In BTD5 (as well as BTD5 Mobile), all of the rounds are the same in every game (except in Mastery Mode as well as Impoppable Mode's Round 85). So I am thinking of a special Rounds To Watch For list, which displays all of the notable rounds, whether be problematically difficult or not, throughout the game until Round 86+.
My list is this, so far, with very difficult rounds to watch for in bold:
- Round 1 - Starts of Reds
- Round 3 - Starts of Blues
- Round 6 - Starts of Greens
- Round 11 - Starts of Yellows
- Round 15 - Starts of Pinks
- Round 17 - Starts of Regrows, starting with 8 Regrow Yellows.
- Round 20 and 22 - Starts of Black Bloons and White Bloons, respectively.
- Round 24 - Starts of Camos. One Green Camo Bloon.
- Round 26 - Starts of Zebras
- Round 28 - Starts of Leads
- Round 31 - Zebras and Regrow Zebras incoming.
- Round 33 - Second occurrence of Camos.
- Round 35 - Starts of Rainbows
- Round 37 - Camo Whites is the third occurrence of Camos.
- Round 40 - Starts of Ceramics.
- Round 42 - Regen Rainbows and Camo Rainbows. Fourth occurrence of Camos.
- Round 46 - Starts of MOAB. Single MOAB.
- Round 50 - One MOAB then another MOAB.
- Round 59 - Camo Lead round.
- Round 60 - Starts of BFBs. Single BFB
- Round 62 - Several Camo Regen Rainbows.
- Round 63 - Massive Ceramic rushes plus Lead rushes
- Round 65 - two BFBs behind each other.
- Round 70 - Many Camo Rainbows
- Round 75 - Final Lead round.
- Round 76 - Giant Regrow Ceramic Rush
- Round 78 - Huge Grouped Ceramics, plus a BFB, plus a huge Grouped Camo Ceramics.
- Round 79 - Many Rainbow Regrows within multiple spaced BFBs.
- Round 82 - Many Camo Regen Rainbows within multiple spaced BFBs.
- Round 83 and 84 - Final difficult MOAB-class rush rounds
- Round 85 - ZOMG (5 in Impoppable Difficulty).