Casey Muratori's refterm video series is a great example of how to do application design. It focuses on writing a terminal emulator for Windows, but almost all the concepts apply to nixes as well -- even down to the level of OS primitives like memory mappings to create a ring buffer, etc. He builds a nearly complete terminal that appears to better support unicode and escape sequences than windows-terminal, in drastically less code and with literally orders of magnitude better performance.<p>In particular, I like his focus on experimentation to figure out a reasonable upper bound on performance (so you can measure success/failure), "non-pessimisation" (don't do things extrinsic to the actual task), understanding the actual machine and its capabilities (he doesn't use the term, but sometimes called "mechanical sympathy"), and tactics for isolating "bad code" that you probably have to use (at least to get started).<p><a href="https://www.youtube.com/watch?v=pgoetgxecw8" rel="nofollow">https://www.youtube.com/watch?v=pgoetgxecw8</a>