Crystal Caves! I've been trying to remember the name of that game for ages! I never bought the full version but played the shareware endlessly...

There's a (presumably) excellent modern port of it a available on Steam: https://store.steampowered.com/app/1330890/Crystal_Caves_HD/

I say presumably because I played their excellent Secret Agent HD port but haven't played Crystal Caves yet.

There are also infinite clones of it. But I'm not aware of any open source one yet

$1k in 1990 ~= $2.5k today.

And that would get you a system that was fairly anemic even for then. There were still some 286 systems being sold then which was 2 full architecture leaps behind at a time when it was starting to become very important.

> You could get a PC for a thousand bucks back then

In the United States... In a lot of countries, computers cost a lot more than that in the local currency which, together with lower salaries, made computers inaccessible to most people.

I remember seeing people playing GORILLA.BAS in computer stores...

Which is why in many countries we stayed on the Speccy and C64, until 386SX were already widespread.