This bootcamp relies heavily on the excellent Falstad simulator. Many -- but not all -- of the examples are straight from the simulator's circuits menu or modified from that source.

You should know that the simulator doesn't do just digital electronics. In fact, that's probably the least of its capabilities. It also can model DC, AC, and even RF circuits.

While it won't help you in the FPGA world, if you wondered how things like NAND, OR, and XOR gates are actually built from devices, it is worth checking out the Falstad Circuits menu under logic families. TTL and CMOS are the most useful to look at and you'll see how fundamental gates are made from basic devices. You don't need to do this to progress through this bootcamp, but if you are interested and have a good grounding in transistors (no pun intended), it is a fun detour.