My first GOTD post of the "not posting every day" era, Nightmare in the Dark is a quasi-unique game where you fight monsters on single-screen mazes/structures. The closest game I can say it plays like is Dig Dug - although it doesn't look or feel anything like it and is almost 20 years newer.
How you kill the monsters is where it is like Dig Dug. You hit them with fire once and they stop in place and catch fire... then you have to bombard them with more fireballs until they are engulfed in flames and finally turn into a complete fireball. This action of continuously throwing the fire once they are stymied until they finally become fireballs is just like blowing up the enemies in Dig Dug. And, as you could probably guess, if they are on fire and you don't finish them off, eventually the fire goes out and they start attacking again. Diff monsters require diff numbers of hits before they become fireballs.
Now then, once they are fireballs, you touch them and they follow you wherever you go until you push the fire button again. When you do, the fireball is launched and destroys everything in its path. In fact, you can complete whole levels by burning one monster at the top of the screen and then throwing the fireball, subsequently destroying everything else on the way down.
There are lots of power-ups, but they are incremental (not diff weapons). Your fire can get longer range, stronger and bigger fire and quicker reload, among other things. There are also many treasures to collect that increase your score and health/lives. In fact, many things can be destroyed that toss goodies all over the place - especially at the end of rounds - so you only have a few seconds to collect as much as you can before you are swept off to the next level.
Every 5 levels, a boss appears. Interestingly, you can't kill the bosses directly with your fire. You have to burn their minions and then use the fireballs created to attack the boss. It's a nice touch to add to the difficulty.
As it is from 2000, the graphics are part of what makes the game fun. They are detailed and spooky/fun. Each five levels, after you defeat the boss, you are taken to a different world with diff monsters to burn.
NITD is a nicely paced but not frenetic game that will keep you engaged for a while.
By the way, this was Gavaking/Eleven's only published game (it was for SNK's Neo Geo MVS system).