:root {
  --color-bg: #181c25;
  --color-primary: #4fc3f7;
  --color-accent: #ffb300;
  --color-panel: #23283a;
  --color-text: #fff;
  --color-btn: #4fc3f7;
  --color-btn-hover: #0288d1;
  --color-score: #ffb300;
  --font-main: 'Segoe UI', Arial, sans-serif;
  --border-radius: 0.5rem;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-main);
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 2rem;
  background: var(--color-panel);
}
.header__logo {
  width: 40px;
  height: 40px;
  background: var(--color-primary);
  border-radius: 0.25rem;
  margin-right: 1rem;
}
.header__title {
  font-size: 2rem;
  margin: 0 1rem 0 0;
}
.nav__list {
  display: flex;
  gap: 1rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav__link {
  color: var(--color-text);
  text-decoration: none;
  font-size: 1rem;
  padding: 0.5em 1em;
  border-radius: var(--border-radius);
  transition: background 0.2s;
}
.nav__link:hover,
.nav__link:focus {
  background: var(--color-primary);
  color: #222;
  outline: none;
}

.main {
  flex: 1 1 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: flex-start;
  gap: 2rem;
  padding: 2rem 1rem;
}
.tetris-game {
  background: var(--color-panel);
  border-radius: var(--border-radius);
  padding: 2rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}
.tetris-game__canvas {
  background: #111;
  border: 2px solid var(--color-primary);
  border-radius: var(--border-radius);
  display: block;
  margin-bottom: 1.5rem;
  outline: none;
}
.tetris-game__panel {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  width: 100%;
  align-items: center;
}
.tetris__score {
  font-size: 1.25rem;
  color: var(--color-score);
}
.tetris__next {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
#next-canvas {
  background: #222;
  border: 1px solid var(--color-accent);
  border-radius: var(--border-radius);
}
.tetris__controls {
  display: flex;
  gap: 1rem;
}
.tetris__btn {
  background: var(--color-btn);
  color: var(--color-text);
  border: none;
  border-radius: var(--border-radius);
  padding: 0.5em 1.5em;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.2s;
}
.tetris__btn:focus {
  outline: 2px solid var(--color-accent);
}
.tetris__btn:hover {
  background: var(--color-btn-hover);
}

.tetris-sidebar {
  background: var(--color-panel);
  border-radius: var(--border-radius);
  padding: 2rem 1.5rem;
  min-width: 220px;
  max-width: 300px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
  display: flex;
  flex-direction: column;
  gap: 2rem;
}
.tetris-sidebar__rules h2,
.tetris-sidebar__leaderboard h2 {
  font-size: 1.2rem;
  margin-bottom: 0.5rem;
}
.tetris-sidebar__rules ul {
  padding-left: 1.2em;
  margin: 0;
}
.tetris-sidebar__leaderboard ol {
  padding-left: 1.2em;
  margin: 0;
}

.footer {
  background: var(--color-panel);
  color: var(--color-text);
  text-align: center;
  padding: 1rem 0;
  font-size: 0.9rem;
}

@media (max-width: 900px) {
  .main {
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
  }
  .tetris-sidebar {
    max-width: 100%;
    min-width: 0;
    width: 100%;
    margin-top: 1.5rem;
  }
}

@media (max-width: 600px) {
  .header {
    flex-direction: column;
    gap: 0.5rem;
    padding: 1rem;
  }
  .main {
    padding: 1rem 0.5rem;
  }
  .tetris-game {
    padding: 1rem;
  }
  .tetris-sidebar {
    padding: 1rem;
  }
  .tetris-game__canvas {
    width: 180px;
    height: 300px;
  }
  #next-canvas {
    width: 60px;
    height: 60px;
  }
}