:root {
  color-scheme: dark;
  --ink: #e7f6ff;
  --muted: #9ec4d6;
  --water: #071e30;
  --deep: #041524;
  --foam: #d7f4ff;
  --teal: #1ec8d6;
  --teal-deep: #0e7f93;
  --buoy: #f0a202;
  --sail: #f4efe4;
  --line: rgba(158, 220, 236, 0.22);
  --card: rgba(12, 48, 72, 0.82);
  --sb-bg: var(--deep);
  --sb-surface-card: #0e3a56;
  --sb-surface-raised: #124664;
  --sb-surface-inset: #08283c;
  --sb-surface-hover: #16567a;
  --sb-border: rgba(158, 220, 236, 0.35);
  --sb-text-1: var(--ink);
  --sb-text-2: #c5e4f2;
  --sb-text-muted: var(--muted);
  --sb-text-on-brand: #04202a;
  --sb-brand: var(--teal);
  --sb-brand-hover: #7eebf3;
  --sb-brand-light: #9ef0f6;
  --sb-brand-subtle: rgba(30, 200, 214, 0.16);
  --sb-accent: var(--buoy);
  --sb-ok: #3ddc97;
  --sb-warn: var(--buoy);
  --sb-danger: #ff6b6b;
  --sb-info: var(--teal);
  --sb-control-bg: #08283c;
  --sb-control-border: rgba(158, 220, 236, 0.4);
  --sb-control-text: var(--ink);
  --sb-control-radius: 10px;
  --sb-radius: 14px;
  --sb-radius-sm: 10px;
  --sb-radius-lg: 18px;
  --sb-notch: 7px;
  --sb-frame-color: var(--teal);
  --sb-focus-ring: 0 0 0 2px var(--deep), 0 0 0 4px var(--teal);
  --sb-font-body: "Avenir Next", "Segoe UI", system-ui, sans-serif;
  --sb-font-ui: var(--sb-font-body);
  font-family: var(--sb-font-body);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(900px 420px at 80% -10%, rgba(30, 200, 214, 0.18), transparent 60%),
    radial-gradient(700px 380px at -10% 20%, rgba(240, 162, 2, 0.12), transparent 55%),
    linear-gradient(180deg, #0a3148 0%, var(--water) 28%, var(--deep) 100%);
}

.sb-cloak :not(:defined) { visibility: hidden; }

a { color: var(--teal); text-decoration-thickness: 1px; text-underline-offset: 0.18em; }
a:hover { color: var(--foam); }

.top {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.85rem 1.2rem;
  position: sticky;
  top: 0;
  z-index: 5;
  background: rgba(4, 21, 36, 0.82);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(14px);
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  color: var(--foam);
  text-decoration: none;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.brand svg { width: 36px; height: 36px; flex: none; }

.nav-toggle { display: none; }

nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.9rem;
  margin-left: auto;
}

nav a {
  color: var(--muted);
  text-decoration: none;
  font-size: 0.92rem;
  padding: 0.25rem 0;
  border-bottom: 2px solid transparent;
}

nav a:hover, nav a[aria-current="page"] {
  color: var(--foam);
  border-bottom-color: var(--buoy);
}

main {
  width: min(1080px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 1.6rem 0 4rem;
}

h1, h2, h3 { letter-spacing: -0.03em; line-height: 1.15; }
h1 { font-size: clamp(2rem, 4vw, 3.4rem); margin: 0.2rem 0 0.6rem; }
h2 { font-size: 1.25rem; margin: 0 0 0.4rem; }
p { color: var(--muted); line-height: 1.5; }

.hero {
  display: grid;
  grid-template-columns: 1.3fr 0.7fr;
  gap: 1.5rem;
  align-items: center;
  margin-bottom: 1.6rem;
}

.eyebrow {
  margin: 0;
  color: var(--buoy);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.actions { display: flex; flex-wrap: wrap; gap: 0.7rem; margin-top: 1.1rem; }

.mark {
  justify-self: end;
  width: min(100%, 280px);
  filter: drop-shadow(0 18px 30px rgba(0, 0, 0, 0.35));
}

.deck, .lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.9rem;
  margin: 1.2rem 0 1.6rem;
}

.panel {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 1rem 1.1rem;
  box-shadow: 0 16px 40px rgba(0, 0, 0, 0.18);
}

main ul, main ol { list-style: none; padding: 0; display: grid; gap: 0.55rem; }
main li {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0.75rem 0.95rem;
}

form {
  display: grid;
  gap: 0.55rem;
  margin: 0.8rem 0;
  padding: 0.9rem;
  background: rgba(8, 40, 60, 0.55);
  border: 1px solid var(--line);
  border-radius: 14px;
}

label { color: var(--muted); font-size: 0.85rem; }
input, select, textarea {
  width: 100%;
  padding: 0.65rem 0.75rem;
  border-radius: 10px;
  border: 1px solid var(--sb-control-border);
  background: var(--sb-control-bg);
  color: var(--ink);
  font: inherit;
}

button, .button, a.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  width: fit-content;
  padding: 0.65rem 0.95rem;
  border-radius: 999px;
  border: 0;
  background: linear-gradient(180deg, #3ad7e4, var(--teal-deep));
  color: #04202a;
  font: inherit;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
}

button:hover, .button:hover { filter: brightness(1.08); }

table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 0.45rem 0.3rem; border-bottom: 1px solid var(--line); }

.waves { display: block; width: 100%; height: 72px; margin-top: 2rem; }
sb-meter, sb-alert { display: block; margin-top: 0.7rem; }
sb-alert { margin-top: 0; margin-bottom: 1rem; }

@media (max-width: 760px) {
  .hero { grid-template-columns: 1fr; }
  .mark { justify-self: start; width: 180px; }
  .nav-toggle { display: inline-flex; margin-left: auto; }
  nav { display: none; width: 100%; }
  nav[data-open="true"] { display: flex; }
  .top { flex-wrap: wrap; }
}