:root {
  --primary-color: #252839;
  --secondary-color: #2b2e3f;
  --border-color: #4b4e5f;
  --text-color2: #f6f6f6;
}
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
body {
  background-color: var(--primary-color);
}

/* Certificates */
#roadmap-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.8rem;
  padding: 0 1rem 50px 1rem;
}
.roadmap-tile {
  display: block;
  border: 2px solid var(--border-color);
  border-radius: 8px;
  width: 80vw;
  max-width: 700px;
  height: auto;
  text-align: center;
  background-color: var(--secondary-color);
  overflow: hidden;
}
.roadmap-image {
  display: block;
  width: 100%;
  height: 100%;
  margin: 0 auto;
  object-fit: cover;
}

/* Scroll-to-top */
#back-to-top {
  z-index: 999;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}
#back-to-top.show {
  opacity: 1;
  visibility: visible;
}
#arrow-circle {
  border-radius: 50%;
  font-size: clamp(2.8rem, 5vw, 3rem);
  color: var(--text-color2);
  background-color: var(--primary-color);
  opacity: 0.75;
}
#arrow-circle:hover {
  opacity: 1;
  transition: opacity 0.2s ease-in-out;
}