I set myself the goal of writing a CHIP8 emulator before going to bed in one sitting. This is the result. I decided I would be done when the Space Invaders ROM would work. The initial commit reflects that state.
Getting there took about three and a half hours of effective work. I did stray a few times implementing unnecessary (for Space Invaders) opcodes and tidying up the code, but I'm pretty happy about the time I got it done in.
Performance was not a concern at any point (see the QImage backing store travesty).
Needs Qt5 and a compiler that supports C++11.