:root {
  color-scheme: light;
  font-family: "Segoe UI", system-ui, sans-serif;
  font-synthesis: none;
  color: #172b36;
  background: #f7f7f2;
  --ink: #172b36;
  --muted: #52656b;
  --line: #dce0d9;
  --green: #d3ef88;
}
* { box-sizing: border-box; }
body { margin: 0; line-height: 1.5; }
a { color: inherit; text-underline-offset: 4px; }
a:focus-visible { outline: 3px solid #327050; outline-offset: 5px; }
svg { display: block; width: 24px; height: 24px; flex-shrink: 0; }
.site-header, main, footer { width: min(1240px, calc(100% - 80px)); margin-inline: auto; }
.site-header { display: flex; justify-content: space-between; align-items: center; gap: 24px; padding-block: 24px; border-bottom: 1px solid var(--line); }
.brand { display: inline-flex; align-items: center; font-size: 26px; font-weight: 750; letter-spacing: -1px; text-decoration: none; }
.brand-mark { display: grid; place-items: center; width: 46px; height: 46px; margin-right: 12px; border-radius: 12px; background: var(--ink); color: var(--green); }
.brand-mark svg { width: 30px; height: 30px; }
.title-dot { color: #508266; }
.language-switch { display: flex; padding: 4px; border: 1px solid var(--line); border-radius: 12px; gap: 4px; background: #eeefe8; }
.language-switch a { display: grid; place-items: center; min-height: 40px; padding: 8px 16px; border-radius: 8px; font-size: 14px; font-weight: 600; text-decoration: none; }
.language-switch a:hover { background: #e0e5d8; }
.language-switch a[aria-current] { color: #fff; background: var(--ink); }
.intro { display: grid; grid-template-columns: 1fr 310px; align-items: center; gap: 36px; padding-block: 54px 48px; }
.eyebrow { margin: 0 0 14px; font-size: 11px; color: var(--muted); font-weight: 700; letter-spacing: 1.8px; }
h1 { margin: 0; font-size: clamp(36px, 4.4vw, 57px); font-weight: 750; line-height: 1.13; letter-spacing: -2px; }
.lead { max-width: 565px; margin: 20px 0 24px; font-size: 18px; line-height: 1.65; color: var(--muted); }
.collection-nav { display: flex; flex-wrap: wrap; gap: 10px; }
.collection-nav a { display: inline-flex; align-items: center; justify-content: space-between; gap: 28px; min-height: 46px; padding: 10px 18px; border: 1px solid #b2c77e; border-radius: 9px; background: var(--green); font-size: 15px; font-weight: 650; text-decoration: none; }
.collection-nav a:last-child { background: transparent; border-color: #b8c1b4; }
.collection-nav a:hover { background: #c6e17e; }
.intro-art { position: relative; display: grid; place-items: center; height: 265px; border-radius: 50%; background: #edf0e3; }
.art-book { display: grid; place-items: center; width: 142px; height: 146px; border: 1px solid #b8d174; border-radius: 27px 27px 27px 6px; background: var(--green); transform: rotate(-8deg); }
.art-book svg { width: 92px; height: 92px; }
.art-symbol { position: absolute; display: grid; place-items: center; width: 52px; height: 52px; border-radius: 14px; font-size: 32px; font-weight: 650; }
.symbol-plus { top: 15px; left: 32px; background: #e8e1f3; transform: rotate(-12deg); }
.symbol-a { right: 11px; top: 43px; background: #f8e7d6; transform: rotate(12deg); }
.symbol-star { left: 12px; bottom: 59px; color: #508266; font-size: 44px; }
.symbol-equals { right: 24px; bottom: 50px; background: #dfeef0; transform: rotate(-9deg); }
.art-caption { position: absolute; bottom: 5px; padding: 8px 16px; border: 1px solid var(--line); border-radius: 30px; background: #fffef8; font-size: 12px; color: var(--muted); }
.collection { scroll-margin-top: 24px; }
.collection + .collection { margin-top: 48px; }
.collection-heading { display: flex; align-items: center; justify-content: space-between; gap: 24px; margin-bottom: 22px; padding-top: 24px; border-top: 1px solid var(--line); }
.heading-main { display: flex; align-items: center; gap: 16px; }
.collection-mark { display: grid; place-items: center; width: 54px; height: 58px; flex-shrink: 0; border: 1px solid #b8d174; border-radius: 13px 13px 13px 3px; background: var(--green); font-size: 17px; font-weight: 750; letter-spacing: 1px; }
.mark-hu { background: #e8e1f3; border-color: #d4c7e6; }
h2 { margin: 0; font-size: 28px; line-height: 1.25; letter-spacing: -.7px; }
.collection-heading p { margin: 5px 0 0; color: var(--muted); font-size: 15px; }
.lesson-count { display: flex; align-items: center; gap: 8px; flex-shrink: 0; font-size: 23px; font-weight: 650; }
.lesson-count span { color: var(--muted); font-size: 13px; font-weight: 400; }
.lessons { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 24px; }
.lesson { display: flex; flex-direction: column; min-width: 0; border: 1px solid var(--line); border-radius: 18px; background: #fff; transition: border-color .18s ease, box-shadow .18s ease; }
.lesson:hover { border-color: #a8b9a4; box-shadow: 0 8px 28px #172b360a; }
.cover { aspect-ratio: 16 / 9; overflow: hidden; border-radius: 17px 17px 0 0; border-bottom: 1px solid #172b3610; }
.cover img { display: block; width: 100%; height: 100%; object-fit: contain; }
.cover-subtraktion { background: #e8e1f3; }
