I come up with the answer of "6 + 9" easily, but for some reason, "7 + 9" looks difficult for me... Don't you have such combination of numbers you feel a little difficult? For me, the developer of this app, the combinations containing 8 or 9 were difficult. I felt it also hard to calculate the total price of products every time I went shopping. So, I decided to develop this app, considering my own training too, and I actually improved my addition skills to some degree already by testing calculation challenges again and again while I was making the function. I'm sure you'll also improve your own skills as I did! I hope you enjoy the app as kind of a game, as well as it benefits your addition ability. HOW TO USE Seven values are displayed one by one at certain time intervals. Add up those numbers in your mind. STAGES There are 20 stages with a combination of 5 kinds of digits (1 to 5 digits) and 4 intervals (6, 3, 1 and 0.5 seconds). The highest stage is 5 number of digits with 0.5-sec intervals. You will be a real "expert" if you ever reach such a high level! Each stage has its own name. - 1 digit, 6-sec intervals: "Shell" stage - 1 digit, 3-sec intervals: "Prawn" stage - 1 digit, 1-sec intervals: "Turtle" stage and so on... EXPERT MEDALS AND LEVELS You'll get an expert medal if you answer correctly 5 times in a row at a stage. The highest among all the stages where you've obtained medals indicates your current level. How far will you be able to go? Try it now! PRACTICE FUNCTION Unlike your real challenges, you can switch the values by tapping on the forward/back buttons at your own pace. Choose the number of digits that you want to practice, and try as many times as you like, until you get used to it, then you'll see the fruits of the practice at your actual challenge. REVIEW FUNCTION After each challenge, you can review the values you just saw in the challenge. Make use of this function to gain enough confidence to get the right answer within the time limitation. OTHER USEFUL FEATURES - Multiple challengers can be registered, so the whole family can enjoy the app on a single device. - You can set one of preset theme colors, which makes it easier to distinguish your user from others on a device. - Your successful challenge result can be shared on SNS with the screenshot attached. Enjoy your exercises and challenges!