KSP is excellent because it makes a lot of attempts to get the physics true to reality. I like that it teaches orbital mechanics to people in such a fun way that people don't know that they're actually learning physics.

Whether or not you learn why it takes less fuel to get to orbit when you turn to East @ 45 degrees of vertical, you know that it does take less fuel.

Whether or not you learn why it takes less fuel to change an orbit at apogee, you know that is the ideal location to do so.