In the game you fight different kinds of monsters which are composed of gems in different colors. The only way to defeat them is to match and remove all the gems on their body. Each monster has it's own distinctive behavior and attack mode and you'll need to use different upgrades and skills to contend with them.
Please read the help tips carefully before fighting with monsters, which will help you to enjoy the game.
Now gem monster have 10 distinctive monsters all have 3 levels of difficulty, and will increase to 20 monsters in time.