So glad I came across this, I'd never come across 1st Math! Can't wait to get my kid set up on that. Hoping more people post recommendations in the chat here this stuff is hard to find.

It's lazy but I set my 2yo up with a thinkpad running ubuntu that boots directly into terminal and has a bunch of single-letter aliases to open a few very specific sites including a sketchy in-browser dos emulation running math blaster.

Would have loved to actually just get a dos machine running for him but time starts moving so fast after they're born...

Anyway he's 5 now and still loves getting into some Math Blaster, and it's still providing plenty of challenge for him, I forgot how far it went academically.

Interestingly I think this giving kids this kind of retro software has the positive side-effect of boring kids after a reasonable amount of time. I've been thinking of it as finite media.

He loves Math Blaster but will often choose a physical math workbook instead when its math time, and he stops playing after an hour or so at most so I can just give him unrestricted access to his thinkpad and he organically self-regulates screen-time. Noticed similar effects giving him my old gameboy pocket and an old 8 inch CRT with a built in DVD player and a stack of random Reading Rainbow DVDs. Also using a ThinkPad or Raspberry Pi that struggles at least a little bit with streaming YouTube has helped keep that from getting out of control since I couldn't ultimately avoid youtube for some no-dvd-available science / math / music video stuff.

I highly recommend Eureka, Dirk Niblick, udiprod and Minds Eye.