:root {
  --bg-primary: #ffffff;
  --bg-secondary: #f5f5f5;
  --text-primary: #1a1a1a;
  --text-secondary: #666666;
  --border-color: #e0e0e0;
  --accent-color: #0066cc;
  --accent-hover: #0052a3;
}

html[data-theme="dark"] {
  --bg-primary: #1a1a1a;
  --bg-secondary: #2d2d2d;
  --text-primary: #ffffff;
  --text-secondary: #b0b0b0;
  --border-color: #404040;
  --accent-color: #4da6ff;
  --accent-hover: #66b3ff;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: 'Inter', sans-serif;
  color: var(--text-primary);
  background: var(--bg-primary);
  line-height: 1.6;
  transition: background-color 0.3s ease, color 0.3s ease;
}

a {
  color: inherit;
  text-decoration: none;
}

.container {
  width: min(1120px, calc(100% - 2rem));
  margin: 0 auto;
}

/* Header & Navigation */
.site-header {
  background: var(--bg-primary);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

.nav-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 0;
}

.brand {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--text-primary);
  transition: color 0.2s ease;
}

.brand:hover {
  color: var(--accent-color);
}

.site-nav {
  display: flex;
  gap: 2rem;
  align-items: center;
  flex-wrap: wrap;
}

.site-nav a {
  color: var(--text-primary);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s ease;
}

.site-nav a:hover,
.site-nav a.active {
  color: var(--accent-color);
}

/* Theme Toggle Button */
.theme-toggle {
  background: none;
  border: 1px solid var(--border-color);
  cursor: pointer;
  font-size: 1.25rem;
  padding: 0.5rem;
  border-radius: 6px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.2s ease, border-color 0.2s ease;
}

.theme-toggle:hover {
  background-color: var(--bg-secondary);
  border-color: var(--accent-color);
}

.theme-icon {
  display: inline-block;
  transition: transform 0.3s ease;
}

.hero {
  padding: 5rem 0 4rem;
}

.hero-content,
.split-layout,
.contact-layout {
  display: grid;
  gap: 2rem;
  align-items: center;
}

.hero-content {
  grid-template-columns: 1.2fr 0.8fr;
}

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.24em;
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent-color);
  margin-bottom: 0.75rem;
}

h1,
h2,
h3 {
  line-height: 1.2;
  margin-top: 0;
  color: var(--text-primary);
}

h1 {
  font-size: clamp(2rem, 4vw, 3rem);
  margin-bottom: 1rem;
}

h2 {
  font-size: 2rem;
  margin-bottom: 1rem;
}

h3 {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

p {
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

.lead {
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 640px;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-top: 1.5rem;
}

.btn {
  display: inline-block;
  padding: 0.8rem 1.15rem;
  border-radius: 999px;
  font-weight: 600;
  transition: transform 0.2s ease, background 0.2s ease;
  border: none;
  cursor: pointer;
  text-decoration: none;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn-primary {
  background: var(--accent-color);
  color: #fff;
}

.btn-primary:hover {
  background: var(--accent-hover);
}

.btn-secondary {
  background: var(--bg-primary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background: var(--bg-secondary);
}

.hero-card,
.info-panel,
.contact-form,
.card {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 1rem;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
  transition: background-color 0.3s ease, border-color 0.3s ease, box-shadow 0.2s ease;
}

html[data-theme="dark"] .hero-card:hover,
html[data-theme="dark"] .info-panel:hover,
html[data-theme="dark"] .card:hover {
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

.hero-card,
.info-panel {
  padding: 1.5rem;
}

.section {
  padding: 2rem 0 4rem;
  border-bottom: 1px solid var(--border-color);
}

.section:last-of-type {
  border-bottom: none;
}

.section-heading {
  margin-bottom: 1.5rem;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1.25rem;
}

.card {
  padding: 1.5rem;
}

.card h3 {
  color: var(--text-primary);
}

.card p {
  color: var(--text-secondary);
}

/* Project Filters */
.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 2rem 0 2rem 0;
  padding-bottom: 1rem;
}

