1. Dragon curve misses first turtle.go before starting turns (or last go after finishing turns). See video for cases 1 and 2.
2. Dragon curve should be within the window boundaries
3. Program should validate user input to only allow integer values of 0 or higher
4. Program does not print total distance traveled by turtle
5. Dragon curve: creating turns list should avoid duplicate calls to turns(depth-1). Instead copy the resulting list, then reverse, and flip that copy.