/* ============================================
   Nimbus Fitness — Design System
   ============================================ */

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img, picture, video, canvas, svg {
  display: block;
  max-width: 100%;
}

input, button, textarea, select {
  font: inherit;
}

a {
  color: var(--color-primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

ul, ol {
  list-style: none;
}

/* --- Custom Properties (Light) --- */
:root {
  /* Brand */
  --color-primary: #4F46E5;
  --color-primary-light: #818CF8;
  --color-primary-dark: #3730A3;
  --color-accent: #06B6D4;
  --color-accent-light: #67E8F9;

  /* Surfaces */
  --color-bg: #FFFFFF;
  --color-bg-alt: #F8FAFC;
  --color-surface: #F1F5F9;
  --color-surface-hover: #E2E8F0;

  /* Text */
  --color-text: #0F172A;
  --color-text-secondary: #475569;
  --color-text-muted: #94A3B8;

  /* Borders */
  --color-border: #E2E8F0;

  /* Feedback */
  --color-success: #10B981;
  --color-error: #EF4444;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;

  /* Typography */
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;

  /* Layout */
  --max-width: 72rem;
  --max-width-narrow: 42rem;

  /* Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
}

/* --- Dark Mode --- */
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #818CF8;
    --color-primary-light: #A5B4FC;
    --color-primary-dark: #6366F1;
    --color-accent: #22D3EE;
    --color-accent-light: #67E8F9;

    --color-bg: #0F172A;
    --color-bg-alt: #1E293B;
    --color-surface: #1E293B;
    --color-surface-hover: #334155;

    --color-text: #F1F5F9;
    --color-text-secondary: #CBD5E1;
    --color-text-muted: #64748B;

    --color-border: #334155;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  }
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  line-height: 1.2;
  font-weight: 700;
  color: var(--color-text);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-2xl); }
h4 { font-size: var(--font-size-xl); }

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

/* --- Utilities --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-lg);
}

.container--narrow {
  max-width: var(--max-width-narrow);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 0.75rem 1.5rem;
  font-size: var(--font-size-base);
  font-weight: 600;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: background-color var(--transition-fast), transform var(--transition-fast);
  text-decoration: none;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

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

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

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

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

/* --- Forms --- */
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
}

.form-label {
  font-size: var(--font-size-sm);
  font-weight: 600;
  color: var(--color-text);
}

.form-input,
.form-textarea {
  padding: 0.75rem 1rem;
  font-size: var(--font-size-base);
  color: var(--color-text);
  background-color: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  transition: border-color var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.15);
}

.form-textarea {
  resize: vertical;
  min-height: 8rem;
}

/* --- Section spacing --- */
.section {
  padding-block: var(--space-4xl);
}

/* --- Responsive --- */
@media (max-width: 768px) {
  h1 { font-size: var(--font-size-3xl); }
  h2 { font-size: var(--font-size-2xl); }
  h3 { font-size: var(--font-size-xl); }

  .section {
    padding-block: var(--space-3xl);
  }
}

@media (min-width: 1024px) {
  h1 { font-size: var(--font-size-5xl); }
}