level 4/5 and the final mission +useful weapons
for level 4 or 5 I find it very easy its probably because of the way i do it...I mess around with the weapons/shield/drive to give me max speed when im chasing the pods. Firstly I run into the base and kill everything there I immediately check the map and see 3 pods, I put drive up to 130% and hit the pod at the end of the 3,then the middle pod and then the one at the other end, after I go to the base first I never return I just destroy the pods as quick as possible and it works.
With regards the final mission i go in with a 70 mm and a nuke either shiva or raptor. When the scorpian comes out I leg it then I go back to find him when my shields restore when he lasers me i fire the nuke in his general direction and that gets him stuck in a massive hole! If u have the raptor you can swap the nuke for the fuel air mortar or if you have the Shiva you can bring it in with u, anyway the fuel air mortar will DESTROY the scorpion. when the multiple enemies come out well the shiva has quad primary mounts so quad 70mm takes care of them and you can use your spare secondaries. With Raptor you can swap the nuke for that bazaap weapon
Here's my tip: use your map.
The map will show you where all the enemies are, including the transport pods. Just make a beeline for the pods as soon as you see a window of opportunity. When all the pods are gone, you win, so destroying them as fast as possible will virtually ensure the survival of your base.
That said, I did find several of the levels arbitrarily hard. Running out of ammunition is my leading cause of death even on easy mode. There are two levels I can recall in particular, both on the second planet:
In the first, you're charged with defending a convoy of trucks while they set up a new military base. The enemies you're fighting are all fairly fast and extremely well armed, so just keeping yourself alive is a challenge. I couldn't figure out how to beat that without cheating to get an infinite supply of seeker missiles.
The second problematic level is the last level in the game, in which you need to help some scientists capture an alien portal. Defending the portal is a super-ultimate-uber-megaboss of doom who can take a direct hit with a nuclear missile and remain standing. He also has a ridiculous amount of attack power. The only apparent way to beat him is to have a mech that can run faster than he can turn around and keep circling him, BUT you have to beat him in five minutes or less because the five minute mark is where the scientists come in and if the boss isn't already dead, it will kill them. And when the scientists turn the portal on, it will start spawning an indefinite number of weak units, far more than you could ever destroy quickly no matter what weapons you had. Again, I couldn't win without cheating.
As regards the military base mission It took me almost 2 solid hours to do. I went in with plasmas as 70mm keep runnin out on me, then heat seekers but be careful with them. When you are attacked by enemies you have a planet runner with you, keep him alive as long as possible, save your heat seekers for when your shields are very low or when your enemy is near your essential convoy. The plasma is a very good weapon for attacking planet runners and them fireball aerial units just make sure you hit them the second you see them, you generally leave the weaker flying units till you have all the dangerous enemies killed.
As regards the final level look the latest comment left, you could also use mines or rolling mines are better again for the smaller guys! If you have any other questions just ask me I know pretty much all the missions