Since the original game is built in ActionScript (Flash), it can suffer from lag even on modern PCs.
Before we talk about how to play, let’s give credit where it is due. Wrath of the Lamb is not just DLC; it is the definitive way to play the original Isaac. Since the original game is built in ActionScript
For true "high quality," you want to play the game locally, but without installing Steam (which is often blocked). Since the original game is built in ActionScript
If you cannot download files, you need an site. Ruffle is a modern Rust emulator that plays Flash games better than Flash ever did. Since the original game is built in ActionScript