Hi mizatorian,
thanks for playing =)
it is auto generated, in the end is very simple mechanic
i made with godot, every level a create a grid, for example 3x3
iterate over the grid and add one block random generated (the size of each block is always the same)
i check if it is the last line and add one block with the end door
for every level i get the dimension (1, 2, 3, etc) and multiply 20% in the enemy velocity