:root {
  /* Brand Colours */
  --brand-green: #2ECC71;
  --brand-green-dark: #27AE60;
  --brand-green-light: #E8F8F0;
  --brand-dark: #2C3E50;
  --card-dark: #2D3436;

  /* Neutrals */
  --white: #FFFFFF;
  --off-white: #F8F9FA;
  --grey-100: #F1F3F5;
  --grey-200: #E5E7EB;
  --grey-300: #D1D5DB;
  --grey-400: #9CA3AF;
  --grey-500: #6B7280;
  --grey-600: #374151;
  --grey-700: #374151;
  --grey-900: #1A1A2E;

  /* Plugin Aliases */
  --green: #2ECC71;
  --green-dark: #27AE60;
  --green-light: #E8F8F0;
  --navy: #1A1A2E;
  --gray-600: #374151;
  --gray-400: #9CA3AF;
  --gray-200: #E5E7EB;
  --gray-100: #F1F3F5;
  --text-main: #1A1A2E;
  --text-muted: #374151;
  --text-light: #6B7280;
  --border-color: #E5E7EB;
  --nav-height: 72px;

  /* Accent */
  --accent-purple: #8B5CF6;
  --gold: #F4B400;

  /* Subject Colours */
  --subject-maths: #F4B400;
  --subject-physics: #9B59B6;
  --subject-chemistry: #2ECC71;
  --subject-biology: #3498DB;
  --subject-further-maths: #E67E22;

  /* Typography */
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

  /* Spacing */
  --section-padding: 80px;
  --section-padding-mobile: 48px;
  --container-max: 1200px;
  --container-narrow: 800px;
  --container-padding: 24px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.08);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);

  /* Borders */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --border-light: 1px solid #E5E7EB;
}

/* =============================================
   RESET & BASE
============================================= */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: #6B7280;
  background: #F8F9FA;
  -webkit-font-smoothing: antialiased;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}
main {
  flex: 1;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
ul { list-style: none; }

/* =============================================
   TYPOGRAPHY
============================================= */
h1 { font-size: 48px; font-weight: 700; line-height: 1.2; color: #1A1A2E; }
h2 { font-size: 32px; font-weight: 700; line-height: 1.3; color: #1A1A2E; }
h3 { font-size: 24px; font-weight: 600; line-height: 1.3; color: #1A1A2E; }
h4 { font-size: 20px; font-weight: 600; line-height: 1.4; color: #1A1A2E; }
p { color: #6B7280; line-height: 1.6; }

/* =============================================
   LAYOUT UTILITIES
============================================= */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section-pad { padding: 80px 0; }
.section-pad-lg { padding: 120px 0 80px; }
.text-center { text-align: center; }
.section-label {
  display: block;
  font-size: 14px;
  font-weight: 600;
  color: #6B7280;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 12px;
}
.section-header {
  text-align: center;
  margin-bottom: 48px;
}
.section-header p {
  color: #6B7280;
  font-size: 16px;
  margin-top: 12px;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.6;
}
.section-subtitle {
  font-size: 18px;
  color: #6B7280;
  max-width: 600px;
  margin: 16px auto 0;
}

/* =============================================
   BUTTONS
============================================= */
.btn, .btn-primary, .btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 16px;
  font-weight: 600;
  border-radius: 8px;
  padding: 14px 28px;
  cursor: pointer;
  border: none;
  font-family: inherit;
  transition: background 0.2s ease, box-shadow 0.2s ease, transform 0.2s ease;
  text-decoration: none;
  white-space: nowrap;
}
.btn-primary {
  background: #2ECC71;
  color: #fff;
}
.btn-primary:hover {
  background: #27AE60;
  box-shadow: 0 4px 12px rgba(46,204,113,0.3);
  transform: translateY(-1px);
}
.btn-secondary {
  background: transparent;
  color: #2ECC71;
  border: 1px solid #2ECC71;
}
.btn-secondary:hover {
  background: #E8F8F0;
  transform: translateY(-1px);
}
.text-link {
  color: #2ECC71;
  font-weight: 500;
  font-size: 15px;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  transition: opacity 0.2s ease, gap 0.2s ease, color 0.2s ease;
}
.text-link:hover { opacity: 0.8; gap: 8px; color: #27AE60; }

/* =============================================
   CARDS
============================================= */
.card {
  background: #fff;
  border: 1px solid #E5E7EB;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
  padding: 24px;
  transition: box-shadow 0.2s ease, transform 0.2s ease;
}
.card:hover {
  box-shadow: 0 8px 24px rgba(0,0,0,0.1);
  transform: translateY(-2px);
}

@media (max-width: 768px) {
  h1 { font-size: 34px; }
  h2 { font-size: 26px; }
  h3 { font-size: 20px; }
  .section-pad { padding: 48px 0; }
  .section-pad-lg { padding: 48px 0; }
}