@DremTheSilent: This was one of the highest quality flash games back in 2009. Moore's Law about doubling computer power every 5 years also applies to the software, which also doubles every 5 years.
FYI, I was able to complete today's Daily Challenge by beating only through Round 46 instead of Round 50. It might have been a bug for me, but it might be the same for everyone that they only need to beat Round 46.
In case anyone is still stuck with Jan. 2nds Daily Challenge, start with a Spike Factory to the left of the end of the track. Then place a Glue Gunner above the beginning of the track such that it can also hit Bloons that come around the top to do a U-turn at the windmill. Then place a 2nd Spike Factory in the middle of the U-turn at the beginning of the track. Then for the 4th tower, place a Monkey Ace in the center of the course. First get the Spike Factories 1|0, then upgrade Glue Gunner to 2|3, then Spike Factories to 2|3, and then Monkey Ace to 2|3, with Special Ability upgrades being last. You shouldn't lose any lives, and you won't even need to place a 5th tower.
Translation of jrs51's comment: "This game is pure action all the time, is very good indeed, I recommend this game". This statement is true, and for a game made 5 years ago in 2008, it's not bad.
@Lord_Jragon: Since they are simple note, there is absolutely nothing wrong with using them. In fact, back when game were on floppy disks, those were the ONLY sounds the games made.
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