:root {
  --primary: #1976d2;
  --primary-light: #63a4ff;
  --secondary: #ff9800;
  --accent-teal: #00897b;
  --accent-purple: #7b1fa2;
  --accent-pink: #c2185b;
  --surface: #fafbfc;
  --background: #f3f6f8;
  --on-primary: #ffffff;
  --on-surface: #000000;
  --on-background: #000000;
  --success: #2e7d32;
  --duration-highlight: #00897b;
  --duration-bg: #e0f2f1;
  --instruction-accent: #d32f2f;
  --error: #d32f2f;
  --warning: #ffa000;
  --info: #0288d1;
  --shadow: 0 2px 4px rgba(0,0,0,0.1), 0 4px 8px rgba(0,0,0,0.1);
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --font-size: 16px;
  --border-radius: 12px;
}

.dark-mode {
  --primary: #2196f3;
  --primary-light: #6ec6ff;
  --secondary: #ffb74d;
  --accent-teal: #4db6ac;
  --accent-purple: #ba68c8;
  --accent-pink: #f06292;
  --surface: #1e1e1e;
  --background: #121212;
  --on-primary: #ffffff;
  --on-surface: #ffffff;
  --on-background: #ffffff;
  --success: #4caf50;
  --duration-highlight: #4db6ac;
  --duration-bg: rgba(77, 182, 172, 0.15);
  --instruction-accent: #f44336;
  --error: #f44336;
  --warning: #ffb300;
  --info: #29b6f6;
  --shadow: 0 2px 4px rgba(0,0,0,0.3), 0 4px 8px rgba(0,0,0,0.3);
}

html, body {
  font-family: 'Roboto Mono', monospace;
  background-color: var(--background);
  color: var(--on-background);
  transition: var(--transition);
  font-size: var(--font-size);
  line-height: 1.6;
  margin: 0;
  padding: 0;
  min-height: 100vh;
}

/* Skip to main content link for accessibility */
.skip-link {
  position: absolute;
  top: -40px;
  left: 6px;
  background: var(--primary);
  color: white;
  padding: 8px;
  text-decoration: none;
  border-radius: 4px;
  z-index: 10000;
}

.skip-link:focus {
  top: 6px;
}

.brand-header {
  background: var(--surface);
  color: var(--on-background);
  padding: 2rem 0 0;
  margin-bottom: 1rem;
  text-align: center;
  border-bottom: none;
}

.brand-header .section-title {
  margin-bottom: 0;
  padding-bottom: 0.5rem;
}

.brand-title {
  font-size: calc(var(--font-size) * 1.8);
  font-weight: 700;
  margin: 0;
}

.brand-subtitle {
  font-size: calc(var(--font-size) * 0.9);
  font-weight: 300;
  margin: 0.5rem 0 0;
  opacity: 0.8;
}

.location-subtitle {
  font-size: calc(var(--font-size) * 0.8);
  font-weight: 400;
  margin: 0.25rem 0 0;
  opacity: 0.7;
  color: var(--primary);
}

.datetime-display {
  position: fixed;
  top: 1rem;
  left: 1rem;
  background: var(--surface);
  color: var(--on-surface);
  /* slightly taller pill for clearer vertical centering */
  padding: 1rem 1.75rem;
  min-height: 56px;
  border-radius: 50px;
  box-shadow: var(--shadow);
  font-weight: 500;
  z-index: 1000;
  font-size: calc(var(--font-size) * 0.85);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center; /* vertically center child lines */
  text-align: center; /* center text fallback */
}

.date-part {
  margin-bottom: 0.25rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.date-main {
  line-height: 1;
}

.date-year {
  display: block;
  margin-top: 0.35rem;
  font-weight: 600;
  font-size: calc(var(--font-size) * 0.85);
  transform: translateY(0.12rem); /* small nudge to visually drop the year */
}

