I love the minigame skill training in this game! Keeps me from having to spend hours fighting lower level enemies just to raise my level high enough to win. I give this game 5/5
If your good enough in the game, you can get the steyr about level 25, only getting the Scorpion or S&W 9mm (I prefer the Scorpion, but the 9mm will work fine.) Guide: Wave 1-3: Save for 9mm (1-10/11 for Scorpion.) Once you got your gun, buy scavenger perk. Waves 12-25 save up, only buying ammo and repairs (or buy builders, they save you alot of needed money.)
I wish (in a future update) that your trimps could fight for you while you are offline. You may miss a few upgrades, but I think it could be totally worth it. Map fragment idea- make super maps that cost quite a chunk a fragment (very easy to obtain with explorers, you only need about 20) and have it give super loot or a special book at the very end.