Enjoyable but ripping you off

This game is very enjoyable and addictive, with one VERY BAD FEATURE.
It has something called "energy". You are given a certain amount of energy in the beginning. As you play, the energy automatically decreases. By the time it reaches zero, you CAN NO LONGER PLAY.

There are only two ways to get the energy back: 1) wait for a long, indefinite time, or 2) buy it.

I dont think thats fair for the customer. The developer should develop another way to get money (by selling points, for example). To the best of my knowledge, the developer has also been silent about that energy thing. The chance is that they cant justify why it has to be there.

Cepandr about Airport Madness Challenge