Five games as part of Rockman Classic series were released on the Gameboy in 1991 to 1994. The first four games consists of mainly Robot Masters from the original Famicom/NES series. Instead of having eight Robot Masters coming from a single game, they are composed of two groups of four from two games.
For example, Rockman World 1 has four Robot Masters from Rockman 1, then the last four coming from Rockman 2. These games started the trend of having a mid-stage wherein after defeating the first four Robot Masters, a mid-stage boss appears. This was also used in the original numbered series starting with Rockman 7.
This also started the trend of having a shop to buy items. The first game to do this was from Rockman World 4. The currency for that game is the P-chips (which was turned into Screws in Rockman 7 until Rockman 10).
This also marked the appearance of the Rockman Killers namely Enker, Punk and Ballade. Also the of the altered Rockman from the far future, Quint. The Rockman Killers also appeared in Rockman 10 as a part of Special Stages (and their weapons can also be obtained after defeating them). All four robots appeared during the mid-stages.
In Rockman World 5, the Robot Masters are called Star Rulers or Stardroids in the US. They are named after the planets of the solar system. They are also part of Wily's numbered robot series.
Though the Gameboy Rockman series started in 1991, Rock gained new moves as the new games were released. Rockman World 1 was like the first Rockman game, Rock being able to shoot and jump only. The slide was introduced in Rockman World 2. Being able to charge the Rock Buster first appeared in Rockman World 3 (imagine defeating the Rockman 3 Robot Masters with the charged Rock Buster). Rockman World 4 was like Rockman 5 because of the upgraded Rock Buster, but the downside was having a push backwards whenever a charged Rock Buster is fired. Rockman World 5 featured the Rock'n Arm or Mega Arm in the US (the only appearance in the Classic series).
One of the problems of this game is having a very small room to maneuver because of the Gameboy's screen and also Wily's Machines appeared to be smaller than those from the Famicom/NES series. Thus, making the game a little bit harder. I personally don't have the physical cartridges but I do have the emulator of Gameboy/GBA named Visual Boy Advance that's why I played those games without having to buy a real console.
