1 · Slide the rows together

Circles of the same size, arranged in rows. The slider staggers the rows and pulls them closer.

Try this. Push the slider all the way. The circles never change size and none is removed, yet the covered fraction climbs from 78.54 % to 90.69 %.

The covered fraction is computed from the row spacing, which is why it lands exactly on 90.69 % when the rows are fully staggered.