:root {
  --bg: #f4f7fb;
  --surface: #ffffff;
  --surface-2: #eef3fa;
  --text: #13233a;
  --muted: #4a5c75;
  --primary: #0077b6;
  --primary-2: #00a6fb;
  --accent: #ffb703;
  --ok: #1a936f;
  --warn: #d62828;
  --shadow: 0 12px 30px rgba(19, 35, 58, 0.1);
  --radius: 16px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 100% 0%, rgba(0, 166, 251, 0.15), transparent 40%),
    radial-gradient(circle at 0% 100%, rgba(255, 183, 3, 0.15), transparent 45%),
    var(--bg);
  line-height: 1.6;
}

.skip-link {
  position: absolute;
  left: -9999px;
}
.skip-link:focus {
  left: 12px;
  top: 12px;
  background: var(--text);
  color: #fff;
  padding: 8px 12px;
  border-radius: 8px;
}

.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  justify-content: center;
  background: rgba(19, 35, 58, 0.95);
  backdrop-filter: blur(8px);
  padding: 12px;
}

.navbar a {
  color: #f1f7ff;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 8px 12px;
  border-radius: 999px;
  transition: background 0.2s ease;
}

.navbar a:hover,
.navbar a[aria-current='page'] {
  background: rgba(255, 255, 255, 0.18);
}

.nav-drop {
  position: relative;
}

.nav-drop > summary {
  list-style: none;
  color: #f1f7ff;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 8px 12px;
  border-radius: 999px;
  cursor: pointer;
}

.nav-drop > summary::-webkit-details-marker {
  display: none;
}

.nav-drop > summary:hover {
  background: rgba(255, 255, 255, 0.18);
}

.nav-drop[open] > summary {
  background: rgba(255, 255, 255, 0.22);
}

.nav-drop .nav-menu {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  min-width: 220px;
  display: grid;
  gap: 4px;
  background: #102843;
  border: 1px solid rgba(150, 210, 255, 0.3);
  border-radius: 12px;
  padding: 8px;
  box-shadow: 0 12px 26px rgba(0, 0, 0, 0.25);
}

.nav-drop .nav-menu a {
  padding: 8px 10px;
  border-radius: 8px;
  font-size: 0.9rem;
}

@media (max-width: 760px) {
  .nav-drop {
    width: 100%;
  }

  .nav-drop > summary {
    width: 100%;
    text-align: center;
  }

  .nav-drop .nav-menu {
    position: static;
    min-width: 100%;
    margin-top: 6px;
  }
}

.container {
  width: min(1100px, 92%);
  margin: 30px auto 80px;
}

.home-main {
  width: min(1400px, 96%);
}

.home-main .hero {
  padding: 14px 18px;
  border-radius: 16px;
  display: grid;
  grid-template-columns: 1fr auto;
  column-gap: 18px;
  row-gap: 4px;
  align-items: center;
}

.home-main .hero h1 {
  margin: 0 0 6px;
  font-size: clamp(1.15rem, 2vw, 1.55rem);
  line-height: 1.2;
  grid-column: 1;
  grid-row: 2;
}

.home-main .hero p {
  margin: 0 0 10px;
  font-size: 1rem;
  line-height: 1.35;
  max-width: none;
  grid-column: 1;
  grid-row: 3;
}

.home-main .hero .kicker {
  grid-column: 1;
  grid-row: 1;
  margin-bottom: 2px;
  font-size: 0.72rem;
  padding: 5px 5px;
  width: fit-content;
  justify-self: start;
}

.home-main .hero .button {
  grid-column: 2;
  grid-row: 1 / span 3;
  align-self: center;
  white-space: nowrap;
}

@media (max-width: 820px) {
  .home-main .hero {
    display: block;
  }
}

.hero {
  background: linear-gradient(135deg, #023e8a, #0077b6 60%, #00a6fb);
  color: white;
  border-radius: 24px;
  padding: 32px;
  box-shadow: var(--shadow);
}

.hero h1 { margin-top: 0; font-size: clamp(1.7rem, 3.2vw, 2.6rem); }
.hero p { max-width: 70ch; }

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}

.card {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
}

.card h2, .card h3 { margin-top: 0; }

.kicker {
  display: inline-block;
  margin-bottom: 10px;
  background: #e6f4ff;
  color: #045c88;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 700;
  padding: 4px 10px;
}

.idea {
  border-left: 6px solid var(--accent);
  background: #fff7e8;
}

.check-list li { margin-bottom: 8px; }

.button,
button {
  border: none;
  border-radius: 10px;
  background: var(--primary);
  color: #fff;
  padding: 10px 14px;
  font-weight: 700;
  cursor: pointer;
  text-decoration: none;
  display: inline-block;
}

