/* Sergii Danyliuk — personal site. Editorial dark-first design.
   Theme: dark by default, light via prefers-color-scheme or the toggle
   (data-theme attribute set by a small first-party script). */

:root {
  --bg: #141517;
  --bg-raised: #1c1e21;
  --text: #e9eaec;
  --text-dim: #9ba0a6;
  --accent: #43c9b0;
  --accent-ink: #0e2d27;
  --line: #2c2f33;
  --line-strong: #4a4e54;
  --chip-bg: #22252a;
}

@media (prefers-color-scheme: light) {
  :root:not([data-theme="dark"]) {
    --bg: #f4f2ed;
    --bg-raised: #ebe8e1;
    --text: #1b1d1f;
    --text-dim: #5b6065;
    --accent: #0c7c68;
    --accent-ink: #eafaf6;
    --line: #d8d4cb;
    --line-strong: #b4afa4;
    --chip-bg: #e4e0d7;
  }
}
:root[data-theme="light"] {
  --bg: #f4f2ed;
  --bg-raised: #ebe8e1;
  --text: #1b1d1f;
  --text-dim: #5b6065;
  --accent: #0c7c68;
  --accent-ink: #eafaf6;
  --line: #d8d4cb;
  --line-strong: #b4afa4;
  --chip-bg: #e4e0d7;
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.65;
  font-size: 1rem;
}

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

/* ---------- Top bar ---------- */
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 0.8rem clamp(1rem, 4vw, 2.5rem);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.brand {
  color: var(--text);
  font-weight: 700;
  letter-spacing: -0.01em;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  white-space: nowrap;
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 0.7em;
  height: 0.7em;
  background: var(--accent);
  display: inline-block;
}
.topnav { display: flex; align-items: center; gap: clamp(0.7rem, 2vw, 1.4rem); }
.topnav a { color: var(--text-dim); font-size: 0.92rem; }
.topnav a:hover { color: var(--text); text-decoration: none; }
.btn-contact {
  background: var(--accent);
  color: var(--accent-ink) !important;
  padding: 0.35rem 0.95rem;
  font-weight: 600;
}
.btn-contact:hover { text-decoration: none; filter: brightness(1.08); }
.theme-toggle {
  background: none;
  border: 1px solid var(--line-strong);
  color: var(--text);
  font-size: 0.95rem;
  width: 1.9rem;
  height: 1.9rem;
  border-radius: 50%;
  cursor: pointer;
  line-height: 1;
}
.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }

/* ---------- Layout ---------- */
main { max-width: 66rem; margin: 0 auto; padding: 0 clamp(1rem, 4vw, 2.5rem); }
.section { padding: clamp(2.5rem, 6vw, 4.5rem) 0; border-top: 1px solid var(--line); }
.section h2 {
  font-size: clamp(1.6rem, 3.5vw, 2.2rem);
  letter-spacing: -0.02em;
  margin-bottom: 0.8rem;
}
.section-lede { color: var(--text-dim); max-width: 44rem; margin-bottom: 2.2rem; }

.eyebrow {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin-bottom: 1rem;
}

/* ---------- Hero ---------- */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: clamp(1.5rem, 5vw, 4rem);
  align-items: center;
  padding: clamp(2.5rem, 7vw, 5.5rem) 0;
}
.hero h1 {
  font-size: clamp(2.3rem, 5.6vw, 3.9rem);
  line-height: 1.06;
  letter-spacing: -0.03em;
  font-weight: 800;
  margin-bottom: 1.3rem;
}
.hero-sub { color: var(--text-dim); max-width: 34rem; margin-bottom: 1.6rem; }
.hero-cta { display: flex; align-items: center; gap: 1.3rem; flex-wrap: wrap; font-size: 0.95rem; }
.btn-primary {
  background: var(--accent);
  color: var(--accent-ink);
  padding: 0.55rem 1.2rem;
  font-weight: 700;
}
.btn-primary:hover { text-decoration: none; filter: brightness(1.08); }
.hero-photo { border-top: 1px solid var(--line-strong); padding-top: 1rem; }
.hero-photo img {
  width: 100%;
  height: auto;
  display: block;
  aspect-ratio: 4 / 5;
  object-fit: cover;
  object-position: 50% 18%;
}

