:root {
  --c-primary: #6366f1;
  --c-primary-dark: #4f46e5;
  --c-primary-soft: #eef2ff;
  --c-accent: #ec4899;
  --c-text: #0f172a;
  --c-text-2: #475569;
  --c-muted: #94a3b8;
  --c-surface: #ffffff;
  --c-bg: #f8fafc;
  --c-border: #e2e8f0;
  --c-border-2: #cbd5e1;
  --radius: 12px;
  --radius-lg: 18px;
  --shadow-sm: 0 1px 2px rgba(15,23,42,.05);
  --shadow: 0 4px 16px rgba(15,23,42,.06);
  --shadow-lg: 0 20px 40px -12px rgba(15,23,42,.15);
  --gradient: linear-gradient(135deg, #6366f1 0%, #8b5cf6 60%, #ec4899 100%);
  --gradient-soft: linear-gradient(180deg, #f1f5ff 0%, #f8fafc 100%);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  color: var(--c-text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI Variable", "Segoe UI",
               Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--c-bg);
  min-height: 100vh;
  display: flex; flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "cv02", "cv03", "cv11";
}

/* -------- Header -------- */
.site-header {
  display: flex; justify-content: space-between; align-items: center;
  padding: .9rem 2rem;
  background: rgba(255,255,255,.82);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--c-border);
  position: sticky; top: 0; z-index: 20;
}
.brand {
  display: flex; align-items: center; gap: .75rem;
  text-decoration: none; color: inherit;
  font-size: 1.15rem; font-weight: 700;
  letter-spacing: -.01em;
}
.brand::before {
  content: ''; width: 32px; height: 32px;
  background: var(--gradient); border-radius: 9px;
  box-shadow: 0 4px 14px rgba(99,102,241,.4), inset 0 1px 0 rgba(255,255,255,.2);
}
.brand-tag {
  font-size: .68rem; letter-spacing: .04em;
  background: var(--c-primary-soft); color: var(--c-primary-dark);
  padding: .22rem .6rem; border-radius: 999px;
  font-weight: 600; text-transform: uppercase;
}

.nav-right { display: flex; gap: .4rem; align-items: center; }
.nav-link {
  text-decoration: none; color: var(--c-text);
  font-size: .9rem; font-weight: 500;
  padding: .55rem .95rem; border-radius: 10px;
  transition: background .15s, color .15s;
}
.nav-link:hover { background: var(--c-primary-soft); color: var(--c-primary-dark); }
.nav-link.nav-btn {
  background: var(--gradient); color: #fff;
  box-shadow: 0 6px 16px rgba(99,102,241,.32), inset 0 1px 0 rgba(255,255,255,.15);
}
.nav-link.nav-btn:hover {
  background: var(--gradient);
  box-shadow: 0 8px 22px rgba(99,102,241,.45);
  transform: translateY(-1px);
  color: #fff;
}

/* -------- Hero -------- */
.hero {
  position: relative;
  max-width: 1600px; margin: 4.5rem auto 2.75rem;
  padding: 0 1.5rem; text-align: center;
}
.hero::before {
  content: ''; position: absolute; inset: -60px -40px auto auto;
  width: 320px; height: 320px; z-index: -1;
  background: radial-gradient(closest-side, rgba(236,72,153,.18), transparent 70%);
  filter: blur(20px); pointer-events: none;
}
.hero::after {
  content: ''; position: absolute; inset: -40px auto auto -40px;
  width: 320px; height: 320px; z-index: -1;
  background: radial-gradient(closest-side, rgba(99,102,241,.22), transparent 70%);
  filter: blur(20px); pointer-events: none;
}
.hero h1 {
  margin: 0 0 1rem;
  font-size: clamp(2rem, 5.5vw, 4.25rem);
  font-weight: 800; line-height: 1.08;
  letter-spacing: -.025em;
}
.hero p { max-width: 720px; }
.hero .accent {
  background: var(--gradient);
  -webkit-background-clip: text; background-clip: text;
  color: transparent;
}
.hero p {
  margin: 0 auto;
  color: var(--c-text-2);
  font-size: 1.1rem; line-height: 1.6;
  max-width: 620px;
}

