* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: #0a0f1f;
  color: #d0e1f9;
  line-height: 1.6;
  padding: 1rem;
  min-height: 100vh;
}

nav {
  display: flex;
  justify-content: center;
  background-color: #101d42;
  padding: 0.75rem;
  flex-wrap: wrap;
  box-shadow: 0 2px 5px rgba(0,0,0,0.5);
}

nav a {
  color: #a3cef1;
  margin: 0 1rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 1.1rem;
  transition: color 0.2s ease;
}

nav a:hover {
  color: #58a4b0;
  text-decoration: underline;
}

main {
  max-width: 900px;
  margin: auto;
  padding: 1rem;
}

.page {
  display: none;
}

.page.active {
  display: block;
}

.container {
  text-align: center;
}

.profile-image {
  max-width: 150px;
  border-radius: 50%;
  margin: 1rem 0;
  border: 3px solid #58a4b0;
}

.portfolio-heading {
  font-size: 2rem;
  margin-top: 1rem;
  color: #a3cef1;
}

.about-me {
  margin-top: 1rem;
  margin-bottom: 1.5rem;
  font-size: 1.05rem;
  color: #d0e1f9;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
  text-align: left;
}

.button {
  display: inline-block;
  padding: 0.6rem 1.2rem;
  margin: 0.5rem 0.3rem;
  background-color: #1e88e5;
  color: #ffffff;
  text-decoration: none;
  border-radius: 6px;
  font-weight: 600;
  font-size: 1rem;
  border: none;
  cursor: pointer;
  transition: background-color 0.3s ease;
  user-select: none;
}

.button:hover,
.button:focus {
  background-color: #1565c0;
  outline: none;
}

.window {
  background-color: #192336;
  border: 1px solid #2c3e50;
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin: 1rem 0;
  color: #cfd8dc;
  text-align: left;
}

.subsection h3 {
  margin-top: 2rem;
  color: #a3cef1;
}

.tag-container {
  margin: 1rem 0;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

.tag-container button {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: 20px;
  background-color: #2a3b5f;
  color: #a3cef1;
  cursor: pointer;
  transition: background-color 0.3s ease;
  font-weight: 600;
  user-select: none;
}

.tag-container button.active {
  background-color: #1e88e5;
  color: #ffffff;
}

.tag-container button:hover:not(.active),
.tag-container button:focus:not(.active) {
  background-color: #3d5a80;
  outline: none;
}

.github-link {
  background-color: #0d47a1;
  color: white;
  margin-top: 0.5rem;
  display: inline-block;
}

.github-link:hover,
.github-link:focus {
  background-color: #002171;
  outline: none;
}

@media (max-width: 600px) {
  nav a {
    margin: 0.4rem 0.5rem;
    font-size: 1rem;
  }

  .button {
    font-size: 0.9rem;
  }
}