Well, and didn't gameplay teach you the rules? Do anything with enemies to kill them, go to the exit to win. Those are the rules.
It's a matter of putting extra effort if you want the better ending, which isn't mandatory, it's just a more challenging and fun way of experiencing the game.
I'm all defensive now, but in fact I want to know where exactly the bad design is, because you didn't point it out clearly.
Viewing post in Rogue I Don't Like jam comments
I'll break the enemies down for you:
The brown ones rush at you
the blue ones don't care about you, but when you get close they shoot lightning
the red ones start murdering other enemies when they see you
The other "attacks" are obviosly useless... When you're going for the bad ending. To get the good ending, you need not a single enemy to die during a run. To know that, you need to pay a little bit of attention during the bad ending and ask yourself - why are there those seemingly useless spells?
You've had the clues before you the whole time.
And once you start trying to get the good ending... Let's say the explosion spell becomes the least useful all of a sudden.
It's in the spirit of roguelikes to have secrets, but I think the ending guy nagging you about your killings, and the whole fact that the game is suspiciously easy to get through should hint at the pacifist route. But you may be right, I may have made this too criptic for jam standards.
Thanks a lot for the discussion!