Laser engrave to your heart’s content with this handy DIY project. If the video player is not working, you can click on this alternative video link. Who doesn’t love a bit of laser engraving?

Optiboot (an older version) is installed by default on the Arduino Uno and (as of 2018) official Arduino Nano boards. It can be installed on all older mega8, 168 or 328 based Arduinos. As of 2019, ...

You mostly do not need to worry about pitfalls of concurrent processing (races, deadlocks, livelocks, resource sharing, etc.). The fact of cooperative processing takes care of such issues by design.