Caverns of Mars, in case you've never heard of it, sees players guiding a spaceship into a large cavern, blasting away enemies, and collecting fuel to continue the descent. It was originally published as part of the Atari Program Exchange (APX) in 1981 — a division of Atari that sold software via mail-order for Atari 8-bit computers in the early 80s — and was written by the high school student Greg Christensen, with later modifications from Richard Watts of Macrotronics.
It is often credited online as being the best-selling piece of software APX title, and even later became an official Atari product (being distributed first on diskette, and later on cartridge). Since then, it has also appeared on the Atari Flashback 2 game console as one of the pre-installed games and has also served as the inspiration for Caverns of Mars: Recharged — a modern successor for Nintendo Switch, PC, PS4, PS5, and Xbox consoles.
Retro Games, the company behind the Atari 400 Mini, made the announcement that the title had been added to the device earlier today in a blog post, which includes instructions on how to apply the update.
In this blog post, the company also outlined a bunch of additional changes too, including fixes for missing graphics in M.U.L.E, analog stick mapping for 5200 controllers, a Missile Command save state reset issue, and much, much more.
You can read the full blog post here.