I still can't get over the RPi, haven't since 2012, and every time I get close they impress me again.
I know there are alternative SBCs out there, but for a pittance you can get something the size of a credit card that can serve so many purposes from a plethora of robotic applications to a full-blown lightweight PC or server substitute, all while running a pretty tight variant of a /very/ common free OS, all very well supported and documented either by RPF or the aftermarket.
I've got or had these things running everything from robotic tea carriers while I was on crutches, to webcams to model railway controllers to IR cameras on rallies to email/web/etc servers to TV alternatives and countless other things beside. It's a fantastic platform for learning, for any age - the original RPi was my gateway to Arduino, ESP etc., while other people have made personal compute clusters, 3D scanners, or put them into use in industry. (I'm pretty sure someone will be churning out RPi4s as VESA-mounted thin-clients pretty soon, if they're not already)
To my mind, it's the closest thing to an utterly universal and accessible computer currently going. Such a wonderful piece of kit.
Beers for all at RPi Towers.