I really don't like how cheap the AI gets on certain enemies. They will have 1 good car and miraculously heal that card and draw it 5 times in a row on a constant basis.
The trick to impossible is having a really low end computer so the frame rate drops to single digits when a lot of stuff goes on. makes it so much easier.
I enjoy the strategy of being able to move units around to fit the situation. Putting strength vs weakness at all times to go much further and timing out the unit abilities.
It just a way to scoring. Don't use it until you are plenty of gold.