.time-part {
  font-size: calc(var(--font-size) * 0.8);
  opacity: 0.8;
}

.date-main, .date-year, .time-part {
  text-align: center;
}

.controls-container {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  align-items: center; /* center top-right controls under the dark mode button */
}

.control-btn {
  background: var(--surface);
  color: var(--on-surface);
  border: none;
  border-radius: 50px;
  padding: 0.75rem 1.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: var(--shadow);
  transition: var(--transition);
  font-weight: 500;
  font-size: calc(var(--font-size) * 0.9);
  text-decoration: none;
}

.control-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 12px rgba(0,0,0,0.15);
}

.control-btn:focus {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.home-btn {
  background: var(--primary);
  color: var(--on-primary);
}

.main-content {
  padding: 1rem 2rem 2rem;
  max-width: 1400px;
  margin: 0 auto;
}

.page-title {
  font-size: calc(var(--font-size) * 1.8);
  font-weight: 700;
  margin-bottom: 2rem;
  color: var(--primary);
  text-align: center;
  position: relative;
}

.page-title::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  width: 100px;
  height: 4px;
  background: var(--secondary);
  border-radius: 2px;
}

.instructions-section {
  margin-bottom: 2rem;
  max-width: 100%;
  text-align: left;
  background: var(--surface);
  padding: 1.5rem;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  border-left: 5px solid var(--instruction-accent);
}

.instructions-title {
  font-size: calc(var(--font-size) * 1.4);
  font-weight: 600;
  color: var(--instruction-accent);
  margin-bottom: 1.5rem;
  display: flex;
  align-items: center;
  gap: 1rem;
}

.instructions-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.instruction-item {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  margin-bottom: 1.5rem;
  padding: 0;
}

.instruction-icon {
  color: var(--success);
  flex-shrink: 0;
  margin-top: 0.2rem;
}

.instruction-text {
  flex: 1;
  color: var(--on-background);
  text-align: left;
}

.categories-container {
  margin-bottom: 2rem;
  max-width: 100%;
}

.section-title {
  font-size: calc(var(--font-size) * 1.4);
  font-weight: 600;
  color: var(--primary);
  margin-bottom: 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--primary-light);
  text-align: center;
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
  justify-items: start;
}

.category-card {
  background: var(--surface);
  overflow: hidden;
  transition: var(--transition);
  width: 100%;
  max-width: 400px;
  height: fit-content;
}

.category-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.category-header {
  color: white;
  padding: 0.4rem 0.5rem;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 0.5rem;
}

/* Make header icon and title larger */
.category-header .category-icon {
  font-size: 32px;
  line-height: 1;
}

.category-card:nth-child(2) .category-header {
  background-color: #388e3c !important;
}

.category-card:nth-child(3) .category-header {
  background-color: #d81b60 !important;
}

.category-card:nth-child(4) .category-header {
  background-color: #7b1fa2 !important;
}

.category-title {
  font-size: 1.3rem;
  font-weight: 600;
  margin: 0;
}

.category-body {
  padding: 1rem 1.5rem;
  display: flex;
  flex-direction: column;
  min-height: auto;
}

.test-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 0;
  transition: var(--transition);
}



.test-item:focus-within {
  background: rgba(0,0,0,0.02);
  border-radius: 8px;
  padding-left: 0.5rem;
  padding-right: 0.5rem;
}

.dark-mode .test-item:focus-within {
  background: rgba(255,255,255,0.02);
}

.test-info {
  flex: 1;
  margin-right: 1rem;
}

.test-name {
  font-weight: 500;
  margin-bottom: 0.25rem;
  color: var(--on-surface);
}

.test-details {
  font-size: 0.9rem;
  color: var(--on-surface);
  opacity: 0.7;
  margin-bottom: 0.5rem;
}

.test-duration {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  background-color: var(--duration-bg);
  color: var(--duration-highlight);
  padding: 0.3rem 0.7rem;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 600;
  margin-top: 0.3rem;
}

