"Build", "Simple" and "USB" really don't go together. USB is really hard for hobbyists. Leave it alone.
If you need to communicate with a PC, use serial. If you don't have a serial port, buy a cheap USB to serial converter and use that.
It is quite easy to interface a microcontroller with I2C tilt sensors or with stepper motors.
The tilt sensor that I suggested has a range of +/- 2 g. If you mount it horizontally, 40 deg of tilt gives you about 0.6 g. That would use about 1/3 of the available range, which is OK, but not ideal.