:root {
  --color-text: #111;
  --color-secondary: #666;
  --color-accent: #0057FF;
  --color-grid-bg: #FAFAFA;
  --color-border: #d1d5db;
  --color-conflict: #ef4444;
  --color-conflict-bg: #fee2e2;
}

.dark {
  --color-text: #EEEEEE;
  --color-secondary: #BBBBBB;
  --color-accent: #4A90E2;
  --color-grid-bg: #1E1E1E;
  --color-border: #3A3A3A;
  --color-conflict: #ff6b6b;
  --color-conflict-bg: #3a1f1f;
  background: #1E1E1E;
}

html, body {
  font-family: Inter, Roboto, system-ui, -apple-system, "Segoe UI", Helvetica, Arial, "Noto Sans", sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  margin: 0;
  background: #fff;
}

.secondary { color: var(--color-secondary); }
.accent { color: var(--color-accent); }

.nav-bar {
  position: fixed;
  top: 0; left: 0; right: 0;
  background: #fff;
  border-bottom: 1px solid var(--color-border);
  height: 64px;
  z-index: 50;
}
.nav-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: flex-start;
  height: 64px;
}
.logo { font-weight: 700; font-size: 18px; color: var(--color-accent); text-decoration: none; }
.logo:hover { text-decoration: underline; }

.main-wrap { padding-top: 88px; }
.container {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
}

.hero { padding: 32px 0; }
.title { font-size: 28px; font-weight: 600; margin: 0 0 8px; }
.subtitle { font-size: 16px; margin: 0; }

.grid-section { padding: 24px 0; }
.grid-bg { background: var(--color-grid-bg); border-radius: 12px; padding: 24px; }
.placeholder { height: 240px; border: 1px dashed #d1d5db; border-radius: 12px; display: flex; align-items: center; justify-content: center; color: var(--color-secondary); }

@media (max-width: 640px) {
  .main-wrap { padding-top: 76px; }
  .nav-inner { padding: 0 16px; }
  .container { padding: 0 16px; }
  .title { font-size: 24px; }
}

.cards {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}
.card {
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 20px;
  cursor: pointer;
  transition: box-shadow .2s ease, border-color .2s ease, transform .1s ease;
}
.card:hover { border-color: var(--color-accent); box-shadow: 0 6px 24px rgba(0,0,0,0.06); transform: translateY(-1px); }
.card-title { font-size: 18px; font-weight: 600; margin: 0 0 8px; color: var(--color-text); }
.card-desc { font-size: 16px; color: var(--color-secondary); margin: 0; }
.card-row { margin-top: 8px; display: flex; align-items: center; gap: 8px; }
.cta { display: inline-flex; align-items: center; gap: 8px; color: var(--color-accent); font-weight: 500; }

@media (max-width: 768px) {
  .cards { grid-template-columns: 1fr; }
}

.game-header { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin-bottom: 16px; }
.difficulty { font-size: 16px; font-weight: 600; color: var(--color-text); }
.btn { display: inline-flex; align-items: center; justify-content: center; padding: 10px 14px; border-radius: 10px; border: 1px solid var(--color-border); background: #fff; color: var(--color-text); font-weight: 500; cursor: pointer; transition: background-color .15s ease, border-color .15s ease, transform .15s ease, opacity .15s ease; }
.btn:hover { background: #eff6ff; }
.btn-primary { background: var(--color-accent); border-color: var(--color-accent); color: #fff; }
.btn-primary:hover { background: var(--color-accent); filter: brightness(1.08); }
.dark .btn { background: #2a2a2a; }

.game-wrap { display: grid; grid-template-columns: 1fr 320px; gap: 24px; align-items: start; }
.game-main { background: var(--color-grid-bg); border-radius: 12px; padding: 24px; display: flex; align-items: center; justify-content: center; }
.sudoku-grid { width: 540px; height: 540px; display: grid; grid-template-columns: repeat(9, 1fr); grid-template-rows: repeat(9, 1fr); background: #fff; border-radius: 12px; box-shadow: 0 1px 4px rgba(0,0,0,0.06); position: relative; opacity: 0; animation: fadeInGrid .3s ease forwards; }
.dark .sudoku-grid { background: #2a2a2a; }
.sudoku-cell { border: 1px solid #d1d5db; display: flex; align-items: center; justify-content: center; font-size: 18px; color: var(--color-text); }
.sudoku-grid::before, .sudoku-grid::after { content: ""; position: absolute; inset: 0; pointer-events: none; }
.sudoku-grid::before { box-shadow: inset 0 0 0 2px var(--color-border); border-radius: 12px; }
.sudoku-grid::after { box-shadow: inset 0 0 0 0 #000; }
.game-side { border: 1px solid var(--color-border); border-radius: 12px; background: #fff; padding: 16px; min-height: 240px; }
.dark .game-side { background: #2a2a2a; }

