R is usually reload. Only way to reload is to empty your gun. There's also no ammo counter to let you know. As other have said, probably not a good idea to make that restart the level. I'd put that into some kind of ESC pause menu, where I can set volume and stuff. Maybe add some squirrel death sounds...
Anyway, I really liked it. It's a janky meme-ish kind of shooter. That intro video definitely sold me on wanting to play all the way through to the end. Tied it all together. Kinda wished it wasn't 1 hit death, but, it's kinda part of its charm that it is.