* {
  box-sizing: border-box;
}
body {
  font-family: Arial, sans-serif;
  margin: 0;
  background-color: lightgray;
  color: black;
}
header {
  background-color: black;
  color: white;
  padding: 20px;
}
nav h1 {
  margin: 0;
}
nav ul {
  list-style: none;
  padding: 0;
}
nav li {
  display: inline;
  margin-right: 15px;
}
nav a {
  color: white;
  text-decoration: none;
}
nav a:hover {
  text-decoration: underline;
}
.intro {
  text-align: center;
  padding: 40px 20px;
  background-color: gray;
  color: white;
}
.intro a {
  color: white;
  font-weight: bold;
}
.section {
  background-color: white;
  margin: 30px auto;
  padding: 20px;
  max-width: 900px;
}
.section a {
  color: black;
  font-weight: bold;
}
.project-grid,
.certification-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 15px;
}
.project-card,
.certification-card {
  background-color: white;
  border: 1px solid gray;
  padding: 15px;
}
.project-card img,
.project-image {
  width: 100%;
  max-height: 300px;
  object-fit: cover;
}
.contact {
  text-align: center;
}
footer {
  background-color: black;
  color: white;
  text-align: center;
  padding: 15px;
}
@media screen and (max-width: 768px) {
  nav li {
    display: block;
    margin: 10px 0;
  }

  .project-grid,
  .certification-grid {
    grid-template-columns: 1fr;
  }
}