body {
  margin: 0;
  min-height: 100vh;
  font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: radial-gradient(circle at top, #100c26 0%, #09090f 80%);
  color: #eef1ff;
}

.close-btn {
  position: fixed;
  top: 24px;
  right: 24px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.06);
  border: 2px solid rgba(255, 255, 255, 0.14);
  color: #ffffff;
  font-size: 26px;
  line-height: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  cursor: pointer;
  z-index: 9999;
  transition: transform 0.18s ease, background 0.18s ease;
}

.close-btn:hover,
.close-btn:focus {
  transform: scale(1.08);
  background: rgba(255, 255, 255, 0.12);
  outline: none;
}

@media (max-width: 480px) {
  .close-btn {
    top: 16px;
    right: 16px;
    width: 40px;
    height: 40px;
    font-size: 22px;
  }
}

.content {
  padding: 2.5rem 1.5rem 4rem;
  max-width: 1080px;
  margin: 0 auto;
}

.content h1 {
  font-size: clamp(2.4rem, 4vw, 3.6rem);
  margin-bottom: 0.5rem;
}

.content h2 {
  font-size: 1.05rem;
  color: #c9bdf5;
  font-weight: 500;
  margin-bottom: 2rem;
}

.arduino-section {
  background: rgba(255, 255, 255, 0.04);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 36px;
  padding: 2rem;
  box-shadow: 0 36px 90px rgba(0, 0, 0, 0.24);
}

.arduino-section h2 {
  margin: 0 0 1.25rem;
  color: #ffffff;
}

.arduino-grid {
  display: grid;
  gap: 1.75rem;
}

.arduino-card {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 28px;
  padding: 1.75rem;
  box-shadow: 0 24px 70px rgba(0, 0, 0, 0.2);
}

.arduino-card h3 {
  margin: 0 0 1rem;
  font-size: 1.45rem;
  color: #ffffff;
}

.explanation-container p {
  color: #d7d5ef;
  line-height: 1.8;
  margin: 0;
}

.video-container video {
  width: 100%;
  border-radius: 22px;
  box-shadow: 0 22px 55px rgba(0, 0, 0, 0.25);
}

.code-container {
  background: rgba(13, 11, 24, 0.95);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 24px;
  padding: 1rem;
  overflow-x: auto;
}

pre {
  margin: 0;
}

code {
  display: block;
  white-space: pre-wrap;
  word-break: break-word;
  font-family: 'Source Code Pro', Menlo, Monaco, Consolas, 'Courier New', monospace;
  font-size: 0.95rem;
  line-height: 1.7;
  color: #f4f4ff;
}

@media (min-width: 900px) {
  .arduino-grid {
    grid-template-columns: 1.15fr 0.85fr;
    grid-template-areas:
      "explanation video"
      "code code";
  }

  .explanation-card {
    grid-area: explanation;
  }

  .video-card {
    grid-area: video;
  }

  .code-card {
    grid-area: code;
  }
}