I beat the game mostly on the strength of my rifle. First play through on medium, only had a couple of problems with a couple of maps on their final round. But on hard, I was constantly running on jet fuel, and using my rifle every second I was stopped (except when I was carpet bombing a target area on 3 maps using a maxed cannon). With a well upgraded cannon, you can just hit the high ground and carpet bomb on a lot of maps, but I only found it necessary to win the map on 3 of the missions. On maps where the elves are shooting me from the archery perches, I don't feel it is unfair to give them the same.