/* ==================================================================
   Concrete & Ink — Arnas Vaškevičius portfolio
   Vanilla CSS, no build. Monochrome (concrete + ink), one black spine.
================================================================== */

:root {
  /* concrete + light */
  --paper:        #ECEAE5;
  --concrete-100: #DEDBD5;
  --concrete-200: #D4D0C9;
  --concrete-300: #C2BEB6;
  --concrete-500: #8C8780;
  /* ink */
  --ink:          #141414;
  --ink-line:     #000000;
  --hairline:     rgba(20,20,20,.18);

  /* type */
  --font-display: "Space Grotesk", system-ui, sans-serif;
  --font-body:    "Inter", system-ui, sans-serif;
  --font-mono:    "JetBrains Mono", ui-monospace, monospace;

  /* scale */
  --step-hero: clamp(3rem, 9vw, 7rem);
  --step-h2:   clamp(1.9rem, 4.2vw, 3.2rem);
  --step-h3:   clamp(1.15rem, 1.8vw, 1.45rem);
  --step-body: clamp(1rem, 1.05vw, 1.125rem);
  --step-mono: .76rem;

  /* spacing */
  --pad-section: clamp(4.5rem, 11vh, 10rem);
  --gutter:      clamp(1.25rem, 4.5vw, 4.5rem);
  --spine-x:     clamp(18px, 6vw, 84px);
  --content-max: 1120px;
}

/* ---------- reset / base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--concrete-100);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--step-body);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
h1, h2, h3 { font-family: var(--font-display); font-weight: 700; line-height: 1.02; margin: 0; }
p { margin: 0; }
a { color: inherit; text-decoration: none; }
img, video { display: block; max-width: 100%; }
ul { margin: 0; padding: 0; list-style: none; }
.mono { font-family: var(--font-mono); font-size: var(--step-mono); letter-spacing: .04em; }

section { scroll-margin-top: 5rem; }

/* centered content column (sections stay full-width for backgrounds) */
.wrap { width: 100%; max-width: var(--content-max); margin-inline: auto; }

/* ---------- skip link ---------- */
.skip-link {
  position: absolute; left: -999px; top: 0; z-index: 100;
  background: var(--ink); color: var(--paper); padding: .6rem 1rem; font-family: var(--font-mono);
}
.skip-link:focus { left: 0; }

/* ---------- concrete grain ---------- */
.grain {
  position: fixed; inset: 0; z-index: 40; pointer-events: none; opacity: .045;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='180' height='180'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* ---------- spine (the black datum line) ---------- */
.spine {
  position: fixed; top: 0; bottom: 0; left: var(--spine-x); width: 1.5px;
  background: var(--hairline); z-index: 30; pointer-events: none;
}
.spine__progress { position: absolute; top: 0; left: 0; width: 100%; height: 0; background: var(--ink-line); }

/* ---------- nav ---------- */
.nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between;
  padding: .85rem var(--gutter) .85rem calc(var(--spine-x) + .55rem);
  transition: background .3s ease, border-color .3s ease;
  border-bottom: 1px solid transparent;
}
.nav--scrolled { background: color-mix(in srgb, var(--paper) 88%, transparent); backdrop-filter: blur(8px); border-bottom-color: var(--hairline); }
.nav__mark { font-family: var(--font-display); font-weight: 700; font-size: 1.15rem; letter-spacing: -.01em; }
.nav__dot { color: var(--concrete-500); }
.nav__menu ul { display: flex; gap: clamp(1rem, 2.2vw, 2.2rem); }
.nav__menu a { font-family: var(--font-mono); font-size: var(--step-mono); letter-spacing: .04em; padding-bottom: 2px; border-bottom: 1px solid transparent; transition: border-color .2s ease; }
.nav__menu a:hover, .nav__menu a:focus-visible { border-bottom-color: var(--ink); }
.nav__menu .mono { color: var(--concrete-500); margin-right: .3em; }
.nav__toggle { display: none; }

/* ---------- hero ---------- */
.hero {
  min-height: 100svh; display: flex; flex-direction: column; justify-content: center;
  padding: 7rem var(--gutter) 4rem;
  background: radial-gradient(120% 90% at 60% 0%, var(--paper) 0%, var(--concrete-100) 55%);
  position: relative;
}
.hero__eyebrow { color: var(--concrete-500); margin-bottom: 1.6rem; }
.hero__title { font-size: var(--step-hero); letter-spacing: -.02em; }
.hero__title--sm { font-size: clamp(2.5rem, 7vw, 5rem); }
.hero__lede { max-width: 46ch; margin-top: 1.8rem; font-size: clamp(1.05rem, 1.5vw, 1.35rem); color: #2a2a2a; }
.hero__cue { display: inline-block; margin-top: 3rem; color: var(--concrete-500); }
@media (prefers-reduced-motion: no-preference) {
  .hero__cue { animation: nudge 1.8s ease-in-out infinite; }
  @keyframes nudge { 0%,100%{ transform: translateY(0); opacity:.7 } 50%{ transform: translateY(5px); opacity:1 } }
}

/* ---------- sections ---------- */
.section { padding: var(--pad-section) var(--gutter); }
.section--alt { background: var(--concrete-200); }
.section__head { max-width: 60ch; margin-bottom: clamp(2.5rem, 5vw, 4rem); }
.section__head--sub { margin-top: clamp(3rem, 6vw, 5rem); }
.section__index { display: inline-block; color: var(--concrete-500); margin-bottom: 1rem; }
.section__title { font-size: var(--step-h2); letter-spacing: -.015em; }
.section__title--sm { font-size: var(--step-h3); }
.section__lede { margin-top: 1rem; color: #333; max-width: 56ch; }

