DoctorMuffins: "On The 100, I can’t juggle for very long. The sell time becomes longer as the game goes on. How do I deal with that?"
Sell them immediattely, yes. Also, if you have *3* paths to use for your juggling you can bunch the enemies up.
To actually beat the 100 (not just do the challenge) you have to use lots of anti-air and snap towers. I used 1 quake tower, and all the rest was walls, snaps, boosts, and anti-air.
If you don't like juggling, just play the 'no sell' challenge.
As for the 100 - it's possible to get 12,000 on it without juggling, but you can only complete the 100 (with lives remaining) using juggling.