.button:hover,
button:hover { background: #026494; }

.secondary {
  background: #dbe9fb;
  color: #10304f;
}
.secondary:hover { background: #c1ddfa; }

.prev-next {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 28px;
}

.prev-next a { min-width: 120px; text-align: center; }

.table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.table th, .table td {
  border: 1px solid #d0deef;
  padding: 10px;
}
.table th { background: #e8f1fc; }

.activity-option {
  display: block;
  margin: 8px 0;
  width: 100%;
  text-align: left;
}

.feedback { font-weight: 700; margin-top: 8px; }
.feedback.ok { color: var(--ok); }
.feedback.bad { color: var(--warn); }

.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 12px;
  align-items: end;
}

input[type='number'] {
  width: 100%;
  padding: 10px;
  border-radius: 10px;
  border: 1px solid #a9bfdc;
}

.exercise {
  border: 1px solid #d6e3f3;
  border-radius: var(--radius);
  padding: 16px;
  background: var(--surface);
}

.exercise + .exercise { margin-top: 14px; }
.solution {
  display: none;
  margin-top: 12px;
  padding: 12px;
  border-radius: 12px;
  background: #eef8f3;
  border: 1px solid #b5e3ce;
}
.solution.visible { display: block; }

.canvas-wrap {
  margin-top: 12px;
  background: #f1f6fd;
  border-radius: 12px;
  padding: 8px;
}
canvas {
  width: 100%;
  height: auto;
  display: block;
  background: white;
  border-radius: 8px;
}

.level-title {
  margin-top: 26px;
  border-bottom: 3px solid #c6ddf6;
  padding-bottom: 6px;
}

footer {
  text-align: center;
  color: var(--muted);
  padding: 30px 10px 60px;
}

@media (max-width: 680px) {
  .hero { padding: 22px; }
  .prev-next { flex-direction: column; }
  .prev-next a { width: 100%; }
}

.media-card {
  padding: 12px;
}

.visual {
  width: 100%;
  height: auto;
  border-radius: 14px;
  display: block;
  box-shadow: 0 10px 24px rgba(20, 47, 78, 0.14);
  cursor: zoom-in;
}

.visual-caption {
  margin: 10px 6px 2px;
  color: var(--muted);
  font-size: 0.95rem;
}

.photo-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 12px;
  margin-top: 16px;
}

.photo-card {
  background: var(--surface);
  border-radius: 14px;
  overflow: hidden;
  box-shadow: var(--shadow);
  border: 1px solid #d9e6f5;
}

.photo-card img {
  width: 100%;
  height: 180px;
  object-fit: cover;
  display: block;
  cursor: zoom-in;
}

.photo-card p {
  margin: 0;
  padding: 10px 12px;
  font-size: 0.9rem;
  color: var(--muted);
}

.banner-img {
  width: 100%;
  height: 260px;
  object-fit: cover;
  border-radius: 16px;
  box-shadow: var(--shadow);
}

.inline-link-card {
  margin-top: 16px;
  border: 1px solid #cde0f6;
  background: #eef6ff;
}

.home-gallery {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 18px;
  margin-top: 18px;
}

.home-visual-card {
  background: #fff;
  border-radius: 18px;
  overflow: hidden;
  box-shadow: var(--shadow);
  border: 1px solid #d8e6f7;
}

.home-visual-image {
  width: 100%;
  height: clamp(300px, 32vw, 440px);
  object-fit: cover;
  display: block;
  cursor: zoom-in;
}

.home-visual-card p {
  margin: 0;
  padding: 14px 16px 16px;
  font-size: 1.03rem;
  color: #173a5c;
}

@media (max-width: 980px) {
  .home-gallery {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 680px) {
  .home-gallery {
    grid-template-columns: 1fr;
  }
}

.intro-split {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 16px;
  align-items: center;
}

.intro-split .intro-image {
  width: 100%;
  max-height: 420px;
  object-fit: cover;
  border-radius: 14px;
  box-shadow: var(--shadow);
}

.lightbox {
  position: fixed;
  inset: 0;
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 0;
  background: rgba(8, 20, 36, 0.9);
}

.lightbox.open {
  display: flex;
}

.lightbox img {
  width: 100vw;
  height: 100vh;
  max-width: 100vw;
  max-height: 100vh;
  object-fit: contain;
  border-radius: 0;
  box-shadow: 0 16px 36px rgba(0, 0, 0, 0.45);
}

.lightbox-close {
  position: absolute;
  top: 16px;
  right: 16px;
  border: none;
  border-radius: 999px;
  width: 42px;
  height: 42px;
  font-size: 1.6rem;
  line-height: 1;
  color: #fff;
  background: rgba(255, 255, 255, 0.2);
  cursor: pointer;
}

@media (max-width: 900px) {
  .intro-split {
    grid-template-columns: 1fr;
  }
}