Talk:Custom Game Engine/@comment-108.175.225.20-20130507130758/@comment-9150924-20130507131605

Yes, you have to use it in a game. After you've finished the development of a game, you see the summary popup. Somewhere there it lists the name of the graphics used and the "experience points" gained with it. Develop more games with the selected graphics engine and suddenly there will be a "Level Up!" message appended to the row. After you've reached a certain level (in your case Level 3), you are granted to research further graphics engines.