CSS Grid Layout

.container {
  display: grid;
  
  /* Create three columns: 1st takes 200px, 2nd & 3rd share the rest equally */
  grid-template-columns: 200px 1fr 1fr;
  
  /* Create two rows of 100px and 200px */
  grid-template-rows: 100px 200px;
  
  /* Space between grid items */
  gap: 1.5rem;
}

Grid Lines:
1          2          3          4
├──────────┼──────────┼──────────┤  Row Line 1
│  Item 1  │  Item 2  │  Item 3  │
├──────────┼──────────┼──────────┤  Row Line 2
│  Item 4  │  Item 5  │  Item 6  │
└──────────┴──────────┴──────────┘  Row Line 3

.hero-item {
  /* Starts at column line 1, spans to column line 3 */
  grid-column: 1 / 3;
  
  /* Starts at row line 1, spans to row line 2 */
  grid-row: 1 / 2;
}

/* Shorthand using span keyword */
.sidebar {
  grid-column: span 1; /* Spans 1 column track */
  grid-row: span 2;    /* Spans 2 row tracks */
}

.responsive-card-grid {
  display: grid;
  /* Columns will be at least 250px, but will grow to share space equally */
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2rem;
}

.page-layout {
  display: grid;
  grid-template-columns: 240px 1fr;
  grid-template-rows: auto 1fr auto;
  grid-template-areas:
    "header header"
    "sidebar main"
    "footer footer";
  height: 100vh;
}

header { grid-area: header; }
aside { grid-area: sidebar; }
main { grid-area: main; }
footer { grid-area: footer; }