/* ── Reset ────────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
img, video, svg { display: block; max-width: 100%; }
input, button, select, textarea { font: inherit; }
ul, ol { list-style: none; }

/* ── Design Tokens ──────────────────────────────────────────────────── */
:root {
  /* Colors */
  --c-bg:             #ffffff;
  --c-bg-subtle:      #f8fafc;
  --c-bg-muted:       #f1f5f9;
  --c-bg-code:        #f1f5f9;
  --c-border:         #e2e8f0;
  --c-border-strong:  #cbd5e1;
  --c-text:           #1e293b;
  --c-text-muted:     #475569;
  --c-text-light:     #64748b;
  --c-heading:        #0f172a;
  --c-primary:        #0ea5e9;
  --c-primary-dark:   #0369a1;
  --c-secondary:      #6366f1;
  --c-secondary-dark: #4f46e5;
  --c-accent:         #10b981;
  --c-accent-dark:    #059669;
  --c-amber:          #f59e0b;
  --c-purple:         #a78bfa;
  --c-red:            #ef4444;

  /* Typography */
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'SF Mono', 'Cascadia Code', 'Fira Code', Consolas, 'Liberation Mono', monospace;
  --text-xs:   0.75rem;
  --text-sm:   0.875rem;
  --text-base: 1rem;
  --text-lg:   1.125rem;
  --text-xl:   1.25rem;
  --text-2xl:  1.5rem;
  --text-3xl:  1.875rem;
  --text-4xl:  2.25rem;
  --text-5xl:  3rem;

  /* Spacing */
  --sp-1:  0.25rem;
  --sp-2:  0.5rem;
  --sp-3:  0.75rem;
  --sp-4:  1rem;
  --sp-5:  1.25rem;
  --sp-6:  1.5rem;
  --sp-8:  2rem;
  --sp-10: 2.5rem;
  --sp-12: 3rem;
  --sp-16: 4rem;
  --sp-20: 5rem;

  /* Radii */
  --r-sm: 4px;
  --r:    8px;
  --r-lg: 12px;
  --r-xl: 16px;
  --r-full: 9999px;

  /* Shadows */
  --sh-sm: 0 1px 2px rgba(0,0,0,.05);
  --sh:    0 1px 3px rgba(0,0,0,.1), 0 1px 2px rgba(0,0,0,.06);
  --sh-md: 0 4px 6px rgba(0,0,0,.07), 0 2px 4px rgba(0,0,0,.06);
  --sh-lg: 0 10px 15px rgba(0,0,0,.1), 0 4px 6px rgba(0,0,0,.05);
  --sh-xl: 0 20px 25px rgba(0,0,0,.1), 0 10px 10px rgba(0,0,0,.04);

  /* Layout */
  --header-height:  64px;
  --content-max:    1400px;
  --content-pad:    clamp(1rem, 4vw, 2.5rem);
}

/* ── Base Typography ────────────────────────────────────────────────── */
body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.65;
  color: var(--c-text);
  background: var(--c-bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: var(--c-primary-dark);
  text-decoration: underline;
  text-underline-offset: 2px;
  transition: color 0.15s ease;
}
a:hover { color: var(--c-secondary); }

/* Sticky-header anchor offset */
:target,
h1, h2, h3, h4, h5, h6 {
  scroll-margin-top: calc(var(--header-height) + 1.5rem);
}

/* ── Task list (markdown-it-checkbox) ───────────────────────────────── */
.task-list {
  list-style: none;
  padding-left: 0;
}
.task-list-item {
  display: flex;
  align-items: flex-start;
  gap: var(--sp-2);
  margin-bottom: var(--sp-2);
}
.task-list-item input[type="checkbox"] {
  width: 1rem;
  height: 1rem;
  margin-top: 0.22rem;
  cursor: pointer;
  accent-color: var(--c-primary);
  flex-shrink: 0;
}