Spiked mines explode violently when they lose all their spikes.
~ BTD6 Official Description
Spiked Mines is the 4th upgrade of Path 1 for the Spike Factory in BTD6. It allows its depleted spike ball piles to create powerful explosions, dealing 10 damage each to up to 40 bloons, alongside a powerful napalm that deals one damage per 2.0s for 6 seconds. The blast radius of the explosion is 19, around the size of the explosions from Bigger Bombs. Explosions deal double damage if the spiked mines automatically expire rather than if the spiked mines are fully depleted. Each spike also deals +6 damage versus Ceramics instead of +3, for 8 damage versus Ceramics.
The main power comes from the heavy explosives that spawn from emptied spiked mines. These deal 10 damage each. The main use for the Spiked Mines (specifically a 4-2-0 Spiked Mines, for the attack speed increase) in most games is to beat difficult pre-Round 81 bloon rush rounds with ease. Compared to other Spike Factory upgrades, it is surprisingly good at beating Regrow Bloons (with the exception of Regrow Blacks and Regrow Zebras), and it cleans up densely grouped bloons very effectively, unlike its previous upgrade Spiked Balls.
Use this if grouped bloons are a serious issue. Spiked Mines is effective at wiping out dense bloon rounds such as Rounds 63 and 78, and it can also be used to counter Regrow Bloons if the Regrows do not overmultiply.
Similarly to Ground Zero base bomb attacks, Spiked Mines explosions are highly potent at large-scale damage, but they heavily struggle against dense groups of Blacks or Zebras due to the explosion immunities of those bloon types.
It is better off using a 4-2-0 Spiked Mines over a 4-0-2 Spiked Mines in most situations. Projectile lifespan increase and increased range from Long Reach actually worsens the Spiked Mines performance overall, and the special target priorities plus start-of-round attack speed boosts from Smart Spikes is generally inferior.
Compared to Spiked Balls armies, Spiked Mines is more cost-efficient at overall DPS on single-lane maps, although Spiked Mines has the disadvantage of no full discounts from Monkey Commerce.
Because the mine explosions can't damage DDTs without MIB or similar, Spiked Mines may struggle versus DDTs.
Spiked Mines had been buffed overall throughout updates in this game. Substantial damage buffs for the explosions, added price reductions, an increased blast radius, and several Spiked Balls inherited buffs have made the Spiked Mines upgrade stronger in mid-game settings, more specifically versus mid-game grouped bloons.
Spiked Mines costs less ($14,000 → $12,000)
Spiked Mines explosion deals more damage (4 → 5)
Spiked Mines explosion deals more damage (5 → 10)
Spiked Mines spikes now deal +1 damage to all bloon types.
Spiked Mines explosion radius increased (15 → 19)
Base projectile lifespan reduced from 70s to 50s
Spiked Mines spikes now deals extra Ceramic damage (+3 → +6)
The Spiked Mines cost is the same as the old buff in BTDB Mobile.
The napalm damage-over-time for Spiked Mines is the same as BTD5's Burny Stuff effect, which deals 1 damage per 2.0s for 6.0 seconds.
Spiked Mines received a buff to its spike damage versus Ceramics in Version 22.0 in order to give it more potential versus greater numbers of Spiked Balls, according to Ninja Kiwi's Version 22.0 patch notes.