body {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  margin: 0;
  background: #f6f7fb;
  color: #202124;
}

/* HEADER */
header {
  background: linear-gradient(90deg, #4285F4, #EA4335, #FBBC05, #34A853);
  color: white;
  text-align: center;
  padding: 40px;
}

/* NAV BAR */
nav {
  display: flex;
  justify-content: center;
  gap: 10px;
  padding: 15px;
  background: white;
  position: sticky;
  top: 0;
  box-shadow: 0 2px 10px rgba(0,0,0,0.08);
}

nav button {
  padding: 8px 14px;
  border: none;
  border-radius: 20px;
  cursor: pointer;
  background: #e8eaed;
}

nav button:hover {
  background: #dadce0;
}

/* MAIN LAYOUT */
main {
  max-width: 1100px;
  margin: 30px auto;
  padding: 10px;
}

/* SECTIONS */
section {
  margin-bottom: 50px;
}

/* SECTION TITLES */
h2 {
  border-left: 5px solid #4285F4;
  padding-left: 10px;
}

/* GRID SYSTEM */
section {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 15px;
}

/* CARDS */
.card {
  background: white;
  padding: 15px;
  border-radius: 10px;
  box-shadow: 0 2px 10px rgba(0,0,0,0.06);
  transition: 0.2s;
}

.card:hover {
  transform: translateY(-4px);
}

/* SECTION COLORS */
.past .card {
  border-left: 5px solid #4285F4;
}

.future .card {
  border-left: 5px solid #34A853;
}

.love .card {
  border-left: 5px solid #EA4335;
}

/* RESPONSIVE */
@media (max-width: 900px) {
  section {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 600px) {
  section {
    grid-template-columns: 1fr;
  }
}