This game is very worthy of the title "Good old game". I owned it on steam but wanted to get the dlc and decided I should get it on GOG as well since it is more customer-friendly. This game is a blast. You learn how orbital mechanics work, and you have to test and change your rocket designs to get it to do what you need it to. You will fail. A lot. But each time you do, you learn what works and what doesn't. This game is a lot of fun and the modding community is massive. Highly reccomended if you like engineering of any kind.