```css

/* multiple track-size values */
grid-auto-columns: min-content max-content auto;
grid-auto-columns: 100px 150px 390px;
grid-auto-columns: 10% 33.3%;
grid-auto-columns: 0.5fr 3fr 1fr;
grid-auto-columns: minmax(100px, auto)    minmax(max-content, 2fr) minmax(20%, 80vmax);
grid-auto-columns: 100px minmax(100px, auto)        10% 0.5fr fit-content(400px);
```