I've now played the game in more detail, against the cpu-opponent and it's definitely fun. Good work! In my eyes, the computer-opponent could play a bit stronger, because I now regularly beat him, even on the "hard" setting. Maybe in a future v1.1, a “superhard” mode can be added, that would be nice for experienced players.
And a second suggestion. For sure, the most players will use a controller for the game (joystick/gamepad), so it would probably make sense, to leave the setting "joystick" by deafult, in the game-menue for "F7 controls". If anyone wants to play with the keyboard, they can change it there, but as the default-setting, always this should be set in the menue, what the most people will use.
Overall, nice game.