:root {
  --navy: #0a1f44;
  --light-blue: #5aa9e6;
  --light-blue-hover: #85c1f5;
  --sidebar-width: 220px;
  --text: #333;
  --muted: #777;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
}

body {
  background: #ffffff;
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.6;
}

/* Sidebar */

#sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  padding: 2.5rem 1.5rem;
  background: #ffffff;
  border-right: 1px solid #eee;
  overflow-y: auto;
}

#sidebar .brand {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--navy);
  margin-bottom: 2rem;
}

#sidebar ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

#sidebar li {
  margin-bottom: 1rem;
}

#sidebar a {
  color: var(--light-blue);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.95rem;
  transition: color 0.15s ease;
}

#sidebar a:hover {
  color: var(--light-blue-hover);
}

/* Mobile menu toggle button */

#menu-toggle {
  display: none;
  position: fixed;
  top: 1rem;
  left: 1rem;
  z-index: 100;
  width: 44px;
  height: 44px;
  background: #ffffff;
  border: 1px solid #eee;
  border-radius: 8px;
  cursor: pointer;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 4px;
}

#menu-toggle span {
  display: block;
  width: 20px;
  height: 2px;
  background: var(--navy);
}

/* Site header */

#site-header {
  margin-left: var(--sidebar-width);
  border-bottom: 1px solid #f0f0f0;
  padding: 2.5rem 3rem 1.5rem;
  text-align: center;
}

/* Main content */

main {
  margin-left: var(--sidebar-width);
  padding: 2rem 3rem 4rem;
  max-width: 720px;
}

section {
  padding: 3rem 0;
  border-bottom: 1px solid #f0f0f0;
}

section:last-of-type {
  border-bottom: none;
}

h1 {
  color: var(--navy);
  font-size: 3.5rem;
  margin: 0;
}

#home p {
  text-align: center;
}

h2 {
  color: var(--navy);
  font-size: 1.75rem;
  margin: 0 0 0.75rem;
}

section p {
  color: var(--muted);
  margin: 0;
}

/* Footer */

footer {
  padding: 3rem 0 4rem;
}

footer a {
  color: var(--light-blue);
  text-decoration: none;
}

footer a:hover {
  color: var(--light-blue-hover);
}

footer .social {
  margin-top: 0.75rem;
  display: flex;
  gap: 1.25rem;
}

/* Mobile */

@media (max-width: 768px) {
  #sidebar {
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    width: 240px;
    z-index: 99;
    box-shadow: 2px 0 12px rgba(0, 0, 0, 0.08);
  }

  #sidebar.open {
    transform: translateX(0);
  }

  #menu-toggle {
    display: flex;
  }

  main {
    margin-left: 0;
    padding: 2rem 1.5rem 3rem;
  }

  #site-header {
    margin-left: 0;
    padding: 5rem 1.5rem 1.5rem;
  }

  h1 {
    font-size: 2rem;
  }
}