.page-fit { min-height: calc(100vh - 88px); display: flex; flex-direction: column; }

@media (max-width: 1024px) {
  .sudoku-grid { width: 440px; height: 440px; }
}
@media (max-width: 768px) {
  .game-wrap { grid-template-columns: 1fr; }
  .game-side { order: 2; }
  .game-main { order: 1; }
  .sudoku-grid { width: 92vw; height: 92vw; }
}

/* Animations */
@keyframes fadeInGrid { from { opacity: 0 } to { opacity: 1 } }
@keyframes selectPulse { 0% { background: transparent } 100% { background: rgba(219,234,254,0.6) } }
@keyframes placePop { 0% { transform: scale(0.9); opacity: 0.6 } 100% { transform: scale(1); opacity: 1 } }
@keyframes modalIn { 0% { opacity: 0; transform: scale(0.98) } 100% { opacity: 1; transform: scale(1) } }

.tooltip { position: fixed; background: #fff; color: var(--color-text); border: 1px solid var(--color-border); border-radius: 8px; padding: 6px 8px; font-size: 12px; box-shadow: 0 1px 4px rgba(0,0,0,0.06); z-index: 60; }
.dark .tooltip { background: #2a2a2a; }

/* SEO content blocks */
.seo-block {
  width: 80%;
  margin: 32px auto 0;
  background: #FAFAFA;
  border-radius: 12px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.05);
  padding: 24px;
  font-size: 16px;
  line-height: 1.6;
  color: #333;
  opacity: 0;
  animation: seoFade .35s ease-in forwards;
}
.seo-diff {
  width: 100%;
  background: #F8F8F8;
  border-radius: 12px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.05);
  padding: 20px;
  margin-bottom: 24px;
  font-size: 16px;
  line-height: 1.5;
  color: #333;
  opacity: 0;
  animation: seoFade .3s ease forwards;
}
.seo-game {
  width: 100%;
  background: #FFFFFF;
  border-left: 4px solid var(--color-accent);
  border-radius: 8px;
  padding: 12px;
  margin-bottom: 16px;
  font-size: 14px;
  color: #555;
  opacity: 0;
  animation: seoFade .25s ease forwards;
}
@keyframes seoFade { from { opacity: 0; transform: translateY(4px) } to { opacity: 1; transform: translateY(0) } }

@media (max-width: 640px) {
  .seo-block { width: 95%; font-size: 15px; padding: 16px; }
  .seo-diff { font-size: 15px; padding: 16px; }
  .seo-game { font-size: 13px; padding: 10px; }
}
.btn-new { min-width: 150px; height: 50px; }
.desktop-only { display: inline-flex; }
.mobile-only { display: none; }
@media (max-width: 768px) {
  .btn-new { width: 100%; height: 48px; }
  .desktop-only { display: none; }
  .mobile-only { display: inline-flex; width: 100%; }
}

.breadcrumb { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--color-secondary); margin: 8px 0 0; }
.breadcrumb a { color: var(--color-secondary); text-decoration: none; }
.breadcrumb a:hover { color: var(--color-accent); text-decoration: underline; }
.crumb-middle { max-width: 40vw; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
@media (max-width: 640px) {
  .crumb-middle { max-width: 50vw; }
}

.nav-right { display: flex; align-items: center; gap: 12px; }
.dropdown { position: relative; }
.dropdown-trigger { display: inline-flex; align-items: center; gap: 6px; padding: 8px 12px; border-radius: 10px; border: 1px solid var(--color-border); background: #fff; color: var(--color-text); cursor: pointer; }
.dropdown-menu { position: absolute; top: 100%; right: 0; min-width: 160px; background: #fff; border: 1px solid var(--color-border); border-radius: 10px; box-shadow: 0 8px 24px rgba(0,0,0,0.08); padding: 8px; display: none; }
.dropdown:hover .dropdown-menu, .dropdown:focus-within .dropdown-menu { display: block; }
.dropdown-menu a { display: block; padding: 8px 10px; border-radius: 8px; color: var(--color-text); text-decoration: none; }
.dropdown-menu a:hover { background: #eff6ff; color: var(--color-accent); }
.dark .dropdown-trigger { background: #2a2a2a; }
.dark .dropdown-menu { background: #2a2a2a; }
.dropdown-trigger, .channel-link.btn { font-size: 14px; }
.nav-channels { display: flex; align-items: center; gap: 8px; margin-left: 16px; }
.channel-link.btn { padding: 8px 12px; }