Tarzan was an unreleased Atari VCS/2600 game, sophisticated for the platform but coming as the industry's bubble burst and ultimately issued only for the newer Colecovision. The original materials disappeared, but copies of the game were ultimately found and preserved.
In 2011 a manual for the game turned up, but the game itself remained lost. Lost, that is, until collector Rob "AtariSpot" managed to purchase a working copy of the game off of a former Coleco employee in 2022 and successfully worked with longtime Atari homebrew programmer Thomas Jentzsch to get it dumped. All 2600 games bigger than 4 kilobytes in size utilize an approach called "bankswitching" to get around hardware limitations by inserting code that gets the console to look at a separate 4-kilobyte chunk of data. This allowed for larger and more complex game programs, and Tarzan, a 12-kilobyte cartridge, is no exception. The game uses a unique bankswitching scheme, but Jentzsch was able to modify it into a standard "F6" bankswitch to make it operable on emulators and flash carts.
Want to play it? It's at archive.org in all its chunky-pixeled glory. But be sure to read the rest of the article first, it's a deep dive into how such things were created, then lost, and finally found again.
This is the unreleased Atari 2600 version of Coleco's Tarzan video game, developed by James Wickstead Design Associates and designed by Lawrence Schick. This particular copy came from a former Coleco employee, who sold it to collector AtariSpot. A 12 kilobyte game, this upload includes both the original ROM using a unique bankswitching scheme, as well as a conversion that uses the more common F6 bankswitching scheme, allowing it to readily run on emulators or flash carts.