Eraser. Dotless Puzzle

This is a mathematical puzzle game, which purpose is to remove all points from the game board.
Erase all the dots from the screen using special eraser tiles.
Eraser - snail moves one square per one move.
Eraser - bird per one move moves outside the playing field, erasing all the points on its path.
The switch-button changes all erasers to the opposite ones.
Limited number of moves complicates the tasks.
All the tasks are divided into 5 categories of dimension (4x4, 5x5, 6x6, 7x7, 8x8).
Each group has 1000 levels.
There are total (5x1000) = 5000 tasks.
"Solution" button is available without restriction.