I also had an early accidental contact with HyperCard, and sort of learned the basics without knowing it. I was looking for something equivalent to show my 12 year old, who is into Minecraft and generally open minded about learning geeky stuff (they've had Sketch and electronics basics in school, likes to plays with LEDs, 3d print, etc). I found Sketch a bit too limited, despite a few attempts, it didn't work out for me.

I don't know much about game programming, but we ended up exploring Unity 3D. There are tons of videos online, it works well under Linux, and you can do lots of different things with limited programming. Probably not perfect, it's just for playing around, but curious to hear other experiences.