Such hard work! First attempt of making such simple behavior we find in every 2D platform game.
Took me a total of like 4 or 5 hours to make this work.
Not proud of the time, but for a first start, I find it quite nice.
I also discovered how to customize the build and make it lighter.
The main challenge here was to make sure that the movement could stop at one moment.
Just to make sure it's clear: for now, only the arrow keys (and WASD on a qwerty keyboard) work.