Xenos

Since they can have multiple denominations I will call them (in the order given in the game): "saber" and "dash", "hurricane" and "throw", "crusher" and "shockwave", "slicer" and "graviton orb (or orb)", "megatron" and "whirlwind".

1) The saber has very short range and good damage. Its special attack is the only one allowing a new movement but hits very few enemies.
You are invincible during the dash which allows a trick: if you dash into the cleanser's ray, you will be violently pushed to the right.

2) The hurricane has a good range and damage. Its special attack shields you very little compared to others and allows melee and big robots to touch you easily, so you better focus on avoiding them if you throw your weapon.
If you fly away from your weapon, it will come back at high speed but with enough energy and space to move, it will never reach you.
This is possible in the survival area.
Unfortunately, the only way to make damage is then to ram into the robots, with no weapon in hand, but still it is fun.
Also, unlike the megatron, the hurricane's color will remain the same so it allows you to keep it in the red for a lot of time.

3) The crusher has a very short range but possibly the most damage (maybe it's the megatron, I'd need more experiments).
It's special attack is just like they say, devastating but needs to be charged; it creates shortly a small safezone. Can be used to destroy clumps of turtloids or bug robots.

4) The slicer has the most damage and the weakest damage. It often reaches multiple robots at once and is great to deal with bees or basic robots. The graviton orb creates a safezone which lasts for several seconds but deals near to zero damage: only the weakest robots and mines will get destroyed, but all will be paralysed.
Beware: when the orb disappears, sword and big robots will still be in a slicing pattern if they already were then they got caught in the orb (which happens frequently because they fly towards you).
Robots keep being pushed by your attacks and can escape the orb this way.
Also, the orb is inactive (I mean it is only an image and deals no more damage) as soon as it starts fading.
You can launch a graviton orb and stay behind, watching the robots jump into it.

5) The megatron has good reach and great damage. Its whirlwind is best used against clumps of lizards or sword robots; it makes you invincible as long as you are spinning thus nullifying any counter-attack and attacks more robots in range than with a basic attack.

I'll call them (by order of HP): "mine", "basic robot", "bee", "lizard", "sword robot", "big (or huge) robot", "turtloid", "boss".
Though there are obvious scientific issues about that I'll talk about "plasma balls", "lasers" (the purple lines) which can be "straight" and "curved" and "boomerangs"; their weaponry also includes "swords", "big (or huge) swords" and "missiles".

Mines get destroyed in one hit of any special attack. I'm not sure but I don't think they count for your number of targets per attack (with the dash and whirlwind).
They are faster than you in a line but they turn quite slowly.
They deal a LOT of damage: five of them are enough to kill you with the barrier wing.

Basic robots have low health and speed. They will hover around you, trying to escape if you approach. They fire a plasma ball every few seconds, sometimes drop cubes of energy and rarely a small sphere of energy. The slicer is great against them, but anyway they are more useful than annoying: you can use them to gather enough energy for your first special attack.

Bees have the same behavior as basic robots but their much higher speed makes them surround you quickly. They fire three consecutives straight lasers. In group, they can pack a punch if you don't dodge any attack. The fastest way to catch them is to wait for them at their warping point. You can ignore them if there are bigger threats and you will randomly chop them up with time. They sometimes drop cubes of energy and rarely a small sphere of energy.
Once again, the slicer is by far the easiest way to deal with these.

Lizards have the same behavior and speed as basic robots. They fire boomerangs and drop cubes and uncommonly small spheres of energy.
Anything works fine with them and it is very unlikely that their attacks can damage you significantly. They can absorb your hits while sword or big robots charge you though.

Sword robots have two patterns which they alternate through:
They will fire three straight lasers in a close angle and hover around or charge their sword (it glows) and fly towards you.
If only one or two charge at once, you will kick them away, but if dozens get into contact most of them will deal you a lot af damage.
If you get cut, there is a very brief interval during which you can move but not attack; you ought to flee if it happens.
They drop cubes of energy or small spheres sometimes.

Huge robots alternate between two patterns:
They will fire three curved lasers all around them in about twenty directions (in the shape of a spiral) or charge their sword and fly towards you. You don't want to get cut even once by them. If you ram into them, always use a special attack in some way to avoid their sword. They often drop small spheres of energy and sometimes cubes.

Turtloids are very slow but will try to chase you anyway. They alternate between firing a salvo of plasma balls and missiles.
The missiles are fast but turn slowly. Always dodge or destroy them because they hurt a lot. The plasma balls can be devastating in close contact. They drop small spheres of energy and rarely cubes.
For those two big enemies, you can keep the initiative by attacking constantly, never allowing them to breath if they are not too many.

Bosses have simple patterns and call in reinforcements mid-life. They have a lot of life, aren't disturbed by your hits and often drop cubes of energy.

I'll talk only about minefields, cleanser's missions, bosses, secret area and survival.

There are two ways (as far as I know) to pass minefields: you can get close, activate one or two mines and immediately retreat in the whole area; in a big room, you can use the fact that mines automatically explode after some time (out of fuel?) and fly in big circles until the area is clean. This is not very fun and contrasts with the fast-paced gameplay.
You can also rush in, as says Asterus: go fast enough to crash the mines in the walls. You can use special attacks to destroy a bunch of mines about to reach you. This can be tough and requires several tries, as well as a knowledge of the map.

In cleanser's missions, you should utilize the fact that the cleanser goes faster when you are far from it. It slows greatly when you stay close to it. Try to stay on the left if there is a vertical corridor. Also if you dash into the death ray, you will be violently projected.

Against bosses, you can go slowly, learning its patterns, dodging, hitting once, going back,etc... You probably want to use the slicer then.
Or you may try to rush at it, gathering enough energy to finish quickly. It's more risky. You should then use the crusher or the megatron's high damage.

The secret area is extremely hard to beat. If you go slowly through the minefields, you won't have any energy to face the next wave of robots. I think it's much easier to rush through the mines, use a whirlwind to make them crash, and go fighting with a bit of energy to start with a special attack.
The accumulation of turtloids makes it suicide to go without a special attack. You may also wait for them to launch their bullets, destroy small and isolated robots to get enough energy and go inside the battle. The graviton orb the shockwave or the whirlwind are almost necessary (for their shielding). I dare anyone to beat this mission with the saber or the hurricane.
In the last fight zone, DON'T try to get the generators quickly, you could lose all your work to get there.
Forget about killing the turtloids inside using the hurricane or the graviton orb. They just don't deal enough damage. You can either ignore them and dodge their attacks while hitting the generators or destroy them using the shockwave. The megatron with enough energy can also reach them (and so does the slicer).
Beware not to get killed by them at the very end, it's really frustrationg.

For the survival, the megatron is not available and there are so many enemies that you will almost certainly use the slicer. It can be funny to train throwing the hurricane and never catching it again, this is the only room large enough to do it.