Thank you Mark.
Good idea for the tutorial about abilities ! I understand why it's necessary.
I will make the help screen better. I admit I did it quickly.
Yes level 4 is very hard. The big difficulty I have now it's to make level with gradual difficulty as you said. I have never realized how difficult it is to make levels .... I can make a new level in 5 minutes, but to find if it's a good level, it's not easy. The only way I found is to test those level with real users.
Yes no sound for the moment I need to find someone who can help me.
Thank you a lot for your useful feedback !