The problem is this game is too much luck. And you might say it's skill but, I'm sorry it's mostly just luck to be honest.
There are many combinations where it is not possible not to lose a life. Get three such combos without picking up any lives? Game over. Heck, even going for that extra life right from the start, didn't miss a shot on that wall, still oftentimes not enough to break the wall, lose a life gain a life, then lose a second life on the next wall, net loss of 1 life.
So high score, and thereby medals, become a factor of almost entirely luck.
The thing if you make randomly generated level type games is making sure any combination it could give you, including any subsequent combination it would give you after that (chaining) are actually all possible. And I really don't believe they are, here.
Also it needs to play the same on all browsers, so if it's actually meant to play slower than it does for me or if he's meant to shoot faster than he does for me, that kind of thing would make a huge difference. And there would really be no way for me to know and for all I know it plays as it's supposed to, just entirely luck you don't get some impossible combination.