Sapper

"Pop 5,000,000 Fortified Bloons or MOAB-Class. Avoid insta-kills or Fort stripping for best results."

- BTD6 description as of Version 25.0

Sapper is an achievement in BTD6. It can be achieved by popping 5,000,000 Fortified Bloons (including Fortified MOAB-class). Using defortifying towers such as Shattering Shells will void contribution to that achievement. On the other hand, use of instakills will not count offspring and only will count the top layer. Earning this achievement will reward 500 and 1 Monkey Knowledge Point.

The table below lists how much each fortified bloon is worth for this achievement if them and their children are popped fully.

Mode Breakdowns
The table below lists the normal bloon rounds (i.e. not Alternate Bloons Rounds or Apopalypse) up to Round 100 which contain fortified bloons, and the total amount contributed to this achievement from that round. This assumes there is no de-fortifying, no regrow, and excludes Golden Bloons. The table below lists the Alternate Bloons Rounds up to Round 100 which contain fortified bloons. As such, the following table lists the expected pop count contributions to this achievement for each game mode if played to completion.

Summary
Maximize popping power by brute-force popping as many Fortified Bloons as possible. Play high rounds and avoid towers and skills that remove fortification (Ezili, Shattering Shells) or towers/abilities that instantly kill (Ezili's MOAB Hex, Monkey Pirate, Navarch of the Seas) to advance progress of this achievement.

Tips

 * This achievement is arguably one of the most tedious to obtain because of the small amount of Fortified Bloons in a casual game.
 * Grinding Freeplay Mode is a must, especially Rounds 101-140 where the Fortified pop count can reach as high as 21,510. See BTD6 Freeplay Mode/Strategies for strategies to obtain high Freeplay Rounds to pop Fortified Bloons.
 * It is not recommended to play extremely high rounds due to the sheer lag and unpredictable MOAB randomization players may face.
 * However, if you set up an extremely powerful defense by the start of the randomized rounds (140), you can leave the game completely AFK and grind out anywhere from 0.5% to 1.5% by simply surviving until round ~250. While this may not be the most time efficient method, it can be extremely useful as it allows you to do other things while your computer/phone runs in the background. See adjacent image for an example lategame defense.Late game sapper defense.png
 * Elite Bloonarius the Inflator can spawn Fortified Bloons starting at Tier 4. It will spew Regrow Fortified Ceramics while taking damage, and spawn Fortified D.D.T.s and B.A.D.s per skull. Tier 5 will spawn 4 Fortified B.A.D.s per skull.
 * Both tiers will provide about 10412 Fortified Bloons. If a player defeats Elite Bloonarius during Round 140, this will provide them with about 31922 Fortfied Bloons in total.
 * Apopalypse is also a good mode to grind for this achievement because the Apopalypse rounds go past round 100 and there are more fortified bloons/moabs.
 * Playing on Alternate Bloons Rounds gives more Fortified Bloons than a regular Hard game, although it is only a slight 776 increase.
 * Playing up to Round 100 actually has 5x the amount of Fortified Bloons one would get compared to Round 80.
 * Do note that ABR will provide random Bloons starting at Round 101+.
 * Don't use towers upgrades that can remove fortified, like Shattering Shells, as the bloons affected won't count to the achievement. It's also not advised to use insta-kills like XXXL Trap, as you miss a lot of pops from the inside of the bloons, especially in MOAB-Class Bloons.

Trivia

 * An equivalent total of 1,694 Impoppable/CHIMPS runs, 233 runs to r140, 4,326 ABR runs, 983 ABR runs to r100, or 26,882 Fortified B.A.D.s has to be popped to obtain the achievement.
 * 50,000 Fortified Bloons make up 1% of the whole achievement.
 * Previous description did not include the extra sentence before Version 25.0, but was added for the sake of ease for how to earn achievement.