In the meantime there are two ways you can check if you've stopped pressing something.
The first, mentioned by @t1 inspired by how magmaPOP shows how your joystick can return to the center when you let it go. I've linked to the relevant part of the video (minute 13)
The second is from angry birds, inspired by how etalix checked if you let your foot go in Stick Kicking, starting at minute 9:
There are probably many other ways to write this, but these are two good ones! Let me know if this was helpful!
By the way, we love Horizon, it's awesome!