PICO-8 [1], a "fantasy video game console" might be good. It simulates something kinda like a C64, with Lua, tile and sound editors, etc. It's not as simple as Hypercard, but it comes with a number of examples and it's relatively easy to get something interesting moving around on the screen.
1. https://www.lexaloffle.com/pico-8.php
It's inspired a number of similar projects such as TIC-8 and Pixel Vision 8.