Launching an all-out attack against the aliens is always tempting. And it’s a lot of fun as well, as you charge at the aliens with all your troops and all your weapons. But it’s not always that easy as it sounds, and it would actually be wiser to go slow and steady and make sure your troops are together. While this takes less time, it gives you a better chance of victory, and leaves your troops less vulnerable to enemy attacks; using an all-out strategy often leads to individual troops being ganged up on by the enemy.
Now, you may also have thought that the best way to deal with the aliens is to stand your ground and not do anything unless they strike first. That’s only going to lead to a lot of boredom, as the aliens won’t move if you don’t.
Having a good and smart formation always helps in improving your chances of victory. Your melee attackers/heavy troops should be in the front line, followed by your ranged fighters right behind them. Those who rely on speed and stealth don’t have high attack stats or a lot of health points, but they’ll be your best offense against enemy ranged troops. As for your range troops, they make for a great way to deal with alien heavy troops quickly and efficiently.
If the aliens are trying to use their strength in numbers on you, it’s best to focus on one side individually, usually the toughest, before you take care of the other sides.
You can potentially earn a maximum three relics per stage, and if you aren’t able to get all of them right off the bat, you can always “grind,” or replay a previously-completed stage, once you’ve unlocked more troops and completed other stages. New troops can be used in any stage, including those you’ve completed in the past.
Conversely, if your goal is to unlock as many troops as possible, you wouldn’t want to grind old levels. Instead, try to beat each stage and move on to the next – one stage unlocked is equivalent to one new troop unlocked.