Fix flipped controls in "Kernel compiling" minigame

Instead of playing around with rotations, just toggle render_target_v_flip to true, also enable back culling, so the other side is not rendered when it doesn't need to. Replaces !144 (closed).

By the way, in your next commits, you will notice a lot of text being deleted from .tscn files, this is normal, Godot 3.1 now doesn't save default values in them.

Signed-off-by: Michael Alexsander Silva Dias michaelalexsander@protonmail.com