/* ============================================================
   BASE.CSS — Synapse AI: "AI, First Steps"
   Brand system, reset, typography, shared utilities
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,400;0,700;1,400&family=Lato:wght@300;400;700;900&display=swap');

/* ── Brand Tokens ─────────────────────────────────────────── */
:root {
  /* Colours */
  --dark-green:   #192D14;
  --mid-green:    #2E5E30;
  --light-green:  #8DC63F;
  --cream:        #F0EDE0;
  --cream-dark:   #E5E1D0;
  --white:        #FFFFFF;
  --grey:         #777777;
  --grey-light:   #EBEBEB;
  --grey-dark:    #444444;
  --error:        #C0392B;
  --success:      #27AE60;
  --warning:      #F39C12;

  /* Typography */
  --font-heading: 'Playfair Display', Georgia, serif;
  --font-body:    'Lato', -apple-system, sans-serif;

  /* Spacing scale */
  --space-xs:   4px;
  --space-sm:   8px;
  --space-md:   16px;
  --space-lg:   24px;
  --space-xl:   40px;
  --space-2xl:  64px;

  /* Radii */
  --radius-sm:  4px;
  --radius:     8px;
  --radius-lg:  16px;
  --radius-xl:  24px;

  /* Shadows */
  --shadow-sm:  0 2px 8px rgba(0,0,0,0.08);
  --shadow:     0 4px 24px rgba(0,0,0,0.12);
  --shadow-lg:  0 12px 48px rgba(0,0,0,0.20);
  --shadow-xl:  0 24px 80px rgba(0,0,0,0.30);

  /* Transitions */
  --ease:       0.2s ease;
  --ease-slow:  0.4s ease;

  /* Layout */
  --sidebar-width: 280px;
  --nav-height:    64px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-body);
  font-weight: 400;
  line-height: 1.6;
  color: var(--grey-dark);
  background: var(--cream);
  min-height: 100vh;
}

img { max-width: 100%; display: block; }
a  { color: inherit; text-decoration: none; }
ul, ol { list-style: none; }
button { cursor: pointer; border: none; background: none; font-family: inherit; }
input, textarea, select { font-family: inherit; }

/* ── Typography ───────────────────────────────────────────── */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  line-height: 1.2;
  color: var(--dark-green);
}

h1 { font-size: clamp(1.8rem, 4vw, 2.8rem); font-weight: 700; }
h2 { font-size: clamp(1.4rem, 3vw, 2.0rem); font-weight: 700; }
h3 { font-size: clamp(1.1rem, 2vw, 1.4rem); font-weight: 700; }
h4 { font-size: 1.1rem; font-weight: 700; }

p   { margin-bottom: var(--space-md); }
p:last-child { margin-bottom: 0; }

strong { font-weight: 700; color: var(--dark-green); }
em     { font-style: italic; }

/* ── Shared UI Components ─────────────────────────────────── */

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 12px 28px;
  border-radius: var(--radius);
  font-family: var(--font-body);
  font-size: 0.95rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  transition: all var(--ease);
  white-space: nowrap;
}

.btn-primary {
  background: var(--light-green);
  color: var(--dark-green);
}
.btn-primary:hover {
  background: #7AB535;
  transform: translateY(-1px);
  box-shadow: var(--shadow);
}

.btn-secondary {
  background: transparent;
  color: var(--light-green);
  border: 2px solid var(--light-green);
}
.btn-secondary:hover {
  background: rgba(141,198,63,0.1);
  transform: translateY(-1px);
}

.btn-dark {
  background: var(--dark-green);
  color: var(--cream);
}
.btn-dark:hover {
  background: var(--mid-green);
  transform: translateY(-1px);
  box-shadow: var(--shadow);
}

.btn-ghost {
  background: transparent;
  color: var(--grey);
  padding: 8px 16px;
}
.btn-ghost:hover { color: var(--dark-green); }

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

.btn-full { width: 100%; }

.btn-sm {
  padding: 8px 18px;
  font-size: 0.85rem;
}

.btn-lg {
  padding: 16px 36px;
  font-size: 1.05rem;
}

/* Form elements */
.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-xs);
  margin-bottom: var(--space-md);
}

.form-label {
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  color: var(--grey);
}

.form-input {
  width: 100%;
  padding: 12px 16px;
  border: 1.5px solid var(--grey-light);
  border-radius: var(--radius);
  font-size: 1rem;
  color: var(--grey-dark);
  background: var(--white);
  transition: border-color var(--ease), box-shadow var(--ease);
  outline: none;
}

