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

:root {
  /* Dark theme (default) */
  --bg-primary: #111;
  --bg-secondary: #1a1a1a;
  --bg-tertiary: #222;
  --bg-overlay: rgba(0, 0, 0, 0.9);
  --text-primary: #e5e5e5;
  --text-secondary: #999;
  --text-tertiary: #888;
  --text-quaternary: #666;
  --text-heading: #fff;
  --text-link: #ccc;
  --text-link-hover: #fff;
  --border-primary: #333;
  --border-secondary: #444;
  --btn-primary-bg: #fff;
  --btn-primary-text: #111;
  --btn-primary-hover: #e5e5e5;
  --btn-secondary-bg: #222;
  --btn-secondary-border: #333;
  --btn-secondary-hover-bg: #2a2a2a;
  --btn-disabled-bg: #333;
  --btn-disabled-text: #666;
  --btn-selected-bg: #fff;
  --btn-selected-text: #111;
  --card-bg: #1a1a1a;
  --card-border: #333;
}

@media (prefers-color-scheme: light) {
  :root {
    /* Light theme */
    --bg-primary: #fafafa;
    --bg-secondary: #fff;
    --bg-tertiary: #f5f5f5;
    --bg-overlay: rgba(255, 255, 255, 0.95);
    --text-primary: #1a1a1a;
    --text-secondary: #666;
    --text-tertiary: #666;
    --text-quaternary: #999;
    --text-heading: #000;
    --text-link: #333;
    --text-link-hover: #000;
    --border-primary: #e0e0e0;
    --border-secondary: #d0d0d0;
    --btn-primary-bg: #000;
    --btn-primary-text: #fff;
    --btn-primary-hover: #333;
    --btn-secondary-bg: #fff;
    --btn-secondary-border: #e0e0e0;
    --btn-secondary-hover-bg: #f5f5f5;
    --btn-disabled-bg: #e0e0e0;
    --btn-disabled-text: #999;
    --btn-selected-bg: #000;
    --btn-selected-text: #fff;
    --card-bg: #fff;
    --card-border: #e0e0e0;
  }
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  padding: 16px;
  padding-bottom: 100px;
}

h1 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-heading);
}

.subtitle {
  font-size: 0.85rem;
  color: var(--text-tertiary);
  margin-bottom: 24px;
}

.subtitle a, .subtitle a:visited {
  color: var(--text-link);
  text-decoration: none;
  transition: all 0.15s ease;
}
.subtitle a:hover {
  text-decoration: none;
  color: var(--text-link-hover);
}

.substances-container {
  display: flex;
  flex-direction: column;
}

.substance-section {
  margin-bottom: 0;
}

.section-title {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-quaternary);
  margin-bottom: 12px;
  margin-top: 24px;
}

.substance-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 8px;
}

.substance-btn {
  background: var(--btn-secondary-bg);
  border: 1px solid var(--btn-secondary-border);
  color: var(--text-link);
  padding: 12px 8px;
  border-radius: 8px;
  font-size: 0.875rem;
  cursor: pointer;
  transition: all 0.15s ease;
  text-align: center;
}

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

.substance-btn.selected {
  background: var(--btn-selected-bg);
  color: var(--btn-selected-text);
  border-color: var(--btn-selected-bg);
  font-weight: 500;
}

.check-btn {
  position: fixed;
  bottom: 16px;
  left: 16px;
  right: 16px;
  background: var(--btn-primary-bg);
  color: var(--btn-primary-text);
  border: none;
  padding: 16px;
  border-radius: 12px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}

.check-btn:disabled {
  background: var(--btn-disabled-bg);
  color: var(--btn-disabled-text);
  cursor: not-allowed;
}

.check-btn:not(:disabled):hover {
  background: var(--btn-primary-hover);
}

.results-overlay {
  position: fixed;
  inset: 0;
  background: var(--bg-overlay);
  display: none;
  flex-direction: column;
  z-index: 100;
  overflow-y: auto;
}

.results-overlay.visible {
  display: flex;
}

.results-header {
  border-bottom: 1px solid var(--border-primary);
  position: sticky;
  top: 0;
  background: var(--bg-primary);
}

.results-header-inner {
  padding: 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.results-title {
  font-size: 1.25rem;
  font-weight: 600;
}

.close-btn {
  background: var(--btn-secondary-bg);
  color: var(--text-secondary);
  padding: 8px 12px;
  border-radius: 8px;
  font-size: 1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--btn-secondary-border);
}
.close-btn:hover {
  background: var(--btn-secondary-hover-bg);
  color: var(--text-heading);
  border-color: var(--border-secondary);
}

.results-content {
  padding: 16px;
  flex: 1;
}

/* Desktop: constrain results overlay content width */
@media (min-width: 1024px) {
  .results-header-inner {
    max-width: 50vw;
    margin: 0 auto;
    width: 100%;
  }

  .results-content {
    max-width: 50vw;
    margin: 0 auto;
    width: 100%;
  }
}

.interaction-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 12px;
}

.interaction-substances {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 8px;
}

.interaction-level {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  margin-bottom: 8px;
}

.level-synergy { background: #166534; color: #bbf7d0; }
.level-no-synergy { background: #1e3a5f; color: #bfdbfe; }
.level-decrease { background: #1e40af; color: #bfdbfe; }
.level-caution { background: #854d0e; color: #fef08a; }
.level-unsafe { background: #9a3412; color: #fed7aa; }
.level-dangerous { background: #991b1b; color: #fecaca; }

.interaction-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

.selected-count {
  background: var(--bg-tertiary);
  color: var(--text-heading);
  padding: 2px 8px;
  border-radius: 12px;
  font-size: 0.75rem;
  margin-left: 8px;
}

.disclaimer {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 12px;
  margin-top: 16px;
  font-size: 0.75rem;
  color: var(--text-tertiary);
  line-height: 1.5;
}

.no-interactions {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-quaternary);
}

/* Desktop breakpoint */
@media (min-width: 1024px) {
  body {
    padding: 24px;
    padding-bottom: 100px;
    max-width: 1400px;
    margin: 0 auto;
  }

  .substances-container {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
    align-items: start;
  }

  .substance-section {
    margin-bottom: 0;
  }

  .substance-section .section-title {
    margin-top: 0;
  }

  .substance-section:first-child .section-title {
    margin-top: 0;
  }
}