❏　Play more makes it more challenging
In some stages, you have to make 6 as 9 and vice versa, reverse plus and minus and many other tricks are included.

❏　Unlock bonus Stages
As you clear the regular stages, you can unlock some bonus stages such as Time Attack mode and Endless Level mode.
If you connect Dr. SUM with your Facebook account, you can post your high score and you can see how your friends are doing on Friends Leaderboard.