/* ostudy.io shared styles: the "Dusk" design (chosen 2026-10-19). */
@font-face { font-family: "IBM Plex Sans"; font-weight: 400; font-display: swap; src: url("/assets/fonts/ibm-plex-sans-latin-400-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 600; font-display: swap; src: url("/assets/fonts/ibm-plex-sans-latin-600-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Sans"; font-weight: 700; font-display: swap; src: url("/assets/fonts/ibm-plex-sans-latin-700-normal.woff2") format("woff2"); }
@font-face { font-family: "IBM Plex Mono"; font-weight: 500; font-display: swap; src: url("/assets/fonts/ibm-plex-mono-latin-500-normal.woff2") format("woff2"); }

:root {
  --bg: #0D0E14; --band: #13141C; --card: #171925; --line: #23252F; --edge: #2C2F3E; --control: #343745;
  --ink: #ECEDF3; --muted: #A7AAB8; --faint: #8A8D9B;
  --rose: #E68DB9; --on-rose: #2A0D1C; --cyan: #7DD3E8; --on-cyan: #062430;
  --wrong: #F29BB0; --hard: #EDC07E; --easy: #92E0B0;
  --mono: "IBM Plex Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body { margin: 0; background: var(--bg); color: var(--ink);
  font: 17px/1.55 "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", sans-serif; }
a { color: var(--cyan); }
a:hover { color: #B5E8F4; }
a:focus-visible, button:focus-visible { outline: 2px solid var(--cyan); outline-offset: 3px; }
img { max-width: 100%; }
h1, h2, h3 { margin: 0; letter-spacing: -0.02em; }
p { margin: 0; }

.wrap { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.band { background: var(--band); border-block: 1px solid var(--line); }
.section { padding-block: 80px; }
.label { font-family: var(--mono); font-weight: 500; font-size: 14px; color: var(--rose); }
.label.cyan { color: var(--cyan); }
.muted { color: var(--muted); }
.h2 { font-size: clamp(1.9rem, 3.4vw, 2.7rem); line-height: 1.08; font-weight: 700; }
.stack { display: flex; flex-direction: column; gap: 16px; }

.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 48px; padding: 0 22px;
  border-radius: 12px; font-weight: 600; font-size: 16px; text-decoration: none; }
.btn.small { min-height: 44px; padding: 0 14px; border-radius: 10px; font-size: 15px; }
.btn.rose { background: var(--rose); color: var(--on-rose); }
.btn.cyan { background: var(--cyan); color: var(--on-cyan); }
.btn.line { border: 1px solid var(--control); color: var(--ink); font-weight: 500; }
.btn:hover { filter: brightness(1.08); }
.btn svg { width: 18px; height: 18px; flex: none; }

/* Top bar */
.top { border-bottom: 1px solid var(--line); }
.top .wrap { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 16px; padding-block: 12px; }
.brand { display: flex; align-items: center; gap: 10px; min-height: 44px; color: var(--ink); text-decoration: none; font-weight: 700; font-size: 20px; }
.brand img { width: 36px; height: 36px; }
.top nav { display: flex; flex-wrap: wrap; flex: 1 1 auto; }
.top nav a { padding: 12px; color: var(--muted); text-decoration: none; font-size: 15px; }
.top nav a:hover { color: var(--ink); }
.top .actions { display: flex; flex-wrap: wrap; gap: 8px; }

/* Hero */
.hero { display: flex; flex-wrap: wrap; align-items: center; gap: 48px; padding-block: 80px 72px; }
.hero .copy { flex: 999 1 520px; min-width: 0; display: flex; flex-direction: column; gap: 22px; }
.hero h1 { font-size: clamp(2.5rem, 5.4vw, 4.2rem); line-height: 1.04; font-weight: 700; letter-spacing: -0.025em; }
.hero .lede { font-size: 1.2rem; color: var(--muted); max-width: 36rem; }
.hero .note { font-size: 14px; color: var(--faint); }
.rule { display: flex; gap: 6px; }
.rule span { height: 4px; border-radius: 2px; }
.buttons { display: flex; flex-wrap: wrap; gap: 12px; }
.mascot { flex: 1 1 300px; display: flex; justify-content: center; }
.mascot div { width: 100%; max-width: 360px; aspect-ratio: 1; border-radius: 32px; background: var(--card); border: 1px solid var(--edge);
  box-shadow: 0 0 0 6px var(--bg), 0 0 0 7px #3B2A3A; display: flex; align-items: center; justify-content: center; }
.mascot img { width: 76%; height: auto; }