/* ---------- Stats ---------- */
.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.stats div { background: var(--bg); padding: 1.4rem 1rem; text-align: left; }
.stats strong {
  display: block;
  font-size: clamp(1.5rem, 3vw, 2.1rem);
  letter-spacing: -0.02em;
  color: var(--text);
}
.stats span {
  color: var(--text-dim);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

/* ---------- Work ---------- */
.work {
  display: grid;
  grid-template-columns: 5rem minmax(0, 1fr);
  gap: 1rem;
  padding: 2.2rem 0;
  border-top: 1px solid var(--line);
}
.work:first-of-type { border-top: none; padding-top: 0.5rem; }
.work-index {
  font-size: 1.6rem;
  font-weight: 800;
  color: var(--accent);
  letter-spacing: -0.02em;
}
.work-body h3 {
  font-size: clamp(1.2rem, 2.4vw, 1.55rem);
  letter-spacing: -0.02em;
  margin-bottom: 0.35rem;
}
.work-meta {
  color: var(--text-dim);
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  margin-bottom: 1rem;
}
.work-body p { max-width: 44rem; margin-bottom: 0.9rem; }
.stack { list-style: none; display: flex; flex-wrap: wrap; gap: 0.45rem; margin-top: 1.1rem; }
.stack li {
  background: var(--chip-bg);
  border: 1px solid var(--line);
  color: var(--text-dim);
  font-size: 0.78rem;
  font-weight: 600;
  padding: 0.22rem 0.7rem;
}

/* ---------- About ---------- */
#about p { max-width: 46rem; margin-bottom: 1rem; }
#about .eyebrow { margin-bottom: 1.2rem; }

/* ---------- Experience ---------- */
.job { padding: 1.6rem 0; border-top: 1px solid var(--line); }
.job:first-of-type { border-top: none; padding-top: 0.5rem; }
.job-head { display: flex; align-items: baseline; gap: 1rem; flex-wrap: wrap; }
.job-head h3 { font-size: 1.3rem; letter-spacing: -0.02em; }
.job-loc {
  color: var(--text-dim);
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}
.job-role { font-weight: 600; margin: 0.4rem 0 0.9rem; }
.job-role span { color: var(--text-dim); font-weight: 400; margin-left: 0.6rem; }
.job ul { list-style: none; max-width: 48rem; }
.job li {
  position: relative;
  padding-left: 1.2rem;
  margin-bottom: 0.65rem;
  color: var(--text);
}
.job li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.68em;
  width: 0.42em;
  height: 0.42em;
  background: var(--accent);
}

/* ---------- Skills ---------- */
.skills div {
  display: grid;
  grid-template-columns: 14rem minmax(0, 1fr);
  gap: 1rem;
  padding: 0.7rem 0;
  border-top: 1px solid var(--line);
}
.skills div:first-of-type { border-top: none; }
.skills dt {
  color: var(--text-dim);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding-top: 0.2rem;
}
.skills dd { color: var(--text); }
.certs-title {
  margin-top: 2.2rem;
  margin-bottom: 0.8rem;
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-dim);
}
.certs { list-style: none; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.certs li {
  background: var(--chip-bg);
  border: 1px solid var(--line);
  padding: 0.3rem 0.85rem;
  font-size: 0.85rem;
}

/* ---------- Colophon ---------- */
.colophon div {
  display: grid;
  grid-template-columns: 8rem minmax(0, 1fr);
  gap: 1rem;
  padding: 0.5rem 0;
}
.colophon dt {
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  padding-top: 0.25rem;
}
.colophon dd { color: var(--text-dim); }

/* ---------- Footer ---------- */
footer {
  border-top: 1px solid var(--line);
  padding: 1.5rem clamp(1rem, 4vw, 2.5rem) 2.5rem;
  max-width: 66rem;
  margin: 0 auto;
  font-size: 0.9rem;
  color: var(--text-dim);
}

/* ---------- Responsive ---------- */
@media (max-width: 760px) {
  .topnav a:not(.btn-contact) { display: none; }
  .hero { grid-template-columns: 1fr; }
  .hero-photo { max-width: 20rem; }
  .stats { grid-template-columns: 1fr 1fr; }
  .work { grid-template-columns: 1fr; gap: 0.3rem; }
  .work-index { font-size: 1.2rem; }
  .skills div { grid-template-columns: 1fr; gap: 0.15rem; }
  .colophon div { grid-template-columns: 1fr; gap: 0.1rem; }
}