Of course #KerbalSpaceProgram is free today - I bought it 2 days ago. Set up an old laptop for my son - #FloatingSandbox #ScratchJr as well. #KerbalSpaceProgram seems a bigger hit than the much requested #FloatingSandbox (which also seems a one trick pony).

So far he is only launching stock rockets but there's a lot for him to grow into.