/* Cards */
.split { display: flex; flex-wrap: wrap; gap: 48px; align-items: center; }
.split > * { flex: 1 1 380px; min-width: 0; }
.demo { max-width: 520px; display: flex; flex-direction: column; gap: 12px; }
.flash { border-radius: 18px; background: var(--bg); border: 1px solid var(--edge); padding: 30px; min-height: 200px;
  display: flex; flex-direction: column; justify-content: center; gap: 14px; }
.flash .tag { font-family: var(--mono); font-size: 13px; color: var(--faint); }
.flash .q { font-size: 1.45rem; font-weight: 600; }
.flash .a { padding-top: 12px; border-top: 1px dashed var(--control); color: var(--cyan); font-size: 1.15rem; }
.ratings { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 8px; margin: 0; padding: 0; list-style: none; }
.ratings li { min-height: 48px; border-radius: 12px; border: 1px solid var(--control); background: var(--card);
  display: flex; align-items: center; justify-content: center; font-weight: 600; font-size: 15px; }

/* Study plan */
.steps { margin: 0; padding: 0; list-style: none; display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 16px; }
.steps li { border-radius: 18px; background: var(--card); border: 1px solid var(--edge); padding: 24px; display: flex; flex-direction: column; gap: 8px; }
.steps .n { font-family: var(--mono); font-weight: 500; color: var(--rose); font-size: 14px; }
.steps h3 { font-size: 19px; }

/* AI choice */
.choices { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 16px; }
.choice { border-radius: 18px; background: var(--bg); border: 1px solid var(--edge); padding: 26px; display: flex; flex-direction: column; gap: 10px; }
.choice::before { content: ""; width: 32px; height: 4px; border-radius: 2px; background: var(--accent, #5A5E70); }
.choice h3 { font-size: 20px; }

/* Your data */
.data { display: flex; flex-wrap: wrap; gap: 16px 40px; align-items: center; padding-block: 64px; }
.data h2 { flex: 1 1 260px; font-size: 1.7rem; font-weight: 700; }
.chips { flex: 2 1 480px; margin: 0; padding: 0; list-style: none; display: flex; flex-wrap: wrap; gap: 10px; }
.chips li { padding: 12px 16px; border-radius: 12px; background: var(--card); border: 1px solid var(--edge); }

/* Get */
.get { border-radius: 22px; background: var(--card); border: 1px solid #3B2A3A; padding: 36px; display: flex; flex-wrap: wrap; gap: 24px; align-items: center; }
.get > div:first-child { flex: 1 1 320px; display: flex; flex-direction: column; gap: 8px; }
.get h2 { font-size: 1.9rem; font-weight: 700; }

footer { border-top: 1px solid var(--line); margin-top: 80px; }
footer .wrap { display: flex; flex-wrap: wrap; gap: 12px; justify-content: space-between; align-items: center; padding-block: 24px; color: var(--faint); font-size: 14px; }
footer nav { display: flex; flex-wrap: wrap; }
footer nav a { padding: 12px 10px; }

@media (max-width: 600px) {
  .section { padding-block: 56px; }
  .hero { padding-block: 48px 40px; gap: 32px; }
  .mascot div { max-width: 240px; }
  .flash { padding: 22px; }
  .get { padding: 24px; }
}

/* Feature pages */
.top nav a[aria-current="page"] { color: var(--ink); box-shadow: inset 0 -2px 0 var(--rose); }
.page-hero { padding-block: 72px 56px; display: flex; flex-direction: column; gap: 20px; }
.page-hero > * { max-width: 52rem; }
.page-hero h1 { font-size: clamp(2.3rem, 5vw, 3.8rem); line-height: 1.05; font-weight: 700; letter-spacing: -0.025em; }
.page-hero .lede { font-size: 1.2rem; color: var(--muted); }
.features { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; }
.feature { border-radius: 18px; background: var(--card); border: 1px solid var(--edge); padding: 24px; display: flex; flex-direction: column; gap: 8px; }
.band .feature { background: var(--bg); }
.feature h3 { font-size: 19px; }
.feature .tag { align-self: flex-start; font-family: var(--mono); font-weight: 500; font-size: 12px; color: var(--cyan);
  border: 1px solid var(--control); border-radius: 999px; padding: 2px 10px; }
.points { margin: 0; padding-left: 20px; color: var(--muted); display: flex; flex-direction: column; gap: 6px; }
.points strong { color: var(--ink); font-weight: 600; }
.types { margin: 0; padding: 0; list-style: none; display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 10px; }
.types li { padding: 14px 16px; border-radius: 12px; background: var(--card); border: 1px solid var(--edge); display: flex; flex-direction: column; gap: 2px; }
.band .types li { background: var(--bg); }
.types li span { color: var(--muted); font-size: 15px; }
.more { display: inline-flex; align-items: center; gap: 6px; min-height: 44px; font-weight: 600; text-decoration: none; }
.more::after { content: "\2192"; }
.note-line { font-size: 15px; color: var(--faint); max-width: 46rem; }
.next-pages { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.next-pages a { display: flex; flex-direction: column; gap: 4px; padding: 20px; border-radius: 16px; background: var(--card); border: 1px solid var(--edge);
  color: var(--ink); text-decoration: none; min-height: 44px; }
.next-pages a:hover { border-color: var(--rose); }
.next-pages a span { color: var(--muted); font-size: 15px; }
@media (max-width: 600px) { .page-hero { padding-block: 48px 36px; } }