Bubble Bobble World
To play, you leap from platform to platform, dodging foes until you can trap them, and trying to grab all the food and power-up items (amulets, potions, and more) that you can. If an enemy touches you, you die; if you lose all your lives, the game ends. If you survive long enough, you will reach the final level, and victory! (If you survive...)
As in most games of this type, Bubble Bobble world becomes progressively harder--there are more and faster enemies, including some who can attack from afar, the levels are more complex, and the effectiveness of your bubbles wanes. There are also strategies to learn--jump on a rising bubble to reach an otherwise unreachable platform.
Bubble Bobble World is a game which can be learned in under a minute, and, in the full version, offers over a hundred levels of "Just one more try, I know I can beat it" fun. The current version does not work under Vista, and I noticed some slight graphical glitches under XP, but nothing which hindered gameplay.