Small visual improvements

Today I implemented three new features as small visual improvements:

1) Shop Highlight
Each time you get enough Gold to buy items in the shop the button gets a little red and size flash. This is not the final visual implementation but a fast improvement for the problem lot of people didn't understand hat there's a shop at all.
 

 2) Next Item Preview
Before the first some move animations it's not possible to see which house is the next one in the preview queue. I hope with different ground color it's a fast improvement. I also thought about a little direction arrow... this needs more testing with new players...

3) Same Houses Highlight
If you don't move the selection cursor for some seconds there's a little animation with all houses of the same type. If you get stuck this might help you at the beginning.