/* ---------- grid + cards ---------- */
.grid { display: flex; flex-direction: column; gap: clamp(3rem, 7vw, 6rem); }
.card { display: grid; grid-template-columns: 1.15fr 1fr; gap: var(--gutter); align-items: center; }

.card__panel {
  position: relative; aspect-ratio: 16 / 10; background: var(--concrete-300);
  overflow: hidden; border: 1px solid var(--hairline);
}
.card__panel > * { position: absolute; inset: 0; }
.card__pic { display: block; }
.card__media { width: 100%; height: 100%; object-fit: contain; }
.card__media--over { background: var(--concrete-300); }

/* split panel: physical photo | CAD movie, divided by a hairline.
   Lock the row to the panel height so a portrait photo's aspect ratio
   can't stretch the row and clip/offset the contents. */
.card__split { display: grid; grid-template-columns: 1fr 1fr; grid-template-rows: 100%; gap: 1px; background: var(--hairline); }
.card__split > .card__pic,
.card__split > video { width: 100%; height: 100%; min-width: 0; min-height: 0; background: var(--concrete-300); }

/* blueprint placeholder */
.blueprint {
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: .5rem;
  text-align: center; padding: 1rem; box-shadow: inset 0 0 0 1px var(--hairline);
  background:
    linear-gradient(var(--hairline) 1px, transparent 1px) 0 0 / 100% 28px,
    var(--concrete-300);
}
.blueprint__idx { font-size: clamp(1.6rem, 3vw, 2.4rem); color: var(--ink); }
.blueprint__label { letter-spacing: .18em; color: var(--ink); }
.blueprint__note { font-size: .6rem; letter-spacing: .22em; color: var(--concrete-500); text-transform: uppercase; }

.card__index { display: block; color: var(--concrete-500); margin-bottom: .7rem; }
.card__title { font-size: var(--step-h3); margin-bottom: .8rem; }
.card__blurb { color: #2c2c2c; max-width: 46ch; }
.card__stack { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1.2rem; }
.chip {
  font-family: var(--font-mono); font-size: .68rem; letter-spacing: .03em;
  padding: .32rem .6rem; border: 1px solid var(--hairline); color: #333;
}
.card__credit { margin-top: 1.2rem; color: var(--concrete-500); font-size: .68rem; line-height: 1.5; max-width: 46ch; }

/* ---------- about / background / contact ---------- */
.prose { max-width: 62ch; }
.prose p { margin-bottom: 1.2rem; }
.prose strong { font-weight: 500; }

.facts__list { max-width: 70ch; border-top: 1px solid var(--hairline); }
.facts__row { display: grid; grid-template-columns: 90px 1fr; gap: 1.5rem; padding: 1.3rem 0; border-bottom: 1px solid var(--hairline); }
.facts__row dt { color: var(--concrete-500); letter-spacing: .12em; padding-top: .15rem; }
.facts__row dd { margin: 0; }
.chips { display: flex; flex-wrap: wrap; gap: .5rem; }

.contact { display: flex; flex-direction: column; gap: 1.1rem; }
.contact__link { font-size: clamp(1.1rem, 2vw, 1.5rem); font-family: var(--font-display); width: fit-content; border-bottom: 1px solid var(--hairline); padding-bottom: .25rem; transition: border-color .2s ease; }
.contact__link:hover, .contact__link:focus-visible { border-bottom-color: var(--ink); }
.contact__link .mono { color: var(--concrete-500); margin-right: .6em; font-family: var(--font-mono); }
.contact__loc { color: #333; }
.contact__loc .mono { color: var(--concrete-500); margin-right: .6em; }

/* ---------- footer ---------- */
.footer { padding: 3rem var(--gutter); border-top: 1px solid var(--hairline); }
.footer__credits { max-width: 90ch; color: var(--concrete-500); font-size: .64rem; line-height: 1.7; }
.footer__copy { margin-top: 1rem; color: var(--concrete-500); font-size: .64rem; }

/* ---------- reveal motion ---------- */
[data-reveal] { opacity: 0; transform: translateY(24px); transition: opacity .6s ease, transform .6s ease; }
[data-reveal].in { opacity: 1; transform: none; }

/* ---------- responsive ---------- */
@media (max-width: 860px) {
  .nav__toggle {
    display: flex; flex-direction: column; justify-content: center; gap: 5px;
    width: 40px; height: 40px; background: none; border: none; cursor: pointer; z-index: 60;
  }
  .nav__toggle span { display: block; height: 1.6px; width: 22px; background: var(--ink); transition: transform .25s ease, opacity .25s ease; }
  body.nav-open .nav__toggle span:nth-child(1) { transform: translateY(3.3px) rotate(45deg); }
  body.nav-open .nav__toggle span:nth-child(2) { transform: translateY(-3.3px) rotate(-45deg); }

  .nav__menu {
    position: fixed; inset: 0; background: var(--paper);
    display: flex; align-items: center; justify-content: center;
    opacity: 0; visibility: hidden; transition: opacity .3s ease, visibility .3s ease;
  }
  body.nav-open .nav__menu { opacity: 1; visibility: visible; }
  .nav__menu ul { flex-direction: column; gap: 1.6rem; text-align: left; }
  .nav__menu a { font-size: 1.1rem; }

  .card { grid-template-columns: 1fr; gap: 1.5rem; }
  .facts__row { grid-template-columns: 1fr; gap: .4rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  [data-reveal] { opacity: 1; transform: none; transition: none; }
  .hero__cue { animation: none; }
}