I was happy to fork out the small amount of cash being asked for the full version of this game. Really well thought out and makes a change to have a TD with a story and upgradeable characters.
The reason you're levels have dropped is because the exp needed to level up has been increased. You still have the same amount of exp you had before but at a lower level to balance things out. The energy needed and exp rate per mission has also been altered.
I too have gone from level 50 to level 17. But remember this game is still new and being tweaked so it is far too easy to complain about it, when there is a lot of work to be done to make this game better for us to play.
Really cool original game, brought it after playing the first level, a bargain at £3.30. Is there any way of downloading the game or playing it in full screen ?
 "Defender's Quest (lengthy!) Demo"){kind=icon}
 "Pingy the Ping Idle RPG"){kind=icon}
 "Epic War Saga"){kind=icon}
 "Henry Stickmin : Escaping the Prison"){kind=icon}