User blog comment:Anomalous13/Bloons Wiki News - June 3, 2012/@comment-1313357-20120601023212

The BTD1 and 5 is the hardest? LOOOOOOOL! Those who vtaram such option is judged because the price of monkeys (in BTD1 is more expensive to buy the basic version) or the tracks and level balloon (the most extreme and the castle are tracks harder than any other track ever created, the minus the free version, the ZOMG needless to comment).

In dificudade level, the BTD2 is in my rank, the second is BTD3 the BTD1 third, and fourth is the BTD4 BTD5 is easier, to have several varieties of towers and strategies to complete the game, even in hard mode.