Like many others have said, it's got to the point where more and more money is needed to be spent in order to get through levels, even the ones that are classed as 'simpler'. Then, you hit one of the special rounds and as that's a bonus if you get through it, if you don't, you're back to square one again losing all the bonuses you'd built up, then hitting a hard level. Seems a little impossible without spending more and more money. The game itself is fun, shame it's got to the point it has.