Mothraya - Cossack 1 boss fight

Mothraya (usually nicknamed Moth) is the first boss you encounter in the Castle Stages

It's battle takes place on a two-layer pipe bridge. Mothraya can move left and right on the upper screen, attacking every 2 seconds with energy shots. It's main move is a spike-tipped "proboscis" with two attacks—one sudden dip to the floor and another where it slams down after a brief pause, breaking part of the bridge, which is usually a pretty favorable pattern in speedruns making it easier to get shots in despite the lag.

The weakness is Ring Boomerang which combined with the one pixel hitbox of Mothraya makes the fight significantly harder than it looks to do properly

Strategy

The plan is to keep a rhythm with the up and down movement while also baiting Mothraya's shots to go downwards as we jump upwards.

In order to get the shots in, we need Mothraya to go down as Mega Man goes up, that way when Mega Man reach top height, you should be aligned correctly to shot the Ring Boomerang properly.

To do so, we need to walk until we reach this point from which afterwards you want to do a full jump and release the shot as you reach max height

You can use those 2 lines as a cue, here we want to jump before the first line.

Afterwards, Moth will go up as you are falling back down, so then you want to wait a bit that Moth goes back down and do the same thing. Watch Fight example to have a good understanding of the timing needed.

You can speed up this fight by a few frames by jumping a bit earlier in between the small left pipe and the first line

You may encounter various problems when trying to do this fight fast:

• If you tend to move around a bit too much when you throw a Ring Boomerang it can cause issues when coming back to you causing you to generally loose a cycle 
• Trying to go to fast can make you miss in case Moth dives down quickly instead of doing it's regular movement
• Going out of your rhythm can make the fight harder as you can get pushed to the left side very quickly
• Dodging the bullet can be harder if you jump too fast

Fight example

It's worth noting that the wings of the boss doesnt have an hitbox so you can go into them. Only the square is.

If you miss a shot don't go out of your rhythm, if you try shooting right away you will miss. Wait that Moth goes back down again just as if you didnt missed the shot