Q: compulsion Shut the app

Agar.io is not an Apple product, tell it to the developer of the game.

Do you mean the game sometimes quits, or just closes?

Be careful not to touch the Home button while you're playing.

Reset your iPad.

Make sure you have enough free storage space.

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Reset: hold down the Home and Power buttons until you see the Apple logo (10-15 seconds).

Restore your iDevice: https://support.apple.com/en-us/HT204184

If your backup is to iTunes, make sure it's encrypted.