Tap and drag on any numbered circle to extend it. If there's a number on the end of a row, that row needs to have that many circles. If the number is on top of a column, the column needs to have that many circles.

Tap the "Zoom" button to zoom in and tap it again to zoom back out.

If you get stuck, tap the rotating arrow to restart.

If you want to play in Dark Mode, tap on the level select grid, then tap on the circle on top to change the theme.