Since @ragepeanut adviced you to get Game Maker Studio... I can sell you an extra copy I have (of the ver.1.4 the current ver is 2 but it's very expensive) for 1.5 SBD. But I suggest you try the free version of it first because it may be harder than you think.

I also advice you to try Construct 2 it's one of the easiest tools to learn... it's free version is very limited but for a game that will be made in three days only? you probably won't reach those limits.