Very hard to pass the 23th level.
My guess the princess that let you accumulate the time should come early, maybe before the gold princess.
So far my strategy:
start
- at the start, push twice to get the wave early (2 infantry) so they will smash the egg, while you rush the grass and easily made a couple of sheep.
- focus on the wolf production till the point they jump
- then balance the sheep production and the grass.
combat
- to maximise the money and the flame, I wait one wave then I rush the following one, to flame 2 waves at the time
- swap the green princess to get the damage reduction and the active spell
princesses
- gold princess useless, you need too much money to benefit of the bonus. Don't go below 10k, trying to keep 20k
- green princess spell swap
- fire princess spam fear managing the timing with flame and green spell
- air princess so far I couldn't benefit enough, for the damage you need a strong sheep output.
What about introduce later some hidden chain quests? I.e. building the quest in a special order(1-cave,2 not important, 3 not important, 4 mountain etc), can lead to a special treasure. The player will not know the right order, but he can receive some soft clues to address it. The chain can be random generated every time the game is reset, to keep a sense on the feature, and the system can be progressive (es. if I solve the first chain, I have access to the second one).
It would be good the idea of the prestige class, I.e. the cleric can learn how to resurrect, the mage a summon, the adventurer how to pickpocket.
In the very future it can be decided the alignment, with bad, good or neutral quest (it can be combined to the chain system, when the good guys have to do a bad but inevitable action).
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