Optimization means reducing the app size with various means. In my work I present ways to optimize 2D-mobile game graphics both from technical and visual point of view. The work is based on State of Matter -mobile game project, in which I worked as a graphic designer. The objective of the work is to clear the meaning of optimization and explain the ways to optimize 2D-graphics. I also describe a bit about the designing progress of State of Matter’s graphics. I used Internet sources as the knowledge basis of my work, and especially the websites of the Unity game engine. Because we used Unity in the State of Matter -project, the main focus of the work is mobile game graphics optimization in Unity. I also sent some questions to professional mobile game graphic designers, whom explained about their own experiences with optimization. The interviewees also told about their own opinions of the significance of graphic optimization in a game project. They also gave some advice about optimization, and tips to people who are interested in the work of a mobile game graphic designer. In my work it transpires that optimization should be performed in all the stages of the game project, from designing to testing and even after uploading the game to app store. There are multiple techniques to optimization, but you can’t find one true way to do it, since every project needs their own technical means. The technical ways of optimization change fast as the hardware improves and widen yearly.