Heart of Darkness was created and developed by the team responsible for Out of this World. Taking place throughout 127 different locations and eight distinctive worlds, each side-scrolling screen features a unique challenge or puzzle that must be solved in order to progress. Most challenges involve climbing walls, jumping between platforms, and shooting a specific object or multitudes of creatures.
The latter part of that statement is very important to survival; shadow monsters will often attack Andy in droves. Fortunately, he brought along a Plasma Cannon that can be shot in seven different directions. As he progresses through the various worlds and meets up with strange but helpful creatures, ordinary and special powers are learned (sort of like magic).
When he's not destroying hordes of enemies, the hero must navigate the environments carefully. Andy can climb up walls, duck under certain objects, execute long and short jumps, push objects, etc. Each skill must be used accordingly; when there's a small hole to jump across, use the short jump -- using the long jump could prove to be fatal if there's a slew of enemies waiting for you on the other side!