:root {
  --color-bg: #ffffff;
  --color-primary: #1a73e8;
  --color-secondary: #4a4a4a;
  --color-muted: #777777;
  --color-border: #e0e0e0;
  --font-sans: "Helvetica Neue", Arial, sans-serif;
  --font-mono: "Courier New", monospace;
  --spacing-unit: 1rem;
  --radius: 4px;
  --bg-image: url("bg.png");
}

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

html {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-secondary);
  background-color: var(--color-bg);
  scroll-behavior: smooth;
  background-image: var(--bg-image);
  background-size: cover;
  background-position: center;
  background-attachment: fixed;
}

body {
  max-width: 960px;
  margin: 0 auto;
  padding: var(--spacing-unit);
  /* background-color: rgba(255, 255, 255, 0.8);
  background-blend-mode: lighten; */
}

nav {
  position: sticky;
  top: 0;
  left: 0;
  width: 100%;
  background-color: white;
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
}

nav ul {
  display: flex;
  justify-content: center;
  list-style: none;
}

nav li + li {
  margin-left: var(--spacing-unit);
}

nav a {
  display: inline-block;
  padding: calc(var(--spacing-unit) / 2) var(--spacing-unit);
  color: var(--color-secondary);
  text-decoration: none;
  font-weight: 500;
  border-radius: var(--radius);
}

nav a:hover,
nav a:focus {
  color: var(--color-bg);
  background-color: var(--color-primary);
}

section {
  margin-bottom: calc(var(--spacing-unit) * 2);
  padding: calc(var(--spacing-unit) * 1.5);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: #fafafa;
}

section h1,
section h2 {
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: var(--spacing-unit);
}

#blog {
  background-color: blueviolet;
}

#blog a {
  color: white;
}

#about {
  margin-top: var(--spacing-unit);
}

#about p {
  margin-bottom: var(--spacing-unit);
}

#about ul {
  list-style: disc inside;
  margin-top: var(--spacing-unit);
}

#about li + li {
  margin-top: calc(var(--spacing-unit) / 2);
}

.skill-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: var(--spacing-unit);
}

.skill {
  padding: var(--spacing-unit);
  background-color: #ffffff;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.skill h2 {
  font-size: 1.125rem;
  margin-bottom: calc(var(--spacing-unit) / 2);
}

.cert-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: var(--spacing-unit);
  justify-items: center;
}

.cert-item {
  position: relative;
  overflow: hidden;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
}

.cert-item img {
  width: 100%;
  height: auto;
  display: block;
  transition: transform 0.3s ease;
}

.cert-item:hover img {
  transform: scale(1.05);
}

.cert-overlay {
  position: absolute;
  bottom: 0;
  width: 100%;
  background: rgba(26, 115, 232, 0.85);
  color: #fff;
  text-align: center;
  padding: calc(var(--spacing-unit) / 2);
  font-size: 0.875rem;
  opacity: 0;
  transition: opacity 0.3s ease;
}

.cert-item:hover .cert-overlay {
  opacity: 1;
}

#message form {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-unit);
  max-width: 600px;
  width: 100%;
  margin: 0 auto;
  padding: var(--spacing-unit);
}

#message label {
  font-weight: 500;
}

#message input,
#message textarea {
  width: 100%;
  padding: calc(var(--spacing-unit) / 2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-family: var(--font-sans);
  font-size: 1rem;
}

#message input {
  height: 40px;
}

#message textarea {
  height: 150px;
  line-height: 1.4;
  resize: vertical;
}

#message button {
  align-self: flex-start;
  padding: calc(var(--spacing-unit) / 2) var(--spacing-unit);
  background-color: var(--color-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 1rem;
  cursor: pointer;
  transition: background-color 0.2s ease;
}

#message button:hover,
#message button:focus {
  background-color: #1669c1;
}

#contact {
  text-align: center;
}

#contact p {
  margin-bottom: var(--spacing-unit);
  font-size: 1rem;
}

#contact a {
  margin: 0 var(--spacing-unit);
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
}

#contact a:hover {
  text-decoration: underline;
}

@media (max-width: 600px) {
  nav ul {
    flex-direction: column;
    align-items: center;
  }

  nav li + li {
    margin-left: 0;
    margin-top: var(--spacing-unit);
  }
}