[Demisis_P2P]

Three entrances is enough.

And there isn't much you can do about explosives without making them almost completely useless.

It's possible to make it so that you can't place them near doors (the katana was made so that it couldn't slash within 6 tiles of doors once).

But the problem isn't that people put them near doors. The problem is that because Graal is a 2d level based game you can't see what is on the other side of doors. Making it somehow possible to detect or see explosives from the other side of the door is a much better solution than just making arbitrary restrictions.