Time Pilot '84: Further Into Unknown World is a 4-way scrolling shoot 'em up, released in 1984 by Konami. It is the sequel to Time Pilot. You pilot your craft over many time periods. Unlike the original, which told you the year of each level, the new time periods are designated by new enemies and different colors.
There are a large number of enemy types in the game. They each have varying movement patterns, difficulty, and point values. Destroying enough standard enemies brings out a boss enemy that must be dispatched before advancing to the next level.
You have two weapons to use on the game's many enemies. Your standard shot can destroy only a couple types of enemy. You need to use your missiles on the remaining ones.
Source: Wikipedia, "Time Pilot '84," available under the CC-BY-SA License.