* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.6;
  color: #e8edf3;
  background: #0d1117;
}

img {
  display: block;
  max-width: 100%;
}

.container {
  width: min(1100px, 92%);
  margin: 0 auto;
}

/* Header */

.site-header {
  padding: 70px 0 45px;
  text-align: center;
  background: #161b22;
  border-bottom: 1px solid #30363d;
}

.eyebrow {
  margin: 0 0 8px;
  font-size: 0.9rem;
  font-weight: bold;
  letter-spacing: 0.12rem;
  text-transform: uppercase;
  color: #58a6ff;
}

h1 {
  margin: 0;
  font-size: clamp(2.5rem, 7vw, 4.5rem);
}

.intro {
  max-width: 760px;
  margin: 18px auto 30px;
  color: #b8c1cc;
}

/* Navigation buttons */

.site-header nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 14px;
  margin-top: 24px;
}

.site-header nav a {
  display: inline-block;
  min-width: 135px;
  padding: 13px 22px;
  font-size: 1rem;
  font-weight: 700;
  text-align: center;
  color: #e8edf3;
  text-decoration: none;
  background: #0d1117;
  border: 1px solid #30363d;
  border-radius: 8px;
}

.site-header nav a:hover,
.site-header nav a:focus-visible {
  color: #ffffff;
  border-color: #58a6ff;
}

/* Main sections */

main {
  padding: 30px 0 65px;
}

section {
  margin: 28px 0;
  padding: 30px;
  background: #161b22;
  border: 1px solid #30363d;
  border-radius: 14px;
}

h2 {
  margin-top: 0;
  padding-bottom: 10px;
  border-bottom: 1px solid #30363d;
}

h3 {
  margin-top: 0;
}

p {
  color: #c5ced8;
}

.workflow {
  padding: 14px;
  background: #0d1117;
  border-left: 4px solid #58a6ff;
}

/* Certificates */

.cert-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
  align-items: stretch;
}

.certificate-card {
  overflow: hidden;
  display: flex;
  flex-direction: column;
  text-align: center;
  background: #0d1117;
  border: 1px solid #30363d;
  border-radius: 12px;
}

.certificate-image-link {
  display: block;
  background: #ffffff;
}

.certificate-card img {
  width: 100%;
  height: auto;
  margin: 0 auto;
  background: #ffffff;
  border-bottom: 1px solid #30363d;
}

.certificate-content {
  display: flex;
  flex: 1;
  flex-direction: column;
  align-items: center;
  padding: 20px;
}

.certificate-content h3 {
  margin-bottom: 6px;
}

.certificate-content p {
  margin: 0 0 16px;
}

.certificate-content .button {
  margin-top: auto;
}

/* Projects */

.project-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.project-card {
  padding: 22px;
  background: #0d1117;
  border: 1px solid #30363d;
  border-radius: 12px;
}

.project-card p:last-child {
  margin-bottom: 0;
}

/* Green page buttons */

.button {
  display: inline-block;
  margin-top: 10px;
  padding: 12px 20px;
  font-weight: bold;
  color: #ffffff;
  text-decoration: none;
  background: #238636;
  border-radius: 8px;
}

.button:hover,
.button:focus-visible {
  background: #2ea043;
}

/* Footer */

footer {
  padding: 28px 0;
  text-align: center;
  background: #161b22;
  border-top: 1px solid #30363d;
}

footer p {
  margin: 0;
}

/* Mobile layout */

@media (max-width: 750px) {
  .cert-grid,
  .project-grid {
    grid-template-columns: 1fr;
  }

  section {
    padding: 22px;
  }

  .site-header {
    padding-top: 45px;
  }

  .site-header nav a {
    min-width: 145px;
  }
}