So, it's the morning of my birthday, but I have a little time to play-test my game.
I booted it up and constantly tried to beat my top score, and I did, but I also felt that with each run the player unit (helicopter) behaviour needed tweaking. Currently, it was quite difficult to control. With enough runs, I managed to find a sweet spot for velocity and gravity.
With value tweaks in order, I soon found out there was another issue making it hard to play. The gravity, which I was simply reversing to make the helicopter lift was being added too quickly - reaching a too higher value the longer the mouse was held. It wasn't the speed that this value was changing which was the problem, just how high the value was going. With a few new revisions to my helicopter class, I found that simply constraining the gravity, plus or negative, to a value of five made a huge difference to the playability of my game.
Expect some third party testing tomorrow!