Complete the following levels by performing the corresponding strategies:
Level 13 To easily complete level 13, swim in the water and allow the ants to surround you. You will eventually be able to walk on top of them and shoot them. Level 25 Bring any desired weapon and C70, which starts appearing on the Hardest difficulty around level 36; try farming level 40 on Hardest. When the level begins, start dropping C70 off the sides of the path and detonating them. The C70 has a 40 meter blast radius; be careful not to be within the blast radius. You should be able to get the enemy numbers down to about 20 by doing this. Then, just mop up the remnants. Note: This also works on Infiltration 1. Level 21 This level will introduce you to the big brothers of the black ants: the red ants. These ants have an impressive amount of armor and attack in big waves, allowing them to survive your hail of fire long enough to get close and hurt you badly. Simply running and gunning won't cut it. Instead, equip a rocket launcher with a large blast radius (the Goliath or one of the later model Stingrays work great) and a sentry gun of some type. Lay down the sentry guns and bombard the enemies with the rocket launcher as they approach. As soon as the ants get in range, activate the guns. This will slow downthe opponents' advance considerably as the front line is constantly hit by the sentries. Take this oppotunity to pick off the ones that break through your wall of fire. A second group will spawn behind your starting location so make sure to reload your sentry guns before the first group is defeated. Use this strategy on all three waves to succeed.
Level 27 In this level, you are stuck in the middle of a network of tunnels with enemies attacking you from all directions. You have three allies, all of whom have nothing but close ranged flamethrowers. To survive, first grab an assault rifle and some sentry guns. Start the level by dropping the sentry guns as fast as you can, activating them as they deploy, and then run down one of the tunnels. This will force enemies that are not in that particular corridor to come through the center area to get to you.The sentry guns will be doing most of the work for you as you eliminate the group in the tunnel ahead of you. You should have time to find a place to hunker down in one of the corridors. If you can find a location with only two entrances that has a nearby bend (to reduce some enemy fire), remain there and take on incoming enemies while reloading your sentry guns. Once reloaded, you have the choice of either using the sentry guns for extra firepower to take out the remaining enemies, o breaking through into the center and repeating the process. Level 32 This level pits you and a group of snipers against a massive army of spiders. The battle takes place in the middle of a ruined city and thus the rubble makes it incredibly difficult to get a shot on the encroaching horde before it reaches you. To solve this problem, take a close combat weapon like a shotgun or assault rifle for any close up work, and an MLRA.Since the rubble blocks most of your shots, aim upwards with the MLRA and sweep from side to side to lock on to different spiders. This will create an aerial bombardment against the spiders which they can't defend from.
Level 33 Here you must confront the spider fortress. Use a sniper rifle or rocket launcher to take out the UFO carriers while using any weapon to take out the ants and Gunships that will be attacking during the onslaught. A good shotgun is recommended. First, completely ignore your troops and allow them to rush into combat while you move to the left of the starting point until you are almost at the western edge of the stage. From here, kill any enemies that are coming in and attack the first of the carriers. Attacking the carrier will make any enemies it has deployed attack you, but you won't have to deal with the enemies that are under the other carrier. At some point, the fortress will start firing cannons and moving. Avoid it by moving north or south as needed to keep your distance. As long as you do so, the lasers will never come close enough to be a threat, leaving you to simply take out the couple of UFO carriers. Let the fortress go its own way s ince you won't be taking it down until the next level.
Level 9 Here you'll face a new type of enemy, the Walking Arms, or Hectors. These strong mobile weapon platforms can be outfitted with a variety of oversized attachments on each arm to adapt to their enemies. The Walking Arms will start out far from the shore but will be move closer as it rains down destruction on the group of troops gathered there. A big group of gunships will also have to be taken care of well. The Walking Arm's weakness is that their height makes them very unstable and rapid firing weapons can easily throw off their aim. As a result, closing the distance with an assault rifle, preferably an RA model, is pretty easy. This will also cut down on incoming damage by a huge amount while allowing your supporting troops to damage it significantly. As for the gunships, there are two ways of eliminating them while maintaining focus on the more dangerous Walking Arms. The first is to use a missile launcher with a fast missile (MLRAs or Emeralds work well) and firing off a couple shots at the swarm of Gunships while you focus on the Walking Arms. This will let you take them out every time you get a spare moment and reduce the amount of enemies firing upon your troops.The other method is to use groups of sentry guns, preferably rapid firing ones such as the ZERA. This will let you concentrate on the Walking Arms while the guns eliminate the Gunships.