/* ============================================================
   main.css — ConvertStack Design System
   Variables, Reset, Layout, Typography, Buttons
   ============================================================ */

/* ----------------------------------------------------------
   Custom Properties
   ---------------------------------------------------------- */
:root {
  /* Brand */
  --color-primary:       #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-primary-light: #dbeafe;
  --color-accent:        #f59e0b;
  --color-accent-hover:  #d97706;

  /* Neutrals */
  --color-bg:            #ffffff;
  --color-surface:       #f8fafc;
  --color-border:        #e2e8f0;
  --color-border-strong: #cbd5e1;
  --color-text:          #0f172a;
  --color-text-muted:    #64748b;
  --color-text-subtle:   #94a3b8;

  /* Feedback */
  --color-success:       #16a34a;
  --color-success-light: #dcfce7;
  --color-error:         #dc2626;
  --color-error-light:   #fee2e2;
  --color-warning:       #d97706;
  --color-warning-light: #fef3c7;

  /* Spacing (4px base) */
  --space-1:  4px;
  --space-2:  8px;
  --space-3:  12px;
  --space-4:  16px;
  --space-5:  20px;
  --space-6:  24px;
  --space-8:  32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto,
               'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;

  --text-xs:   0.75rem;   /* 12px */
  --text-sm:   0.875rem;  /* 14px */
  --text-base: 1rem;      /* 16px */
  --text-lg:   1.125rem;  /* 18px */
  --text-xl:   1.25rem;   /* 20px */
  --text-2xl:  1.5rem;    /* 24px */
  --text-3xl:  1.875rem;  /* 30px */
  --text-4xl:  2.25rem;   /* 36px */
  --text-5xl:  3rem;      /* 48px */

  --weight-normal:    400;
  --weight-medium:    500;
  --weight-semibold:  600;
  --weight-bold:      700;

  --leading-tight:  1.25;
  --leading-snug:   1.375;
  --leading-normal: 1.5;
  --leading-relaxed:1.625;

  /* Borders & Radius */
  --radius-sm:  4px;
  --radius-md:  8px;
  --radius-lg:  12px;
  --radius-xl:  16px;
  --radius-2xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm:  0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md:  0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg:  0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl:  0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

  /* Transitions */
  --transition-fast:   150ms ease;
  --transition-normal: 200ms ease;
  --transition-slow:   300ms ease;

  /* Layout */
  --max-width:       1100px;
  --max-width-prose: 720px;
  --header-height:   64px;
}

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

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

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

p, h1, h2, h3, h4, h5, h6 {
  overflow-wrap: break-word;
}

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

a:hover {
  text-decoration: underline;
}

ul, ol {
  list-style: none;
}

/* ----------------------------------------------------------
   Layout
   ---------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-6);
}

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

/* ----------------------------------------------------------
   Site Header
   ---------------------------------------------------------- */
.site-header {
  height: var(--header-height);
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 100;
}

.site-header__inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-header__logo {
  font-size: var(--text-xl);
  font-weight: var(--weight-bold);
  color: var(--color-text);
  letter-spacing: -0.025em;
  text-decoration: none;
}

.site-header__logo span {
  color: var(--color-primary);
}

.site-header__nav {
  display: flex;
  align-items: center;
  gap: var(--space-4);
}

.site-header__nav a:not(.btn) {
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.site-header__nav a:not(.btn):hover {
  color: var(--color-text);
}

/* ----------------------------------------------------------
   Site Footer
   ---------------------------------------------------------- */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding-block: var(--space-8);
  margin-top: var(--space-16);
}

.site-footer__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-4);
}

.site-footer__copy {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}

.site-footer__links {
  display: flex;
  gap: var(--space-6);
}

.site-footer__links a {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.site-footer__links a:hover {
  color: var(--color-text);
}

