Just like some people said before, investing in weapons other than the short sword and the bow are not a necessity in the game at all, but I'm okay with that sine in my opinion, that's the game's point ( and name). You decide whether to upgrade other weapons or not, and it seems to be just fine to me. Gameplay is nice and it really kept me addicted until I finished everything.
A good sequel would be a futuristic one. I'm expecting cool laser towers and high tech weaponry.. perhaps it could even take place on another planet!