my strategies for loki.
1 AMU 3 Valkyrie (my fav) with excalibur. This one depends on your capacity to dodge before u can use the first overdrive. if u manage to get hit only 2 or 3 times u'r ok. just use the overdrive then attack until your chain gets full. get hit then full chain again and get 2nd hit. overdrive again. repeat until finished.
2 - AMU 4 Odin. Hit him hard with excalibur. go invicible hit him hard.. when invicibility ends just circle around throwing everything u've got at him.
Note: Farm money on lvl 19 with time stopper using the strategy described above.
Great game... but liek someone else said, lvl 3 its easy to farm. 2k pops too often.
Last boss is not that hard either, 2 or 3 trys and u get the hang of it. but good game nevertheless 4/5
very simple to achieve all badges..
i used tacks only and then bought a supermonkey uprgrading it to plasma beams.
as for metal bloons and those zeplins stuff.. pineaples..