Very good...
It's a good game! Addictive, loved the fact you added more styles of balloons as the game progressed, and you're forced to use tactics to get a higher score; do you match the colour, or just aim for another, easier balloon? This sort of thing is what makes a game great, and it had a pretty steep challenge to it.
Bad stuff? Well, the sound isn't great, nor is the art, and the gameplay was somewhat repetitive. Personally, I'd have aimed this game for an older audience, as the challenge and the gameplay probably suit that. Maybe add a few extra bits, like bonuses or add-ons, and you'd have a great game.
Still though, good game, fun to play and a welcome distraction. Good job.