/* ===== Base Styles ===== */
:root {
  --primary-color: #3498db;
  --secondary-color: #2ecc71;
  --dark-color: #2c3e50;
  --light-color: #ecf0f1;
  --font-main: 'Arial', sans-serif;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: var(--font-main);
  line-height: 1.6;
  color: #333;
  background-color: #f9f9f9;
}

/* ===== Typography ===== */
h1, h2, h3, h4 {
  margin-bottom: 1rem;
  line-height: 1.2;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.75rem; }
h4 { font-size: 1.5rem; }

a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s;
}

a:hover {
  color: var(--dark-color);
}

/* ===== Layout ===== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1rem;
}

/* ===== Navigation ===== */
header {
  background-color: var(--dark-color);
  color: white;
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

nav ul {
  display: flex;
  list-style: none;
  justify-content: space-between;
}

nav a {
  color: white;
  padding: 0.5rem 1rem;
}

nav a:hover {
  background-color: var(--primary-color);
  border-radius: 4px;
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  background: var(--primary-color);
  color: white;
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  transition: background 0.3s;
}

.btn:hover {
  background: var(--dark-color);
}

/* ===== Cards ===== */
.card {
  background: white;
  border-radius: 8px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

/* ===== Footer ===== */
footer {
  background: var(--dark-color);
  color: white;
  text-align: center;
  padding: 1.5rem 0;
  margin-top: 2rem;
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
  nav ul {
    flex-direction: column;
    align-items: center;
  }

  .container {
    padding: 0 0.5rem;
  }
}