Anyone has any tips? Does defense/attacks depend on where and when you try to strike? It could use some explanation and solid numbers.

The impression I get when playing the game is that combat is very random.

In the graveyard you need to strike the right & left sides first to disarm the zombies, and then click on the head to cut it off.

Combat in the mine is ridiculously hard. You only have enough HP to survive a fight with one or two mutants using the regular weapons and none of them seem more effective than the other. Use the spray instead.

For the pyramid I'm not so sure. I think the spear is the best weapon and most enemies seem quite easy to kill except the boss. Since it's so random, if you loose a fight with the boss just load a saved game and the next time you might twin regardless of what method you use.