This is a classic "Number Guessing Game" created by Tanmay Bakshi. This app generates a random number which you must guess correctly to win. You get unlimited tries. When you get an answer wrong, the app will tell you if your number is too big, too small and also tell you the number of tries you made. If you get it right, it will tell you that you are right and also tell you how many tries it took you to win.
This works on the iPhone 5, 5c, 5s, 6, 6+ and the Apple Watch, as well.
Any time, you can switch and continue your game from Apple Watch to iPhone or vice versa. This is done by clicking the "Continue on Watch" button on your iPhone, or force-tapping and then clicking "Continue on iPhone" on your Watch.
Hope you learn and have fun,
TANMAY BAKSHI