Cool take on the style of game, good graphics and nice arcade feel.
The first medal is 5 points and you won't get it through scoring. Take a guess.
The other three are for score milestones; I believe it's 5k, 10k, and 15k. Got them all on my second attempt.
You might miss the instruction - your multiplier increases from 1 to 5 the farther to the right you are. Start out at 5 and go lower to maintain safety as the game gets faster. This should get you plenty of points. You only have one life, so be careful. There seems to be a small bit of wiggle room on the tunnel-like obstacle sets, though.