.form-input:focus {
  border-color: var(--light-green);
  box-shadow: 0 0 0 3px rgba(141,198,63,0.2);
}

.form-input::placeholder { color: #BBBBBB; }

.form-input.error { border-color: var(--error); }

.form-error {
  font-size: 0.82rem;
  color: var(--error);
  display: none;
}
.form-error.visible { display: block; }

/* Cards */
.card {
  background: var(--white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  padding: var(--space-xl);
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 20px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.3px;
}

.badge-green {
  background: rgba(141,198,63,0.15);
  color: var(--mid-green);
}

.badge-grey {
  background: var(--grey-light);
  color: var(--grey);
}

.badge-cream {
  background: var(--cream-dark);
  color: var(--mid-green);
}

/* Progress bar */
.progress-bar {
  height: 8px;
  background: var(--grey-light);
  border-radius: 99px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--mid-green), var(--light-green));
  border-radius: 99px;
  transition: width 0.6s ease;
}

/* Divider */
.divider {
  border: none;
  border-top: 1px solid var(--grey-light);
  margin: var(--space-lg) 0;
}

/* Alert / notice box */
.alert {
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius);
  font-size: 0.9rem;
  margin-bottom: var(--space-md);
  display: none;
}
.alert.visible { display: block; }
.alert-error   { background: #FDE8E8; color: var(--error); border-left: 3px solid var(--error); }
.alert-success { background: #E8F8EF; color: var(--success); border-left: 3px solid var(--success); }
.alert-info    { background: rgba(141,198,63,0.1); color: var(--mid-green); border-left: 3px solid var(--light-green); }

/* Callout boxes (used in chapter content) */
.callout {
  padding: var(--space-lg);
  border-radius: var(--radius);
  margin: var(--space-xl) 0;
  border-left: 4px solid;
}

.callout-key {
  background: rgba(141,198,63,0.08);
  border-color: var(--light-green);
}
.callout-key .callout-title { color: var(--mid-green); }

.callout-warn {
  background: rgba(243,156,18,0.08);
  border-color: var(--warning);
}
.callout-warn .callout-title { color: var(--warning); }

.callout-info {
  background: rgba(25,45,20,0.05);
  border-color: var(--dark-green);
}

.callout-title {
  font-family: var(--font-heading);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: var(--space-sm);
}

/* Data tables (used in course content) */
.data-table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-xl) 0;
  font-size: 0.9rem;
}

.data-table th {
  background: var(--dark-green);
  color: var(--cream);
  padding: 10px 16px;
  text-align: left;
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 0.8rem;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.data-table th:first-child { border-radius: var(--radius-sm) 0 0 0; }
.data-table th:last-child  { border-radius: 0 var(--radius-sm) 0 0; }

.data-table td {
  padding: 10px 16px;
  border-bottom: 1px solid var(--grey-light);
  vertical-align: top;
}

.data-table tr:nth-child(even) td { background: rgba(240,237,224,0.5); }
.data-table tr:last-child td { border-bottom: none; }

/* Loading spinner */
.spinner {
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255,255,255,0.3);
  border-top-color: var(--white);
  border-radius: 50%;
  animation: spin 0.7s linear infinite;
  display: inline-block;
}
.spinner-dark {
  border-color: rgba(25,45,20,0.2);
  border-top-color: var(--dark-green);
}

@keyframes spin { to { transform: rotate(360deg); } }

/* ── Grid texture overlay (used on dark sections) ─────────── */
.grid-texture::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(46,94,48,0.4) 1px, transparent 1px),
    linear-gradient(90deg, rgba(46,94,48,0.4) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
}

/* ── Utility classes ──────────────────────────────────────── */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0,0,0,0); border: 0;
}
.text-center { text-align: center; }
.text-sm     { font-size: 0.875rem; }
.text-xs     { font-size: 0.75rem; }
.text-muted  { color: var(--grey); }
.text-green  { color: var(--light-green); }
.text-cream  { color: var(--cream); }
.font-heading { font-family: var(--font-heading); }

.mt-sm  { margin-top: var(--space-sm);  }
.mt-md  { margin-top: var(--space-md);  }
.mt-lg  { margin-top: var(--space-lg);  }
.mt-xl  { margin-top: var(--space-xl);  }
.mb-md  { margin-bottom: var(--space-md); }
.mb-lg  { margin-bottom: var(--space-lg); }

.flex   { display: flex; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.gap-sm { gap: var(--space-sm); }
.gap-md { gap: var(--space-md); }

.hidden { display: none !important; }
.visible { display: block !important; }

/* ── Scrollbar ────────────────────────────────────────────── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--cream-dark); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: #CCCAB8; }