Tunnels/Strategies

Tunnels is an Expert track in which the bloons constantly enter tunnels, giving them temporary protection, bar M.O.A.B. Class Bloons, which will be visible moving over the tunnel.

Tips

 * Dart Monkeys (4/2 upgrade) are considered effective in the track due to some straight lines seen on it and their cost efficiency.
 * Glue Monkeys (2/2 upgrade) are extremely useful considering that the glue will continue popping the bloons through the tunnels. (2/3 upgrade) would be even more useful, as (2/2 upgrade) will not get all bloons.
 * Ice Towers (in 4/2 or 2/4 upgrade) are useful in this track especially when the bloons reached the next tunnel.
 * 4/1 or 4/2 Ninjas Monkeys are very effective on the straight parts.
 * Keep in mind that this track is quite long although about half of it is covered; thus Spike Factories are quite essential for this track.
 * Monkey Apprentices are highly useful on this track, especially upgraded to 2/2 or farther. The lightning can arc across multiple paths.
 * A really useful strategy is to use 2/3 spike factories wove the tunnels; even though it seems like all the spikes aren't landing on the track, it damages MOAB-class bloons. The main problem with 2/3 spike factories is that spikes which could be used towards MOAB-class bloons will be used up by smaller bloons.
 * It is possible to beat this map with just Dartling Guns and Juggernauts. It is also possible to beat it with only Dart Monkeys (and Villages and Farms) in Hard Mode.

Spamming 2/0 and 3/0 Engineers in Mobile along with a few 2/2 Spike Factories seems to work well.

Flash Strategy
Hello, this strategy might work on mobile/steam however I am not sure. You can play the flash version via Flashpoint. This strategy worked for me on hard NAPS NLL. Don't forget to place road spikes when you need to.

Start with 3 dart monkeys around the map, each covering two sections or tunnels of the track.

Quickly add a fourth.

Then, add a sniper and set to strong.

Upgrade two of your dart monkeys to long range.

Get a farm and upgrade to 1/0.

Get a spike factory and place at the end.

Add a glue gunner and quickly get 2/1 upgrades.

Set glue gunner to strong.

Add another farm if you can, also upgrading to 1/0.

Upgrade one or two of your dart monkeys to 4/2

Upgrade your spike factory to 2/2, 1/2 or 3/2 if you need.

Add one or two more farms depending on how you are going, always upgrade new farms to 1/0.

If you can, upgrade one of your farms to a plantation.

Now try to save up for a super monkey.

Sell all insignificant towers (unupgraded dart monkeys and sniper monkey)

Slowly upgrade your super monkey to a plasma robo monkey.

Upgrade your farms like a lot, most to 3/0. (you can do this before saving for super monkey)

Add a hut next to your robo monkey, set to 2/2 upgrades.

Upgrade your farms to 4/2 when you can and spam plasma robo monkeys.

If you really want, you can also get moab maulers.

This should lead to a win, if not, maybe leave in the comments how and at what stage you lost.