Sigma 2 is heavy on RNG, light on execution, for the most part. There are 6 possible gap jumps you can go for, beyond that there isn't any particularly tricky execution.
You can open sigma 2 in a few ways. The easiest way is to just use c.sting on the second revolving platform, you can make it to the door in one charge. You can also try a slightly different approach to the platforms, to avoid wallkicking the left side of the second platform. Wait for the first platform to rise a little bit before jumping, then dash off the right side of the second platform and do a dash wallkick to get across.
If you want to conserve c.sting, you can also use rolling shield and tornado to get through the enemies, and also get a partial charge going into the penguin refight.
Penguin refight Edit
Just use fire the whole time, you have 3 attempts at charge shots before you need to conserve ammo. When you aren't charging, just lightly tap shoot when he's vulnerable and don't fire at all otherwise. If you've hit penguin with the charged shot 3-4 times in the first 2 charges, charge up a third time. Hitting penguin with 5 charged shots reduces the number of total hits again, so take the chance if given the opportunity. Otherwise, just try to get 2 charged hits in.
Post-penguin hallway, up to Rangda fight Edit
Avoid killing the first mech suit guy in the next hallway. Killing him causes more to spawn farther down the hallway, and they're spawned in the suits so they can't be avoided nearly as easily. Use either rolling shield or buster shots to kill the miners in your way. The buster is safer, to avoid drops, but rolling shield is easy, and if you make the right movements you can dash underneath the drops and avoid them anyway. After the last miner, switch to torpedo and fire two to kill the flying enemies that drop down toward you, you might need to practice the timing on the shots a little so they die quickly. When they're dead, fire another torpedo and hold a charge, the torpedo will kill the mech suit guy before he jumps into his mech so you can do the next climb.
If you want to save about a second, do gap jumps on each ladder. The first, second, and last gap jumps should be 7 pixel wallkick gap jumps. The third should just be done with a doublekick.
Eagle refight is identical to the first fight, just use a dash shot then c.sting.
After eagle, charge c.sting and use it before you're going to bonk into something. Do a doublekick on the left wall, then another doublekick on the right wall. They give you just enough height to reach the next platforms smoothly, and saves a little time from doing a larger jump. You can technically gap jump both of the ladders in the last climb, the first one isn't too tough, but the second isn't really worth it, it's a short ladder and the area is laggy.
Rangda Bangda fight Edit
There are 4 different behaviors the eyes can do.
- Green eyes: These are annoying to get, if you position yourself up near an eye as it would open and it turns out to be green, you can get 2 hits on it before it closes again. Otherwise, you're stuck with only hitting it once, especially if it opens on the far side of the room.
- Blue eyes: These are good to get early in the fight, a far side blue guy will cross the length of the room, wait, then go back, giving you enough time to kill it outright. You can get multiple hits on a same-side blue eye too. After killing the nose, be careful about them though, as bonks deal lots of damage.
- Red eyes: There are two types of red eyes, one stays in position and shoots a trio of shots repeatedly. Depending on how many it fires, you can kill the eye outright, or just get a few hits in.
- The other kind of red eye will fire 2 shots and move similarly to the blue eye.
The nose wastes a lot of time if you miss one-cycling it (unless you killed the eyes first), because the walls move again. Get around eye-level with the nose as it gets ready to move and fire a shot early and immediately wallkick. When you reach the wall again, do a dash wallkick. Look at which direction the nose is going, if it's going toward you, stay on the same side of the wall you're already on. If it's going away from you, cross over to the other side (over the top of the nose). When you reach the wall again, start sliding down the wall and fire. You can get two hits in as you slide down, then climb up a little bit and fire again to hit the nose a fourth time before it gets back to the center.
100% differences Edit
You don't need to be conservative with c.sting in this category since you don't need to fight two bosses with it, only one (and you can use a hadouken or two with decent/good rangda luck). So you can optionally use charged c.sting an extra time in the hallway between penguin and eagle refights.
Penguin always opens by spitting ice chunks at you, so dash jump over the first shot, do your quarter circle forward in the air as you land, and fire a hadouken between ice chunk shots.
Eagle always opens by flapping his wings to blow you away, so you need to get close before firing the hadouken or he'll be off screen and unhittable. Dash forward and dash jump toward eagle, then dash when you land and do the hadouken input. You can also chain together several dashes until you get close enough to fire, either is fine.
Works similarly to any%, but stay on the ground between attacks, if a blue eye or red eye opens and you aren't on the ground, it may not reach low enough for you to hadouken it.
It's technically possible to air-hadouken the nose, but to save time with it requires a 50-50 gamble on the direction the nose is going, then perfect menuing and positioning. Basically cutting everything as close as possible to failure while guessing which direction the nose will go. It's far easier to just get the one-cycle.
It's also possible to get a double kill with one hadouken on the eyes. It's not as fast as ideal eye patterns, but is better than having to kill an eye with c.sting. Only works with certain initial eye patterns though.