What would you make of this?

You are playing an FPS.

The character moves fast.

REALLY FAST!

You have a set of moves that allow you to go insane speeds through large swarms of enemies.

Suddenly while doing one of these moves there is an explosion with you in the center and all the enemies get knocked back.

The explosion is a burst of air with no fire.

What would you think it is?

 

Sonic Storm. (Sonic Boom)

 

Okay, I was wondering if anyone would be able to make sense of it. I cannot think of a single video game that has ever had a sonic boom.

well, other than Street Fighter 2.

maybe the achievement should be “guile would be proud”. Lol

 

I tend to image a fantasy wizard-combat shooter. Many mages in many games have this powerful spell with which they push-back close-by enemies in 360° degrees since a fragile character like a Wizard can't afford to be engulfed by enemies.

 

The first thing I thought of was comic book style speedsters. They go really fast and can use that speed to cause all kinds of special effects like tornadoes, sonic booms, whirlpools, and lightning.

 

Yeah, it’s really not that kind of game.

It’s an FPS Metroidvania, but I’m playtesting I’m finding that under the right circumstances the player can reach incredible speeds, so I’m thinking I want to add a sonic boom if they manage to go faster than sound.

 

It would need good feedback to convey what's happening to the player -- like a sonic boom sound plus a distortion shader.

 

Well, it would be such a rare occurrence that probably only top tier speed runners would get any use out of it.

 

Then they definitely deserve a nice little audiovisual reward.

 

What causes this explosion? Is this some random thing that happens unintentionally, when using a special move, or does the explosion occur everytime you use certain special moves?

 

It’s a sonic boom.

I want there to be a sonic boom if you go faster than sound as an Easter egg, and really only be possible under the right circumstances.

 

I think the audio would be the most important part of telling the story here. Also a shockwave ripple distortion effect would be cool.

 

A glitch.

A sonic boom seems like an instantaneous effect to a stationery observer, but that's just the moment that the wavefront reaches their position. The shock wave is continuous and would follow the object causing it.

I am fully aware that realism != effective game design, so take that with a grain of salt, and feel free to completely ignore it. Games do nonsensical stuff for the sake of fun all the time. That said, if it was going to be explained as a sonic boom then, to my overthinking and critical mind:
1. Once it starts it should continue as long as momentum is maintained.
2. I'd expect to see hints of the building wave-front before I caught up to it and it became fully compressed.