set Y values for obstacles

[mike-duke]

cars should stay in lanes, logs in moat

[mike-duke]

there are 5 car lanes and 5 log lanes with a "rest area" at the bottom, the center, and the top of the screen. between the left and right instances of the cars and the logs, y values can be fixed. frog should come fully into lane and the obstacle should come at the frog head on, no half values.