Pico-8 is (AFAIK) the program that kicked off a trend of simple game engines, and it is by far the most popular. A popular game that came out this year, Celeste, was originally a Pico-8 game that proved popular enough to remake in a more modern game engine. Pico-8 supports a Lua API, with a built-in graphics editor for 8x8 sprites, and a 4-channel audio editor. Games can be exported as a PC/Mac/Linux binary, into HTML+JS for embedding into a webpage, and even as a PNG for easy sharing to other users with the Pico-8 program. There's also a very active BBS where 'cartridges' can be shared and played online: https://www.lexaloffle.com/bbs/?cat=7#mode=carts
I'm a relatively novice programmer, and one of the things that frustrated me was how difficult it was to make a simple game on modern machines. I didn't want to have to set up a whole Unity project or dive into OpenGL just for a little proof of concept. I've been heavily using Pico-8 and really recommend it for simple game programming. There's also a hashtag on Twitter (if you're into that sort of thing), #pico8, where people try to create interesting visual code golf programs that fit into the size of a Tweet, then they post the source code and a gif.