A very simple concept, implemented in an original and smart way!
[SPOILER]
You should replace the "Home" key by another one that can easily be found in compact keyboards. Mine, for instance, does not have that as a single key and I thought I would get stuck because of it. But playing this game made me realise that the "Home" function can actually be triggered by pressing Shift + 7 on the numpad, something I would never otherwise have realised!