This isn't weird looking. It's what normal MCU code actually looks like.
Arduino code is the weird stuff, with functions that access the MCU control registers indirectly. While this is somewhat "nicer" looking, it's also much slower, and uses a lot more program space.
The mysterious constants are all described in great detail in the ATmega328P datasheet, which you really should read if you're interested in doing anything more then occationally toggling pins on an arduino.