You are given a 20x20 board with some black blocking pieces. You place your squares by clicking the top left and bottom right positions for such a square. Squares must be size 2x2 or larger.
However, all white cells count as 1x1 squares as well (but you don't have to paint them)!

A square cannot contain a block.
When you have filled the board this way, the number of squares used should be as small as possible.
The right border shows the target and the square counter. Since all empty squares count as 1x1 squares, the counter starts at about 400 (400 minus the number of blocking pieces). The counter will decrease with every square you place.
You win when the counter reaches its smallest value.

You can delete an existing square at any time by clicking the same position twice.

Solutions are given for all variants with fixed setup.
All solutions have been found by hand; so you might be able to improve on them.

Variants:
There are 27 fixed setups and 4 variants with random setups.
The solutions have been found by hand; so you might be able to improve on them.

Please note that there are several alternative piece sets.

Despite being similar to its fore-runners, 'Square Fit III' puts a new twist on this problem type. In fact, its variants are more difficult to solve than the ones in 'Square Fit II'.

Related games: 'Area', 'Area For Two', 'Square Down', 'Square The Square', 'Square The Square II', 'Square Fit', 'Square Fit II'.