Really good job! I love the sound effects. My first run I didn't realise the darker bubbles in the background weren't deadly, so I thought the game much more difficult than it was haha. I would say you should add some sort of warning to the player that the "bubble-popper" mode is coming to an end, like the player flashes or something. Had lots of fun!
P.S: Next time include the .pck and .exe files together in a .zip please :)