First, a few words about how the game works.
In the center of each planet, it is written how much energy it has. Along the perimeter of the planet, there are small stripes, these are shields. Shields work simply as additional energy that cannot be sent to attack. If a clot of enemy energy comes to the planet, then first of all it destroys the shields. Therefore, in order to capture a planet, you need to send enough energy to break through the shields and eat up all the energy on the planet.
For example, most neutral planets have 3 energy and 7 shields. To capture such a planet, you need to send 10 units of energy there.
One interesting nuance follows from this.
Pay attention to what a newly captured neutral planet looks like. It has no shields, because they were destroyed during the capture. It has no energy at all for defense. If at this moment enemy energy comes there, then the enemy gets this planet for free. This doesn't last very long though, because in 4 or 5 seconds the planet will regenerate some energy and restore most of the shields.
Here is the most effective tactic which I always use. If I see that the AI is sending energy to capture a neutral planet adjacent to me, I immediately send my energy there so that it arrives a second later than enemy. This way I get planets for free and greatly delay enemy’s development. The vast majority of levels can be completed simply using this tactic without knowing anything else about the game.
Now let's talk a little about strategy. What I wrote below, by the way, can also be applied to Antiyoy.
The strategy is to gain strength while the other factions are fighting among themselves.
Usually this simply means that you should not interfere in the battle while there is a balance. If one faction is close to completely destroying the other, then it's time to go on the attack. Sometimes there are difficult situations when the player does not have time to accumulate enough strength because one of the factions wins too quickly. In such cases, it makes sense to launch small suicide squads into the faction's rear (where all the economic planets are) to balance the situation and get more time to accumulate power.
Sometimes a player spawns between several factions and because of this experiences pressure from several sides. Instead of fighting on several fronts, it is better to simply step aside and let the factions fight among themselves. The initial territories can be sacrificed in this case.
These two tips should be enough to complete the campaign. Probably the only exception is level 308, even I usually can't complete it on the first try. But it is also beatable, just look for a video on YouTube.