Thanks ! The matter is that I need difficult levels...
A level can be 40*20 blocks big. (It's often around 16*12 blocks)
This game is a puzzle game, like the chip's challenge.
The rabbit, Bobby, has to eat all the carrots and reach the end of the level.
There are several kinds of blocks (Hard to explain with my poor English) :

A : Bobby has to reach this target when he has eaten all the carrots.
Z : Bobby cannot walk on these blocks. Kind of walls.
E, R, T, Y, U & I : These blocks rotate 90° clockwise when Bobby leaves them.
O & P : Bobby can walk on them only once. When he leaves a "O" block, the block becomes a "P" block. The "P" block is also a wall.
Q : Bobby has to eat them all.
S : The "S" block is a button, when Bobby push it, all the "E", "R", "T", "Y", "U" & "I" blocks rotates 90° clockwise, all the buttons are inverted. (All the "S" become "D" and all the "D" become "S")
D : Button down. Bobby cannot use them, but "S" buttons can invert them.
F : Empty. Bobby can walk on them.
You can see them in this videoIn the first post, you can download a level creator for your computer, but it's not really convenient... (You can't edit created levels)