It's possible to get sort-of stuck in the oasis. If you use the stardust to make the fire but don't remember the rest, you can't go back to the temple and check.
There's a memory leak in here -- slowed down over the course of a session. Check your dereferencing of enemies and coins and make sure you disconnect them from all listeners when they die. If you haven't already, allocate reusable objects for the player's shots ahead of time instead of actively generating them as needed.
In the later levels you need to be able to send the small fry all at once. I can kill skeletons with the splash damage from a single cannonball -- while I can appreciate a wave of 80+ of them to build up funds, why in the name of God are you sending 82 of them SINGLE FILE to pad them out over 6-7 minutes when they're so laughably trivial that their distribution literally does not matter and could be dealt with automatically by the first two rows of spikes, or wiped out en masse by a single shot?
After beating the first boss, the main questline abruptly stops. I feel like NPCs were supposed to show up in the main fortress after that kill, but it was empty except for merchants, and nobody else on the map gives me quests except the faction repeatables.
This actually wouldn't be all that hard if the game wasn't dropping every other jump input. Most of my deaths are because I'm sitting here with my finger on the up button watching my guy randomly decide not to jump for a good second or so.
So is it just me, or do half the upgrades actually impede your ability to get gold scarabs? I mean they're great for basic survival, but they disrupt combos really badly.
Not checkpointing you for crashing is a nice addition, but the game starts out way, way too slow. I mean for a Cyclomaniacs game based around stunts, you're physically incapable of doing any for the first several races.
My one complaint is that when dialogue boxes pop up unexpectedly it's way, WAY too easy to accidentally click past them before you know they're there -- for instance, every time text pops up when you walk up to an item to pick it up. I'd suggest a slight (maybe 1-second) delay on accepting spacebar input for all "sudden" dialogue like that.
I'm not sure why you bothered having more than one or two upgrades. Half the levels were barely possible on Normal, the ones that were conceptually reasonable on Hard/Insane came down entirely to luck with item spawns, and between all of those you're still not going to have enough points for more than a point in speed/armor in Ice Temple. I'd suggest either combining all the snakes' upgrades, because there's not really any point to separating them except for pointless padding.
Is it just me, or do enemies who are about to lose go out of their way to tap a different unit that has no losses yet just to make you waste more stamina in the infirmary?
Your game doesn't even make it past the preloader. I'm gonna go out on a limb and guess that actually making it into the game proper is a paid feature.
 "Memories of you"){kind=icon}
 "The Grey Rainbow"){kind=icon}
 "Siege Knight"){kind=icon}
 "Hands of War 3"){kind=icon}
 "Give Up"){kind=icon}
 "Super Duck Punch!"){kind=icon}
 "Cat God vs Sun King 2"){kind=icon}
 "Cloudstone"){kind=icon}
 "Cyclomaniacs Epic"){kind=icon}
 "Epic Battle Fantasy 4"){kind=icon}
 "Fear Less!"){kind=icon}
 "Bubble Sky"){kind=icon}
 "Shadow Snake 3"){kind=icon}
 "Renegade Racing"){kind=icon}
 "King's Bounty: Legions"){kind=icon}
you worked hard for that money though. =)