/* ----------------------------------------------------------
   Typography Utilities
   ---------------------------------------------------------- */
.text-xs     { font-size: var(--text-xs); }
.text-sm     { font-size: var(--text-sm); }
.text-base   { font-size: var(--text-base); }
.text-lg     { font-size: var(--text-lg); }
.text-xl     { font-size: var(--text-xl); }
.text-2xl    { font-size: var(--text-2xl); }
.text-3xl    { font-size: var(--text-3xl); }
.text-4xl    { font-size: var(--text-4xl); }

.font-medium   { font-weight: var(--weight-medium); }
.font-semibold { font-weight: var(--weight-semibold); }
.font-bold     { font-weight: var(--weight-bold); }

.text-muted  { color: var(--color-text-muted); }
.text-subtle { color: var(--color-text-subtle); }
.text-primary{ color: var(--color-primary); }

/* ----------------------------------------------------------
   Buttons
   ---------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  line-height: 1;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color var(--transition-fast),
              border-color var(--transition-fast),
              color var(--transition-fast),
              box-shadow var(--transition-fast),
              opacity var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
  user-select: none;
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
  pointer-events: none;
}

/* Primary */
.btn--primary {
  background: var(--color-primary);
  color: #ffffff;
  border-color: var(--color-primary);
}

.btn--primary:hover {
  background: var(--color-primary-hover);
  border-color: var(--color-primary-hover);
  text-decoration: none;
}

/* Secondary (outline) */
.btn--secondary {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn--secondary:hover {
  background: var(--color-primary-light);
  text-decoration: none;
}

/* Ghost */
.btn--ghost {
  background: transparent;
  color: var(--color-text-muted);
  border-color: transparent;
}

.btn--ghost:hover {
  background: var(--color-surface);
  color: var(--color-text);
  text-decoration: none;
}

/* Upgrade (amber) */
.btn--upgrade {
  background: var(--color-accent);
  color: #ffffff;
  border-color: var(--color-accent);
}

.btn--upgrade:hover {
  background: var(--color-accent-hover);
  border-color: var(--color-accent-hover);
  text-decoration: none;
}

/* Danger */
.btn--danger {
  background: var(--color-error);
  color: #ffffff;
  border-color: var(--color-error);
}

.btn--danger:hover {
  background: #b91c1c;
  border-color: #b91c1c;
  text-decoration: none;
}

/* Sizes */
.btn--sm {
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-xs);
  border-radius: var(--radius-sm);
}

.btn--lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-base);
  border-radius: var(--radius-lg);
}

.btn--xl {
  padding: var(--space-5) var(--space-10);
  font-size: var(--text-lg);
  border-radius: var(--radius-xl);
}

.btn--full {
  width: 100%;
}

/* ----------------------------------------------------------
   Badge / Pill
   ---------------------------------------------------------- */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 2px var(--space-2);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  line-height: 1;
}

.badge--pro {
  background: var(--color-accent);
  color: #ffffff;
}

.badge--free {
  background: var(--color-border);
  color: var(--color-text-muted);
}

/* ----------------------------------------------------------
   Utility Classes
   ---------------------------------------------------------- */
.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;
}

.hidden { display: none !important; }

.flex         { display: flex; }
.flex-col     { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2        { gap: var(--space-2); }
.gap-3        { gap: var(--space-3); }
.gap-4        { gap: var(--space-4); }

.mt-2  { margin-top: var(--space-2); }
.mt-4  { margin-top: var(--space-4); }
.mt-6  { margin-top: var(--space-6); }
.mt-8  { margin-top: var(--space-8); }
.mb-4  { margin-bottom: var(--space-4); }
.mb-6  { margin-bottom: var(--space-6); }
.mb-8  { margin-bottom: var(--space-8); }

/* ----------------------------------------------------------
   Responsive
   ---------------------------------------------------------- */
@media (max-width: 640px) {
  :root {
    --text-4xl: 1.875rem;
    --text-3xl: 1.5rem;
  }

  .container {
    padding-inline: var(--space-4);
  }

  /* Mobile header: hide text nav links, keep upgrade button */
  .site-header__nav a:not(.btn) {
    display: none;
  }

  .site-header__nav {
    gap: var(--space-3);
  }

  .site-footer__inner {
    flex-direction: column;
    align-items: flex-start;
  }
}