It Came from the Desert features (somewhat) non-linear game play. You have a certain level of control over what events you see and which mini-games you play. Unfortunately it's very easy to get sidetracked and wind up in a position where it's impossible to finish. The first time I played through I made every effort to avoid the tunnels because they were a pain, turns out they're extremely mandatory. To win the game there are several key tasks you need to accomplish:
The main objective of Day 1 is to get as deep into the ant tunnels as possible. Along the way there are a few encounters to advance the storyline.
The day begins in the Lab. Doc asks you to go out to Borax and re-enable his radiation sensor grid.
Go to the Borax Saloon and choose Strength.
You'll be introduced to the trainer. You'll need to visit him again on Day 2 to learn the forward flip.
After visiting the trainer you'll fall into the ant mine tunnels. Get as far as you possibly can. To win the game you need to get down to the third set of tunnels and see the force field protecting the queen. The first set of tunnels look like a mine. Keep going through until you reach the elevator to the next tunnel depth.
The next stage is a dark blue cave. Even without learning the forward flip you should still be able to reach this level. Luckily, if you're captured you will be returned to the deepest level you reached next time you re-enter.
It will be tough to get to the third, red, level of the tunnels. At this point the ants and zombies are moving quickly and often seem to come out of nowhere.
Keep going until you see the force field.
Once you see it let yourself get captured.
If you don't make it this far on Day 1 that's OK, you will have several chances on Day 2 and Day 3.
Next go to Lud's Ammo.
On the way you'll be stopped by the Sheriff and have a strange dialog.
Your first meeting with Lud is a little rough but as the game advances he comes over to your side.
Return to the Lab, you should see a total of three sequences with Doc and receive the two-way communicators.
If you made it down to the force field then there's a fourth dialog where he tells you to find three transponders. I actually have no idea where or how you find these, maybe by beating mini-games? By Day 5 Doc somehow has them so it doesn't matter.
You automatically return home for a fight with your parents.
After that, go to Foundry. There will be a brief dialog followed by an easy shooting game. When that's done visit whichever destination you like to wrap-up the first day.
If you did not reach the force field on Day 1 then that needs to be the focus of Day 2. At the end of the day you need to visit the Borax Saloon to learn the forward flip.
Day 2 begins with Doc explaining his theory about the ant mind.
Go to the Mine Shaft if you need to advance further in the tunnels. If you've already made it down to the force field then go wherever.
After visiting a couple of places you'll automatically hit an overhead battle.
If you advanced to the force field on the last tunnel run then return to the Lab.
Otherwise, go talk to the Sheriff then visit the Power Plant.
At the Power Plant you'll have a run-in with one of the workers then be given a choice to run. Choose Don't Run of course.
Win the ensuing overhead battle.
You'll automatically go back to the Lab for another dialog with Doc.
Next you'll automatically return home. Look at the TV, this sort of helps the ending make sense when you get there.
Go back to Borax.
Return to the Saloon and select Strength to learn the forward flip. This will make it much, much easier to get through the tunnels if you haven't made it to the force field yet.
There are two goals for Day 3 - get to the force field in the tunnels if you haven't and give Sonny one of the two-way communicators you received from Doc.
Day 3 begins at home.
Go to Sonny's first.
You'll give him one of the two-way communicators.
Doc informs you that there's a tunnel under the lab which you are automatically sent to. If you've already made it down to the force field then just get captured right away and be done with it.
After that you return home, look at the TV if you want to but it's not required.
If you made it to the force field on the last tunnel run then go back to the Lab. Otherwise go to Prissy's for a dialog about her sister acting weird.
Day 4 is your last chance to reach the force field. If you've already been there then Day 4 is pretty light.
After the fight Doc informs you that his reflector was stolen.
Go to Sonny's first. After that select the Foundry or Mine to enter tunnels.
After that go to Lud's Ammo.
After the dialog with Lud go to the Lab if you finally reached the force field, otherwise go to either the Borax Saloon or Channel 14 to waste time.
Back at home you can watch TV or listen to the radio, doesn't matter what you choose here.
Next go back to the Lab.
At the lab you'll see a nice map illustrating the areas to protect.
Day 5 kicks-off the home stretch of the game. By the end of the day you should have the force field protecting the queen disabled. If you're really good, you can even finish her off today.
Doc will now give an explanation of ants' plan.
After all that you return home for a shooting game.
Head over to the Lab. Doc is in some trouble. There's an overhead
battle you should be able to win easily. The only thing to watch out for
is that a new hole opens mid-battle near the top-right one, don't be standing
too close when it does.
After the battle you find a note from Doc. And, if you've done everything right, you will receive message from Doc that the force field has been disabled.
Go to the Atomic Plant to enter the tunnels and hopefully finish the game.
Advance to the queen's lair and kill her.
If you didn't win the game then Day 5 ends with a difficult shooting game.
If the force field hasn't been disabled yet then go to Sonny's first thing on Day 6. Later in the day you'll receive a message from him indicating that he's disabled the field. Otherwise just head over to the Atomic Plant for another shot at the queen.
And that's it for the walkthrough - just keep going to locations with tunnel access until you kill the queen, anything else is simply a distraction. The ants will nuke the city if you take too long (Day 8 for sure unless you lose several mini-games then it can happen almost any time).