Slick Skate

 is the 49th level in Bloons 2 Christmas Pack. It can be found by clicking on the Christmas tree's star.

Solution
Bounce first dart onto the Green Bloons, and let that dart also hit the Bomb Bloons. Bounce second dart to hit the bottom-left Spiky Bloons, which will then wipe out the bottom stuff. Throw the third dart onto top. Throw fourth dart into a bunch of Ice Bloons.