For those having a difficult time getting the challenge, I find the best start to be: Propeller + 2 upgrades (1200), (Max-1) gas, best wheels, the $200 transmission, and best engine, leaving you with $40. You can get 750+ meters first day with this!
It seems the difficulty increases after the first 10 levels, but after that, it seems quite random... for example, level 16 took me ages, and many of the levels in the 20's were quite easy. overall very fun puzzle game!
to get the points for the dumpster and gold cart, get the bat and the pole vault trick. The trick will give you around 1500 points per use, and if you can get 4 of them off, thats 6k times 2.1 if you have all the groupies. To face the monkey, you have to buy the gold cart and hang glider trick then hang glide and spam space to hit bombs and bananas back at the monkey. To beat the worm, you have to get the dumpster and dumpster dive, then dive while at the top and hold down to get below. Then just spam space again and hit the bombs at the worm until it dies
Nothing is more infuriating than watching corrosive glue not work I'll watch a glued blue balloon go through half the map, not changing to red, and I'll have to use a tack. Developer, please fix this bug, along with changing the fast forward button to toggle off/on, not hold.
A general guide: Life is the most important thing, hence why the "body" upgrades cost the most. This makes the life boost skill the best, so make that one a priority. Make sure the extra penguin skill keeps your summoned penguin approximately the same strength as the rest of your penguins (dont let this skill lag behind the others), and summon him at the opposite side from where the rest spawn. Make sure to have at least 2 bombs, but you dont need any more than 4, because really all theyre good for is killing turtles that penguins stuck behind barriers are targetting. When you buy your 3rd-5th penguin, dont buy all the tiers of armor, it’s a waste of money. For the third penguin, skip tier2 completely (Fighter), and start with tier3 armors. Same goes for 4th penguin (skip to tier4 armor) and the 5th penguin (tier5 armor). As you upgrade penguins, get the "body" piece for all your penguins before getting anything else for any penguin. Rate + so people can see (:
To add to SimpleHarmonic's guide: To use his strategy to its full potential, it is necessary to get lots of HP for all your summons, as well as leveling the Healing Aura+ and Shield Block+ skills. Go for Goblin HP+ first, because they do the tanking in the beginning few rounds (til they die). NEVER SPEND UNNECESSARY POINTS ON THE MAMMOTH TURTLE!! It is the only useless unit. Use your stun spell on the archer towers or the rapid firing archer towers, as your healers will prevent the AOE damage from killing you. Also: get rainbow (top) and circus (far left) ASAP. As a side note: Wave mastery is very helpful, and I doubt spell mastery will ever come in handy, seeing as you only need 1 spell per round using this strategy. Please rate + this comment so people can see!
To add to AioriaRox's comment, it is very important that you have done the story mode first and gotten plenty of Bonus Points, because the hard badge will be impossible to get without MAXING OUT the top right 4 items in the bonus shop (feather, turbo, gas tank, anti-gravity), AS WELL AS the level 2 information meter. The level 2 information reader is what will tell you what your resistance is at. Lastly, For the $25,000 arcade, the angle for the cruise missile you need to maintain ~220 speed is resistance 52. Please + this comment so people can see it!