Car Flag tasks a car with driving across a 1D line to the correct flag.
The car must first drive to the oracle flag and then to the correct endpoint.
The agent's observation is a vector of three floats: its position on the line,
its velocity at each timestep, and the goal flag's location when it reaches
the oracle flag. The agent's actions alter its velocity: it can accelerate left,
perform a no-op (maintain current velocity), or accelerate right.

The easy level has the range [-1, 1].
The medium level has the range [-3, 3].
The hard level has the range [-5, 5].