Here is an unordered list of tips that gives you knowledge on the mechanics of the game.

-Aside from maneuverability, look at the wings. the swarm blaster has smaller hitbox than others.

-there are 4 powerups in this game. you lose 1 every time you take damage.
you get and loose from this order:
1) speed boost
2) add 2 more shots
3) you shoots has a wave like projectile
4) A free shield!

-Every time you take damage, the ships staggers and makes you unable to shoot for a time. You also loose a powerup.
However, when you take a power just before you get hit, you take damage but do not loose any powerup.

-in campaign, Take your time to kill the boss. the amount of hp they have is quite insane.

-do not hesitate to read the manual as it give more insight for the game.

Challenges are unlocked as you complete the campaign.
Some challenges are (infinitely) easier than others.
I recommend to finish the campaign before starting any of these challenges.
Here the list from easiest to hardest (in my perspective)

ankoladon swarm <The abyss < asteroid frenzy < raging demons < spearkon invasion < morning stars.

This is by far the easiest.
However it is the last challenge you unlock from campaign.

any ship will suffice. keep swaying from left to right diagonnaly and the purple bullet will do the work for you.
350 kills and your done

The hard part is the time needed for gold : 10 minutes.

the armageddon seems like the correct choice and autofire enabled.
dont hesitate to spam shoot the worms to have more path options.
also there are double walls in some area so go up and down only if you have to.

-you start with full power. try to keep it till the end as there are no power up in this level.

Now the challenge will be a little tougher.

from here on out, autofire should be disable as every shot counts.
-safety first! dot take brash turns and always make sure to have a safe path between the spike rocks.

- I used armagddon for this challenge as I love to move all around.

-be wary when the spike rock take half the screen: there may be one just behind.
aim for the asteroid you know you can handle: they all explode in smaller bits.
you get the gold medal after 500 hits. best of luck

You may be wondering why the first challenge is yet to be seen. You may also be asking yourself why The demons are easier than the spearkon?

even with they're tracking ability, the ships speed is MUCH slower even after 100 kills.

as always, autofire off.
I used the swarm blaster because I mostly use vertical dodge.

like spearkon, they can shoot straight bullet that may damage you. so I recommend to always shoot them will moving. it is both a sure shot and prevents you from being hit.

what I do is play really safely when I dont have the shield and try to get as many kills with shield.
That ensures, you get the most out of the shield I frames.

this challenge is pretty hard, it took me about 10-13 tries to finish it. just dont give up!

It may be the first challenge you unlock but it not the easiest.

there are 2 things that may this challenge... challenging.

1) The more kill you have the faster the ship gets. at 100 already it is hard/impossible to avoid and react to all ships.

2) the ships wings are abnormally large, really hard to avoid hitbox and the purple shot often dont reach them (while of course they can reach you).

I chose the swarm blaster simply because it has a lower hitbox.

my strategy was to capitalise a corner and do small circle around it.
this will try to make a safe spot whenever a plane zooms in.
the 1 flaw of this srategy is that you cannot really dodge if a plane shoots you.

the 2nd srategy is to go in large circles.
this may let you dodge any bullet but its hard to dodge incoming planes.
for this strategy use the ship armaggedon for dodging in all direction.

finaly try to keep powerups as long as possible. essentially the first 1 as the speed upgrade is really good.
I'm not sure how many tries I did but I know i spend most of my time doing this challenge.

go for armageddon for more movement.

I still havent achieved gold on this one, but I know its heavily rng dependent.
1 star may block half of the screen and the next second you get stunlocked to death by hundreds of stars.
there are no power ups in this level.


update :

Most stars are actually aimed towards you! you can avoid most of them by simple circling around.
when a star blocks your view, you can shoot to see if it collides anything.
If it does than most likely you have a star that you better avoid.

A star does not take all the space, you can avoid by a fair marging.

I finished it with the swarmer as the small hitbox is extremly usefull in this challenge.

Thanks for reading and don't hesitate to ask a question or give feedback on this guide.