On each level, you try to avoid the monsters, and stock up on the gems and whips that you need to survive. (One or more gems are lost every time you hit a monster, and if you lose all your gems, you die on the next hit; the whip can clear away monsters and crumbled walls in your way.) You may also find other useful things, like keys to unlock doors. At the bottom of the dungeon, a great treasure awaits for the daring and skillful adventurer who makes it.
You can save a game in progress in order to resume after an interruption or have several tries at a tough level without retracing all previous levels. However, only the status as of the beginning of the current level is saved; anything you did after you entered the level won't be saved. You've got to make
it to the end of the level and save again for your later gains to be preserved.