The Kerbal space program is a great game.The open world is very big and there are a lot of possibilities.You can fly to the mun, build ISS, build your own rocket or ssto.You can use science method to build rockets.There are many interesting scenarios.In game there are a three modes: career mode, science mode and sandbox mode.I liked the sandbox mode because nothing stops you to do what you want.The Kerbal space program is a beautiful game.l recommend you to play.