Soak-off gel polish is pretty hot right now, but it can get more fun with the mood changing colors. It is temperature activated. If you go from hot to cold, or vise versa, the color(s) on your nails will change from one color to the other.
Unless you are a shark, mood gel polishes will give that ombre look. Your nail bases are usually warmer than the tip of your nails, therefore it will remain one color and your tips will change to other color. It will be fun to see it changing when you wash your hands in water with different temperatures too. It will continue to go back and forth until your next manicure. Pretty cool stuff!