When the PC Engine was first released, NEC and Hudson knew that they would have a hard time tempting third party companies to produce games for the machine - Nintendo's NES was still the number one machine and Nintendo themselves had made many publishers agree to not produce games for their rivals. NEC/Hudson tackled this problem by releasing games that took more than a little inspiration from other successful titles.
There are about a dozen different dungeons to clear in Dungeon Explorer, most of which end with a boss that is harder to get to than to kill. The multilevel dungeons are bursting with creatures for you to kill. The creatures spawn endlessly from portals that you have to destroy, and you'll often find yourself overwhelmed by thick swarms of monsters. All of the fighting and exploring takes place from a top-down perspective, and you can shoot in eight directions.
You can shoot while moving, but you can shoot only in the direction you're moving, which is useless when enemies are coming at you from all sides. It's easier to just pick a spot and shoot until you've killed everything, then move on and do it again a few steps later.
Dungeon Explorer builds on the concept provided by the arcade smash hit Gauntlet, and it actually manages to be a much better game, too. There's more depth, with RPG elements and multiple locations to explore. If you're a fan of Gauntlet then you'll get plenty of enjoyment out of this, even more so if you've got a few like-minded friends.
Tip: You can play 5 players with a gamecube controller for the 5th player, hold down R on the controller whilst booting the game.