.filter-btn {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
  padding: 0.5rem 1rem;
  border-radius: 6px;
  cursor: pointer;
  font-weight: 500;
  font-size: 0.95rem;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.filter-btn:hover {
  border-color: var(--accent-color);
  background-color: var(--bg-primary);
}

.filter-btn.active {
  background-color: var(--accent-color);
  color: white;
  border-color: var(--accent-color);
}

.filter-btn:focus {
  outline: 2px solid var(--accent-color);
  outline-offset: 2px;
}

/* Project Cards */
.project-card {
  position: relative;
  transition: opacity 0.3s ease, transform 0.2s ease;
}

.project-card.hidden {
  display: none;
}

.project-category {
  display: inline-block;
  background-color: var(--accent-color);
  color: white;
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  margin-top: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.contact-layout {
  grid-template-columns: 1fr 1fr;
}

.contact-form {
  padding: 1.5rem;
  display: grid;
  gap: 1rem;
}

label {
  display: grid;
  gap: 0.4rem;
  font-weight: 600;
  color: var(--text-primary);
}

input,
textarea {
  width: 100%;
  border: 1px solid var(--border-color);
  border-radius: 0.75rem;
  padding: 0.8rem 0.9rem;
  font: inherit;
  color: var(--text-primary);
  background: var(--bg-primary);
  transition: border-color 0.2s ease, background-color 0.3s ease;
}

input:focus,
textarea:focus {
  outline: 2px solid rgba(0, 102, 204, 0.2);
  border-color: var(--accent-color);
}

/* Form Validation */
.form-wrapper {
  width: 100%;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.error-message {
  display: none;
  color: #d32f2f;
  font-size: 0.85rem;
  font-weight: 500;
  margin-top: -0.2rem;
}

.form-group.has-error .error-message {
  display: block;
}

.form-group.has-error input,
.form-group.has-error textarea {
  border-color: #d32f2f;
  background-color: rgba(211, 47, 47, 0.04);
}

.form-group.has-error input:focus,
.form-group.has-error textarea:focus {
  outline: 2px solid rgba(211, 47, 47, 0.2);
  border-color: #d32f2f;
}

html[data-theme="dark"] .form-group.has-error input,
html[data-theme="dark"] .form-group.has-error textarea {
  border-color: #ff6b6b;
  background-color: rgba(255, 107, 107, 0.08);
}

html[data-theme="dark"] .form-group.has-error input:focus,
html[data-theme="dark"] .form-group.has-error textarea:focus {
  outline: 2px solid rgba(255, 107, 107, 0.2);
  border-color: #ff6b6b;
}

html[data-theme="dark"] .error-message {
  color: #ff6b6b;
}

.success-message {
  background-color: #4caf50;
  color: white;
  padding: 1rem 1.25rem;
  border-radius: 0.75rem;
  margin-bottom: 1.5rem;
  font-weight: 500;
  box-shadow: 0 2px 8px rgba(76, 175, 80, 0.3);
  animation: slideDown 0.3s ease;
}

html[data-theme="dark"] .success-message {
  background-color: #45a049;
  box-shadow: 0 2px 8px rgba(69, 160, 73, 0.4);
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.site-footer {
  border-top: 1px solid var(--border-color);
  padding: 1.5rem 0 2rem;
  color: var(--text-secondary);
  background-color: var(--bg-secondary);
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

.footer-content p {
  margin: 0.5rem 0;
}

@media (max-width: 760px) {
  .hero-content,
  .split-layout,
  .contact-layout,
  .card-grid {
    grid-template-columns: 1fr;
  }

  .nav-bar {
    flex-direction: column;
    gap: 0.75rem;
  }

  .site-nav {
    flex-wrap: wrap;
    justify-content: center;
    gap: 1rem;
  }

  .hero {
    padding-top: 3rem;
  }

  h1 {
    font-size: 1.75rem;
  }

  h2 {
    font-size: 1.5rem;
  }

  .footer-content {
    flex-direction: column;
    text-align: center;
  }

  /* Mobile Filters */
  .filters {
    gap: 0.5rem;
    margin: 1.5rem 0;
  }

  .filter-btn {
    flex: 1 1 auto;
    min-width: 80px;
    font-size: 0.85rem;
    padding: 0.45rem 0.75rem;
  }
}