:root {
  --bg-primary: #f4f6f9;
  --bg-card: #ffffff;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --border-color: #e2e8f0;
  --primary-color: #3b82f6;
  --primary-hover: #2563eb;
  --primary-light: #eff6ff;
  --accent-color: #10b981;
  --input-bg: #f8fafc;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
  --shadow-md: 0 10px 25px -5px rgba(0,0,0,0.08), 0 8px 10px -6px rgba(0,0,0,0.01);
  --radius-lg: 16px;
  --radius-md: 10px;
  --transition: all 0.25s ease;
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-card: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --border-color: #334155;
  --primary-color: #38bdf8;
  --primary-hover: #0284c7;
  --primary-light: #1e3a8a33;
  --accent-color: #34d399;
  --input-bg: #0f172a;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 10px 25px -5px rgba(0,0,0,0.5);
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  transition: var(--transition);
}

.app-container {
  width: 100%;
  max-width: 640px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header-content h1 {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-top: 4px;
}

.theme-toggle-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  padding: 8px 14px;
  border-radius: var(--radius-md);
  cursor: pointer;
  font-weight: 500;
  font-size: 0.875rem;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

.theme-toggle-btn:hover {
  border-color: var(--primary-color);
}

[data-theme="light"] .dark-icon {
  display: inline;
}
[data-theme="light"] .light-icon {
  display: none;
}

[data-theme="dark"] .light-icon {
  display: inline;
}
[data-theme="dark"] .dark-icon {
  display: none;
}

.converter-card {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-color);
  transition: var(--transition);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.category-group {
  margin-bottom: 24px;
}

label {
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
}

.form-control {
  width: 100%;
  padding: 12px 16px;
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: inherit;
  outline: none;
  transition: var(--transition);
}

.form-control:focus {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px var(--primary-light);
}

.conversion-grid {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 16px;
  margin-bottom: 24px;
}

.unit-select {
  margin-top: 8px;
}

.swap-container {
  display: flex;
  align-items: center;
  justify-content: center;
  padding-top: 24px;
}

.swap-btn {
  background-color: var(--primary-light);
  color: var(--primary-color);
  border: 1px solid var(--border-color);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  font-size: 1.25rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.swap-btn:hover {
  background-color: var(--primary-color);
  color: #ffffff;
  transform: rotate(180deg);
}

.result-input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.result-input {
  font-weight: 600;
  padding-right: 44px;
}

.copy-btn {
  position: absolute;
  right: 8px;
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.1rem;
  padding: 6px;
  border-radius: 6px;
  transition: var(--transition);
  color: var(--text-secondary);
}

.copy-btn:hover {
  background-color: var(--border-color);
}

.formula-display {
  background-color: var(--primary-light);
  border-left: 4px solid var(--primary-color);
  padding: 12px 16px;
  border-radius: 6px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-primary);
  margin-bottom: 20px;
}

.calculation-steps-container {
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 16px 20px;
}

.calculation-steps-container h3 {
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  margin-bottom: 10px;
}

.steps-list {
  padding-left: 20px;
  font-size: 0.9rem;
  color: var(--text-primary);
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.steps-list li {
  line-height: 1.4;
}

.app-footer {
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

@media (max-width: 580px) {
  .conversion-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .swap-container {
    padding-top: 0;
    margin: 4px 0;
  }

  .swap-btn:hover {
    transform: rotate(90deg);
  }
}