.cover-raketen { background: #f8e7d6; }
.cover-wasser { background: #dfeef0; }
.cover-namen { background: #e5ecd5; }
.lesson-info { flex: 1; display: flex; flex-direction: column; padding: 22px; }
.lesson-label { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 8px; font-size: 12px; color: var(--muted); }
.lesson-label > :first-child { font-weight: 650; }
.language-tag { border: 1px solid var(--line); border-radius: 5px; padding: 2px 7px; font-size: 11px; }
h3 { margin: 13px 0 4px; font-size: 23px; font-weight: 700; line-height: 1.25; letter-spacing: -.55px; overflow-wrap: break-word; }
.lesson-subtitle { margin: 0 0 13px; color: #405f4d; font-size: 14px; font-weight: 600; }
.description { margin: 0 0 18px; color: var(--muted); font-size: 15px; line-height: 1.65; }
.tags { display: flex; flex-wrap: wrap; gap: 7px; list-style: none; padding: 0; margin: auto 0 20px; }
.tags li { padding: 5px 9px; border-radius: 6px; background: #f2f4ed; color: #435851; font-size: 12px; }
.button { display: flex; align-items: center; justify-content: space-between; gap: 12px; min-height: 50px; padding: 12px 16px; border: 1px solid var(--ink); border-radius: 9px; background: var(--ink); color: #fff; font-size: 15px; line-height: 1.35; font-weight: 600; text-decoration: none; }
.button svg { width: 19px; height: 19px; }
.button:hover { background: #304d5e; border-color: #304d5e; }
.lessons-hu { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.lessons-hu .lesson { display: grid; grid-template-columns: 34% 1fr; }
.lessons-hu .cover { aspect-ratio: auto; height: 100%; border-radius: 17px 0 0 17px; border-bottom: 0; border-right: 1px solid #172b3610; }
.lessons-hu .cover img { object-fit: contain; transform: scale(1.6); }
.lessons-hu h3 { font-size: 21px; }
.help { margin-top: 44px; padding: 28px; border: 1px solid var(--line); border-radius: 18px; background: #eef1e8; }
.help h2 { font-size: 23px; margin-bottom: 24px; }
.help ol { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 30px; margin: 0; padding: 0; list-style: none; counter-reset: steps; }
.help li { counter-increment: steps; }
.help li::before { content: '0' counter(steps); color: #405f4d; font-size: 12px; font-weight: 700; letter-spacing: 1px; }
.help h3 { margin: 9px 0 7px; font-size: 17px; letter-spacing: -.2px; }
.help p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.65; }
footer { display: flex; align-items: center; justify-content: space-between; gap: 24px; margin-top: 40px; padding-block: 25px 32px; border-top: 1px solid var(--line); font-size: 13px; color: var(--muted); }
footer p { margin: 0; }
footer a { flex-shrink: 0; padding-block: 10px; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }
.skip-link { position: absolute; top: 12px; left: 16px; padding: 12px 18px; background: var(--ink); color: #fff; border-radius: 8px; z-index: 1; transform: translateY(-180%); }
.skip-link:focus { transform: translateY(0); }
@media (max-width: 1100px) {
  .site-header, main, footer { width: calc(100% - 48px); }
  .lessons { gap: 18px; }
  .lesson-info { padding: 18px; }
  .lessons-hu .lesson { display: flex; }
  .lessons-hu .cover { aspect-ratio: 16 / 9; height: auto; border-radius: 17px 17px 0 0; border-right: 0; border-bottom: 1px solid #172b3610; }
  .lessons-hu .cover img { transform: none; }
}
@media (max-width: 850px) {
  .intro { grid-template-columns: 1fr 220px; gap: 24px; }
  .intro-art { height: 220px; }
  .symbol-a { right: -4px; top: 14px; }
  .symbol-plus { left: 0; top: 0; }
  .symbol-equals { right: -2px; bottom: 35px; }
  .symbol-star { left: -8px; bottom: 30px; }
  .lessons { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .help ol { gap: 20px; }
}
@media (max-width: 600px) {
  .site-header, main, footer { width: calc(100% - 32px); }
  .site-header { align-items: flex-start; flex-wrap: wrap; gap: 16px; padding-block: 18px; }
  .brand { font-size: 23px; }
  .brand-mark { width: 40px; height: 40px; }
  .language-switch { margin-left: auto; }
  .language-switch a { padding-inline: 14px; }
  .intro { grid-template-columns: 1fr; padding-block: 32px; }
  .intro-art { display: none; }
  h1 { font-size: clamp(34px, 8vw, 44px); letter-spacing: -1.3px; }
  .eyebrow { font-size: 10px; letter-spacing: 1.3px; }
  .lead { font-size: 17px; margin-top: 16px; }
  .collection-heading { align-items: flex-start; gap: 14px; }
  .heading-main { gap: 12px; }
  .collection-mark { width: 43px; height: 49px; font-size: 14px; }
  h2 { font-size: 25px; }
  .collection-heading p { font-size: 14px; }
  .lesson-count { font-size: 19px; padding-top: 4px; }
  .lesson-count span { display: none; }
  .lessons { grid-template-columns: 1fr; gap: 20px; }
  .lesson-info { padding: 22px; }
  h3, .lessons-hu h3 { font-size: 23px; }
  .collection + .collection { margin-top: 34px; }
  .help { padding: 23px; margin-top: 32px; }
  .help ol { grid-template-columns: 1fr; gap: 24px; }
  footer { align-items: flex-start; flex-direction: column; gap: 10px; margin-top: 30px; }
}
@media (prefers-reduced-motion: reduce) { .lesson { transition: none; } }