Unfamiliar but probably System/34 or System/36 running SSP (System Support Program) with IBM 5250 series terminals.

Unsure about the games. Here’s an early lunar lander:

https://www.cs.brandeis.edu/~storer/LunarLander/LunarLander....

Another Lunar version:

https://undefinedvalue.com/lunar-for-c-and-rust.html

System/36 guide:

https://archive.org/details/bitsavers_ibmsystem3rogrammingWi...

Possible source for games in David H. Ahl in his book 101 BASIC Computer Games.