Great game concept, and it was kind of you to put other keyboard layouts! I use the Dvorak layout and always find it difficult for playing games when they have fixed KB layouts such as the asdw model for controls.
Your game concept is really innovative and interesting for the TD genre, but also it offers some quite difficult challenges such as the sometimes too fast minions' movement.
I found it a bit laggy too, but still don't know wheter it's my PC or the Unity requirement. Gonna try it at home later.
Overall, nice job! It'd be nice to see either a more 'retro' version with possibly some 'skins' (greyscale/green/yellow/TANDY /VGA etc etc monitors), and theme enemies (coffee drops, lint, bread crumbs, you know, some of our keyboards' foes lol).
Thumbs up!