Thanks, all very useful feedback!
Targetting reticule is a good idea, I think you might have had trouble with the aiming because it projects the mouse positition on to the ground plane, which might be a bit low. Perhaps projecting on to the mid-height of the enemies would be more natural. Either way a reticule would help give feedback to adjust.
Enemies are one area that I think is a bit lacking. The logic for them is very simple, with just a radius to the player and some simple move towards the player logic. I had intended to make use of raycasting line of sight for each enemy, but ran out of time before submitting. I would also like to add navmeshes at some point to prevent them getting stuck.
I agree that I really should have exported a web version, I did try it and ran in to a few problems getting it running locally on my machine and was running low on time. It might be worth me trying again when I do the update release after voting ends.