section {
  scroll-margin-top: 70px;
}

/* Hero background image */
.hero {
  height: 100vh;
  background-image: url("images/airdrum_hero.jpg");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  display: flex;
  align-items: center;
  justify-content: center;

  position: relative;   /* ← ADD THIS */
}

/* once user scrolls past hero */
body:not(:has(.hero:hover)) .topnav {
  opacity: 1;
  pointer-events: auto;
}

/* Fade hero image into page content */
.hero::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 180px;
  background: linear-gradient(
    to bottom,
    rgba(0, 0, 0, 0),
    #ffffff
  );
}

.hero-overlay {
  background: rgba(0, 0, 0, 0.55); /* dark overlay for readability */
  color: white;
  padding: 2rem 3rem;
  text-align: center;
  border-radius: 8px;
}

.hero-overlay h1 {
  font-size: 3rem;
  margin-bottom: 0.5rem;
}

.hero-overlay p {
  font-size: 1.2rem;
  margin: 0.3rem 0;
}



body {
  font-family: Arial, Helvetica, sans-serif;
  margin: 0;
  padding: 0;
  line-height: 1.6;
}

.topnav {
  position: fixed;
  top: 0;
  width: 100%;
  background: rgba(0, 0, 0, 0.85);
  padding: 0.5rem;
  z-index: 1000;

  /* fade-in behavior */
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.5s ease;
}

.topnav a {
  color: white;
  text-decoration: none;
  padding: 0.5rem 0.8rem;
  display: inline-block;
}


.topnav a {
  color: white;
  text-decoration: none;
  padding: 0.5rem 0.8rem;
  display: inline-block;
}

.topnav a:hover {
  background-color: #555;
}

section {
  max-width: 900px;
  margin: auto;
  padding: 2rem 1rem;
  border-bottom: 1px solid #eee;
}

h1, h2, h3 {
  margin-top: 0;
}

figure {
  text-align: center;
}

figcaption {
  font-size: 0.9em;
  color: #555;
}

footer {
  text-align: center;
  padding: 1rem;
  color: #777;
}

/* Bill of Materials table */
.bom-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1rem;
  font-size: 0.95rem;
}

.bom-table th,
.bom-table td {
  border: 1px solid #ccc;
  padding: 0.6rem;
  text-align: left;
}

.bom-table th {
  background-color: #f0f0f0;
  font-weight: bold;
}

.bom-table tr:nth-child(even) {
  background-color: #fafafa;
}

.image-row {
  display: flex;
  justify-content: center;
  gap: 30px;
  flex-wrap: wrap;
  margin: 30px 0;
}

.image-row figure {
  margin: 0;
  max-width: 45%;
}

.project-image {
  width: 100%;
  max-width: 500px;
  height: auto;
  display: block;
  margin: 0 auto;
}


/* Typography scale */
h1 {
  font-size: 2.4rem;
  margin-bottom: 0.6rem;
}

h2 {
  font-size: 1.8rem;
  margin-top: 2.2rem;
  margin-bottom: 0.6rem;
  border-bottom: 2px solid #ddd;
  padding-bottom: 0.3rem;
}

h3 {
  font-size: 1.3rem;
  margin-top: 1.6rem;
  margin-bottom: 0.4rem;
}

body {
  font-size: 16.5px;
}

h1, h2, h3 {
  font-weight: 600;
}

h1, h2, h3 {
  font-family: "Times New Roman", serif;
}

.code-block {
  background: #f7f7f7;
  border: 1px solid #ddd;
  border-radius: 6px;
  padding: 1rem;
  overflow-x: auto;
  font-family: "Courier New", Courier, monospace;
  font-size: 0.85rem;
  line-height: 1.4;
  margin: 1.5rem 0;
}

ul li {
  margin-bottom: 0.4rem;
}

ul li a {
  color: #0056b3;
  text-decoration: none;
}

ul li a:hover {
  text-decoration: underline;
}

.video-container {
  position: relative;
  padding-bottom: 56.25%; /* 16:9 aspect ratio */
  height: 0;
  overflow: hidden;
  margin: 1.5rem 0;
}

.video-container iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}