  text-decoration: none; background-image: none;
  color: var(--fg-1);
  overflow: hidden;
  transition: box-shadow 160ms var(--ease), transform 160ms var(--ease);
}
a.ex-card:hover { text-decoration: none; background-image: none; box-shadow: var(--shadow-card); transform: translateY(-2px); }
.ex-thumb {
  height: 132px; position: relative; overflow: hidden;
  background:
    radial-gradient(ellipse 80% 70% at 50% 0%, rgba(92,242,160,0.10), transparent 60%),
    linear-gradient(180deg, #070d12, #04080b);
  border-bottom: var(--bw-1) solid var(--ink);
}
.ex-thumb::before {
  /* phosphor baseline + two "photon" dots, echoing the demo */
  content: "";
  position: absolute; left: 8%; right: 8%; top: 58%;
  border-top: 1px dashed rgba(92,242,160,0.35);
}
.ex-thumb::after {
  content: "";
  position: absolute; top: calc(58% - 4px); left: 70%;
  width: 7px; height: 7px; border-radius: 50%;
  background: #5cf2a0; box-shadow: -120px 9px 0 #ffb13b, 0 0 12px #5cf2a0;
}
.ex-scopelabel {
  position: absolute; top: 10px; left: 12px;
  font-family: var(--font-mono); font-size: 10px; letter-spacing: 0.2em;
  text-transform: uppercase; color: #2f7d57;
}
.ex-body { padding: 22px 24px 24px; display: flex; flex-direction: column; flex: 1; }
.ex-meta {
  display: flex; justify-content: space-between; align-items: baseline;
  font-family: var(--font-mono); font-size: 11px;
  letter-spacing: 0.1em; text-transform: uppercase; margin-bottom: 12px;
}
.ex-date { color: var(--accent); font-weight: var(--fw-bold); }
.ex-tag { color: var(--fg-4); }
.ex-card h3 {
  font-family: var(--font-display);
  font-size: 22px; font-weight: var(--fw-semi);
  letter-spacing: -0.015em; line-height: 1.18; margin: 0 0 10px;
}
.ex-card p { font-size: 14px; color: var(--fg-2); line-height: 1.55; margin: 0 0 18px; }
.ex-foot {
  display: flex; justify-content: space-between; align-items: center;
  margin-top: auto; padding-top: 14px;
  border-top: var(--bw-1) dashed var(--line);
  font-family: var(--font-mono); font-size: 11px; color: var(--fg-3); letter-spacing: 0.04em;
}
.ex-go { color: var(--accent); font-weight: var(--fw-bold); }
.ex-card.ex-next {
  border-style: dashed; border-color: var(--line-strong); background: transparent;
}
.ex-card.ex-next .ex-thumb {
  background: var(--paper-soft); border-bottom: var(--bw-1) dashed var(--line-strong);
}
.ex-card.ex-next .ex-thumb::before,
.ex-card.ex-next .ex-thumb::after { content: none; }
.ex-card.ex-next h3 { color: var(--fg-3); }
.ex-next-mark {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-size: 12px; letter-spacing: 0.2em;
  text-transform: uppercase; color: var(--fg-4);
}

/* ---- Experiment page (light chrome around a dark demo) --------- */
.exp-head { padding: 56px 0 36px; border-bottom: var(--bw-1) solid var(--line); }
.exp-head .eyebrow { margin-bottom: 16px; }
.exp-title {
  font-family: var(--font-display);
  font-size: 44px; line-height: 1.04; letter-spacing: -0.025em;
  font-weight: var(--fw-bold); color: var(--fg-1); margin: 0 0 16px; max-width: 20ch;
}
.exp-title .n { color: var(--accent); }
.exp-intro { font-size: 17px; color: var(--fg-2); line-height: 1.5; max-width: 64ch; margin: 0; }
.exp-cta {
  background: var(--paper-soft);
  border-bottom: var(--bw-1) solid var(--line);
  padding: 48px 0;
}
.exp-cta .container {
  display: flex; align-items: center; justify-content: space-between;
  gap: 24px; flex-wrap: wrap;
}
.exp-cta p { font-size: 18px; color: var(--fg-1); max-width: 52ch; margin: 0; }
@media (max-width: 640px) {
  .exp-title { font-size: 32px; }
  .exp-head { padding: 40px 0 28px; }
}

/* ---- Footer ---------------------------------------------------- */
.footer { background: var(--ink); color: var(--fg-5); padding: 64px 0 48px; }
.foot-grid {
  display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 48px; margin-bottom: 48px;
}
.foot-brand .brand { color: var(--paper); }
.foot-brand .brand .sep, .foot-brand .brand .tag { color: var(--fg-5); }
.foot-brand p { font-size: 13px; color: var(--fg-5); margin: 16px 0 0; line-height: 1.55; max-width: 36ch; }
.foot-col h3 {
  font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--paper); margin: 0 0 16px; font-weight: var(--fw-bold);
}
.foot-col ul { list-style: none; padding: 0; margin: 0; display: flex; flex-direction: column; gap: 8px; }
.foot-col a { color: var(--paper); font-size: 14px; text-decoration: none; background-image: none; transition: color var(--dur-micro) var(--ease); }
.foot-col a:hover { color: var(--accent); background-image: none; }
.foot-rule {
  border-top: var(--bw-1) solid #24272B; padding-top: 24px;
  display: flex; justify-content: space-between;
  font-family: var(--font-mono); font-size: 11px; color: var(--fg-5);
  letter-spacing: 0.04em; flex-wrap: wrap; gap: 16px;
}

/* ---- Responsive ------------------------------------------------ */
@media (max-width: 960px) {
  .nav-links { display: none; }
  .nav-toggle { display: inline-flex; }
  .nav-right > .home-link { display: none; }
  .section h2 { font-size: 36px; }
  .idea-grid { grid-template-columns: repeat(2, 1fr); }
  .idea-cell:nth-child(2n) { border-right: 0; }
  .idea-cell:nth-child(-n+2) { border-bottom: var(--bw-1) solid var(--line); }
  .foot-grid { grid-template-columns: 1fr 1fr; gap: 32px; }
}
@media (max-width: 640px) {
  .container { padding: 0 20px; }
  .hero { padding: 56px 0 40px; }
  .section { padding: 64px 0; }
  .idea-grid { grid-template-columns: 1fr; }
  .idea-cell { border-right: 0; border-bottom: var(--bw-1) solid var(--line); }
  .idea-cell:last-child { border-bottom: 0; }
  .archive { grid-template-columns: 1fr; }
  .foot-grid { grid-template-columns: 1fr; gap: 32px; }
}

/* ---- Motion preference ----------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
  #brand-tag::after { animation: none; opacity: 1; }
}