Imagesource: https://github.com/zajo/

The following project is also one of those, that you should have on your most-important-things-in-life-list™, but are not necessarily known to everyone.

We speak about one of the first - if not the first - Apple ][ emulators: Appler.

This very special piece of software was developed in 1990 by Alexander Patalenski (probably @Patalenski on Twitter) and Emil Dotchevski, and runs exclusively on MS-DOS. The special thing about it is, that Appler is written entirely in Assembly and is therefore very fast.

Even cooler is the integrated debugger, which shows the disassembled program, registers, stack and memory, allows stepping, and thus not only makes bug hunting extremely easy, but also helps you to understand the (nowadays considered simple) architecture of the machine.

If you don't have MS-DOS available on hardware, you can also get there with Dosbox. Mac -> Dosbox -> Appler -> Apple ][ ... so much for layer-of-problems™. 🤓