body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background: linear-gradient(135deg, #1e3c72 0%, #2a5298 100%); /* gradient blue */
  color: #f9f9f9;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* === HEADER / NAVIGATION === */
header {
  background: rgba(0,0,0,0.4);
  backdrop-filter: blur(6px);
  padding: 15px 30px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

p {
    margin: 0;
    font-size: 16px;
    color: #5e5656;
    text-align: center;
}

header h1 {
  font-size: 28px;
  margin: 0;
  color: #fff;
  text-align: center;
}

nav a {
  color: #f9f9f9;
  text-decoration: none;
  margin-left: 20px;
  font-weight: bold;
  transition: color 0.2s ease;
}
nav a:hover {
  color: #00ff88;
}
nav a.active {
  color: #ffd700;
  border-bottom: 2px solid #ffd700;
}
.chessboard {
  display: grid;
  grid-template-columns: repeat(8, 80px);
  grid-template-rows: repeat(8, 80px);
  border: 4px solid #333;
  box-shadow: 0 0 10px rgba(0,0,0,0.4);
  user-select: none;
}
.square {
  width: 80px;
  height: 80px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 48px;
  cursor: grab;
}
.dark { background-color: #59753c; }
.light { background-color: #dddd9b; }
.drag-over { outline: 3px dashed #ffcc00; }
#status { margin-top: 15px; font-size: 20px; }
.video-container {
    display: none; /* hidden by default */
    max-width: 800px;
    margin: 1rem auto;
    background: #8d3434;
    padding: 1rem;
    border-radius: 10px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}
video {
    width: 100%;
    height: auto;
    border-radius: 12px;
}
.video-link {
    display: block;
    margin: 1rem auto;
    max-width: 800px;
    font-weight: bold;
    font-size: 1.1rem;
    color: #0077cc;
    text-decoration: none;
    cursor: pointer;
}
.video-link:hover {
    text-decoration: underline;
    color: #1e3c72;
}