How to get the Arrow achievement on Reed 2 for iOS?

I have played Reed 2, the iOS version, and I have gotten 14 out of 15 of the achievements. The last achievement is called "Arrow", and I presume it is unlocked by getting hit by an arrow. However, I have gotten hit by arrows many times, and it still has not unlocked the achievement. What do I have to really do to get the achievement? Is the achievement just glitched? I would be very grateful for some help with this problem.