Indie developer DodoDroid has released a simple but challenging new arcade game called Sequentia. Like the title suggests, this game is all about tapping on numbers in sequential order. The challenge comes in when you realize that you need to do this as fast as possible.
Players are tasked with tapping on numbers as they appear, from smallest to largest, as fast as you can before the time runs out. There are two different game modes you can attempt to do this in: Time Attack and Survival. In Time Attack, players have a time limit to tapping as many numbers in sequence as they can. Mistakes, however, will result in dinging your time limit, removing a few seconds from it. Survival is essentially the same thing, but one mistake ends the run completely.
This game makes for a decent little time killer where you may have only a couple of minutes to kill. Sequentia is available off of Google Play for free, with no IAPs being included either.