/* system-design-road.css */
:root {
  --sys-purple: #a855f7;
  --sys-indigo: #6366f1;
  --glass-bg: rgba(10, 10, 10, 0.9);
}

.centered-header {
  text-align: center;
  margin-top: 100px;
  margin-bottom: 50px;
}

.roadmap-wrapper {
  position: relative;
  max-width: 1100px;
  margin: 0 auto;
  padding: 40px 20px;
  min-height: 100vh;
}

.roadmap-spine {
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 3px;
  background: linear-gradient(
    to bottom,
    transparent,
    var(--sys-purple),
    var(--sys-indigo),
    transparent
  );
  transform: translateX(-50%);
  z-index: 0;
}

.roadmap-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 60px;
  width: 100%;
}

.chapter-node {
  position: relative;
  width: 44%;
  background: var(--glass-bg);
  border: 1px solid #333;
  border-radius: 20px;
  padding: 30px;
  backdrop-filter: blur(12px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  z-index: 1;
  transition:
    transform 0.3s ease,
    border-color 0.3s ease;
}

.chapter-node.left {
  align-self: flex-start;
  text-align: right;
}
.chapter-node.right {
  align-self: flex-end;
  text-align: left;
}

.chapter-node:hover {
  border-color: var(--sys-purple);
  transform: translateY(-5px);
}

.chapter-node::after {
  content: '';
  position: absolute;
  top: 35px;
  width: 16px;
  height: 16px;
  background: var(--sys-purple);
  border-radius: 50%;
  box-shadow: 0 0 12px var(--sys-purple);
}
.chapter-node.left::after {
  right: -13.5%;
}
.chapter-node.right::after {
  left: -13.5%;
}

.node-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}
.chapter-node.left .node-header {
  flex-direction: row-reverse;
}

.node-header h3 {
  color: var(--sys-purple);
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.2rem;
  margin: 0;
}

.toggle-btn {
  background: rgba(168, 85, 247, 0.1);
  border: 1px solid var(--sys-purple);
  color: var(--sys-purple);
  width: 35px;
  height: 35px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 1.3rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: 0.3s;
}

.toggle-btn.active {
  background: var(--sys-purple);
  color: #000;
  transform: rotate(45deg);
}

.chapter-details {
  max-height: 0;
  overflow: hidden;
  transition:
    max-height 0.5s cubic-bezier(0.4, 0, 0.2, 1),
    opacity 0.3s;
  opacity: 0;
}

.chapter-details.open {
  max-height: 1000px;
  opacity: 1;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid #222;
}

.module-link {
  display: block;
  color: #999;
  text-decoration: none;
  padding: 12px;
  margin: 8px 0;
  background: rgba(255, 255, 255, 0.03);
  border-radius: 8px;
  transition: 0.3s;
}

.module-link:hover {
  color: #fff;
  background: rgba(168, 85, 247, 0.2);
  padding-left: 20px;
}

@media (max-width: 768px) {
  .roadmap-spine {
    left: 20px;
  }
  .chapter-node {
    width: 85%;
    align-self: flex-end;
    text-align: left;
  }
  .chapter-node.left .node-header {
    flex-direction: row;
  }
  .chapter-node.left::after,
  .chapter-node.right::after {
    left: -34px;
  }
}