:root {
  --color-primary: #4CAF50;
  --color-primary-dark: #388E3C;
  --color-secondary: #ffffff;
  --color-bg-light: #f9f9f9;
  --color-text: #333333;
  --font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  --border-radius: 8px;
  --transition: all 0.3s ease-in-out;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--font-family);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg-light);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

header {
  background-color: var(--color-primary);
  color: var(--color-secondary);
  padding: 3rem 1.5rem;
  text-align: center;
  font-weight: 700;
  font-size: 2.25rem;
  letter-spacing: 2px;
  text-transform: uppercase;
  box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
}

nav {
  background-color: var(--color-text);
  display: flex;
  justify-content: center;
  padding: 1rem 0;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

nav a {
  color: var(--color-secondary);
  margin: 0 1.25rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 1.125rem;
  padding: 0.5rem 0;
  position: relative;
  transition: var(--transition);
}

nav a::after {
  content: '';
  display: block;
  width: 0%;
  height: 2px;
  background: var(--color-primary);
  transition: width 0.3s ease;
  position: absolute;
  bottom: 0;
  left: 0;
}

nav a:hover,
nav a:focus {
  color: var(--color-primary);
  outline: none;
}

nav a:hover::after,
nav a:focus::after {
  width: 100%;
}

section {
  padding: 3rem 1.5rem;
  max-width: 960px;
  margin: 2rem auto;
  background-color: var(--color-secondary);
  border-radius: var(--border-radius);
  box-shadow: 0 3px 15px rgba(0,0,0,0.05);
}

.hero {
  text-align: center;
  padding: 5rem 2rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  border-radius: var(--border-radius);
  color: var(--color-secondary);
  margin-bottom: 2rem;
  box-shadow: 0 8px 20px rgba(0,0,0,0.15);
}

.hero h2 {
  font-size: 2.75rem;
  font-weight: 800;
  margin: 0;
  letter-spacing: 1px;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
}

.card {
  padding: 2rem;
  background: var(--color-secondary);
  border-radius: var(--border-radius);
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  cursor: default;
}

.card:hover,
.card:focus-within {
  transform: translateY(-5px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

#signupBtn {
  display: inline-block;
  padding: 0.75rem 2rem;
  background-color: var(--color-primary);
  color: var(--color-secondary);
  border: none;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-size: 1.125rem;
  font-weight: 700;
  text-transform: uppercase;
  transition: background-color 0.3s ease, box-shadow 0.3s ease;
  box-shadow: 0 4px 12px rgba(76,175,80,0.4);
  user-select: none;
}

#signupBtn:hover,
#signupBtn:focus {
  background-color: var(--color-primary-dark);
  box-shadow: 0 6px 18px rgba(56,142,60,0.6);
  outline: none;
}

#signupBtn:active {
  transform: scale(0.95);
}

footer {
  background-color: var(--color-text);
  color: var(--color-secondary);
  text-align: center;
  padding: 2rem 1rem;
  margin-top: 3rem;
  font-size: 0.9rem;
  letter-spacing: 0.8px;
  box-shadow: 0 -4px 10px rgba(0,0,0,0.1);
  user-select: none;
}