/* -------- Category bar -------- */
.cat-bar {
  max-width: 1600px; margin: 0 auto 2rem;
  padding: 0 1.5rem;
  display: flex; gap: .5rem; flex-wrap: wrap; justify-content: center;
}
.cat-btn {
  padding: .7rem 1.2rem;
  background: var(--c-surface); border: 1px solid var(--c-border);
  color: var(--c-text);
  font-size: .9rem; font-weight: 600;
  border-radius: 999px;
  cursor: pointer;
  transition: all .2s cubic-bezier(.4,0,.2,1);
  box-shadow: var(--shadow-sm);
  display: inline-flex; align-items: center; gap: .5rem;
}
.cat-btn:hover {
  border-color: var(--c-primary);
  color: var(--c-primary-dark);
  transform: translateY(-2px);
  box-shadow: 0 6px 16px rgba(99,102,241,.14);
}
.cat-btn.active {
  background: var(--gradient); border-color: transparent;
  color: #fff;
  box-shadow: 0 8px 22px rgba(99,102,241,.38);
}
.cat-btn .count {
  font-size: .72rem; font-weight: 600;
  padding: .1rem .45rem; border-radius: 999px;
  background: var(--c-primary-soft); color: var(--c-primary-dark);
}
.cat-btn.active .count { background: rgba(255,255,255,.22); color: #fff; }

/* -------- Tests grid -------- */
.page {
  max-width: 1600px; margin: 0 auto; padding: 0 1.5rem 4rem;
  flex: 1 0 auto; width: 100%;
}
.tests-grid {
  display: grid; gap: 1.25rem;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
}
.test-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-lg);
  padding: 1.4rem 1.5rem 1.25rem;
  display: flex; flex-direction: column; gap: .65rem;
  position: relative; overflow: hidden;
  transition: transform .2s cubic-bezier(.4,0,.2,1), box-shadow .2s, border-color .2s;
}
.test-card::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: var(--gradient); opacity: 0; transition: opacity .2s;
}
.test-card:hover::before { opacity: 1; }
.test-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
}
.test-card .cat-pill {
  display: inline-flex; align-self: flex-start;
  font-size: .68rem; letter-spacing: .03em;
  background: var(--c-primary-soft); color: var(--c-primary-dark);
  padding: .22rem .65rem; border-radius: 999px;
  font-weight: 700; text-transform: uppercase;
}
.test-card h3 {
  margin: 0; font-size: 1.1rem; font-weight: 700;
  color: var(--c-text); letter-spacing: -.01em; line-height: 1.3;
}
.test-card .desc {
  margin: 0; color: var(--c-text-2);
  font-size: .88rem; line-height: 1.5;
  min-height: 1.2em;
}
.test-card .meta {
  display: flex; gap: 1rem; flex-wrap: wrap;
  color: var(--c-text-2); font-size: .82rem;
  margin-top: .35rem; padding-top: .75rem;
  border-top: 1px dashed var(--c-border);
}
.test-card .meta span {
  display: inline-flex; align-items: center; gap: .35rem;
}
.test-card .meta svg { width: 14px; height: 14px; opacity: .7; }
.test-card .take-btn {
  margin-top: .5rem;
  padding: .75rem 1rem;
  background: var(--gradient);
  color: #fff; border: 0;
  border-radius: var(--radius);
  font-weight: 600; cursor: pointer;
  font-size: .9rem;
  box-shadow: 0 6px 16px rgba(99,102,241,.28), inset 0 1px 0 rgba(255,255,255,.15);
  transition: transform .15s, box-shadow .15s;
  display: inline-flex; align-items: center; justify-content: center; gap: .5rem;
}
.test-card .take-btn:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 10px 26px rgba(99,102,241,.42);
}
.test-card .take-btn:disabled { opacity: .55; cursor: not-allowed; }

.empty {
  background: var(--c-surface); border: 1px dashed var(--c-border-2);
  border-radius: var(--radius-lg);
  padding: 3rem 2rem; text-align: center; color: var(--c-text-2);
  font-size: .95rem;
  overflow-wrap: break-word; word-break: break-word;
}
.msg { min-height: 1.25rem; font-size: .875rem; color: #dc2626; margin: .5rem 0 0; }

/* -------- Footer -------- */
.site-footer {
  text-align: center; padding: 1.5rem;
  color: var(--c-muted); font-size: .85rem;
  border-top: 1px solid var(--c-border); background: var(--c-surface);
}
.site-footer a { color: var(--c-text-2); text-decoration: none; }
.site-footer a:hover { color: var(--c-primary-dark); }

@media (max-width: 640px) {
  .hero { margin: 2rem auto 1.5rem; }
  .site-header { padding: .7rem 1rem; }
  .page { padding: 0 1rem 3rem; }
  .cat-bar { padding: 0 1rem; }
}