.dropdown-container {
  margin-top: 1rem;
  border: 1px solid rgba(0,0,0,0.1);
  border-radius: 8px;
  overflow: hidden;
}

.dark-mode .dropdown-container {
  border-color: rgba(255,255,255,0.1);
}

.dropdown-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1rem;
  background: var(--background);
  border: none;
  width: 100%;
  text-align: left;
  cursor: pointer;
  transition: var(--transition);
}

.dark-mode .dropdown-header {
  background: rgba(255,255,255,0.05);
}

.dropdown-header:hover {
  background: rgba(0,0,0,0.05);
}

.dark-mode .dropdown-header:hover {
  background: rgba(255,255,255,0.1);
}

.dropdown-header:focus {
  outline: 2px solid var(--primary);
  outline-offset: -2px;
}

.dropdown-title {
  font-weight: 500;
  color: var(--on-surface);
  margin: 0;
  font-size: 1rem;
}

.dropdown-icon {
  transition: transform 0.3s ease;
}

.dropdown-icon.rotated {
  transform: rotate(180deg);
}

.dropdown-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out, opacity 0.2s ease;
  opacity: 0;
  background: var(--surface);
}

.dropdown-content.show {
  max-height: 1000px;
  opacity: 1;
  transition: max-height 0.5s ease-in, opacity 0.3s ease;
}

.dropdown-content .test-item {
  margin: 0;
  border-radius: 0;
}


.btn-success {
  background: var(--primary);
  border: none;
  border-radius: 50px;
  padding: 0.35rem 1rem;
  font-weight: 500;
  transition: var(--transition);
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
  color: white;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  cursor: pointer;
  font-family: inherit;
  font-size: 0.8rem;
}

.btn-success:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.2);
  color: white;
}

.btn-success:focus {
  outline: 2px solid white;
  outline-offset: 2px;
}

.empty-space {
  height: 40px;
  visibility: hidden;
}

.footer {
  text-align: center;
  padding: 2rem 0;
  margin-top: 3rem;
  border-top: 1px solid rgba(0,0,0,0.1);
  color: var(--on-surface);
  opacity: 0.7;
  max-width: 100%;
}

.dark-mode .footer {
  border-top: 1px solid rgba(255,255,255,0.1);
}

.footer a {
  color: var(--primary);
  text-decoration: none;
  font-weight: 500;
}

.footer a:hover {
  text-decoration: underline;
}

/* Improved responsive design */
@media (max-width: 768px) {
  .datetime-display, .controls-container {
    position: static;
    margin-bottom: 1rem;
  }
  
  .datetime-display {
    flex-direction: row;
    gap: 1rem;
    justify-content: center;
    margin: 1rem auto;
    width: fit-content;
  }
  
  .date-part {
    margin-bottom: 0;
  }
  
  .controls-container {
    justify-content: center;
    flex-direction: row;
    flex-wrap: wrap;
    position: static;
    margin: 1rem auto;
  }
  
  .main-content {
    padding: 1rem;
  }
  
  .page-title, .brand-title {
    font-size: 1.6rem;
  }
  
  .category-grid {
    grid-template-columns: 1fr;
    justify-items: center;
  }
  
  .category-card {
    max-width: 100%;
  }
  
  .test-item {
    flex-direction: column;
    align-items: flex-start;
    gap: 1rem;
  }
  
  .btn-success {
    align-self: stretch;
    justify-content: center;
  }
}

@media (max-width: 480px) {
  :root {
    --font-size: 14px;
  }
  
  .brand-header {
    padding: 1.5rem 0 0.5rem 0;
  }
  
  .category-body {
    padding: 1rem;
    min-height: 150px;
  }
  
  .instructions-section {
    padding: 1rem;
  }
  
  .instruction-item {
    flex-direction: column;
    gap: 0.5rem;
    text-align: center;
  }
  
  .instruction-icon {
    margin-top: 0;
  }
}