OK personal experience that worked for me to get what is THEE hardest task towards hard achievement, reach 500m in 30 seconds.
H3 wasp (3rd hull) DS Larva (4th drill) B5 Nova (5th battery)
E5 (5th engine) T4 (4th turbo) S3 energy booster (3rd slot)
All these fully upgraded, the S3 booster is essential to go with B5 battery to help keep boost going this worked for me so thought i'd share hope it helps.
Ok so last boss comes along, big ass flamethrowing dragon, made ofcourse, OF FIRE.. And i kill him with fire arrows and aiming the jumping flameballs in to his face.. Brilliant! :')
I first glance i loved this game.. now i think its a joke.. every chest ive had gives me minor money, $20/30 at most, i can bearly find money to get a weapon cause they keep changing in the shop before ive even had chance to save for a good one, and progressing through the levels is getting so hard because i have crap weapons.. cant even finish the first challenge.. Update this and please do somthing with the bloody money..
Riddle answers
1) family of 9
2) Triangles 27
3) Clock winding 0
4) Sum = 70
These are all located either by a long fence of by a river, just follow them right across. Like if it helps cheers
 "yellow")
 "Absorbed 2")
 "The Splitting")
 "Reach the core")
 "Wild Wasteland")
 "Barons Gate 2")
 "Sky Quest")
 "Epic Boss Fighter")
 "Ultimate Crab Battle")
 "Ultimate Assassin 3")
 "Diggy")
 "The Peacekeeper")
 "Lucky Tower 2")
 "Infectonator 2")
 "Chibi Knight"){kind=icon}
 "Hands of War 2")
 "Particles"){kind=icon}
 "Pinata Hunter")
 "Crush The Castle 2 PP")
 "Crunchball 3000")
^_^