Love the idea, the execution is pretty fun, and the presentation is great! Though its flow is a bit broken up.
The idea of laying out your shots in greater and greater number and then unleashing a salvo before the enemies send it back at you is a fantastic idea, but, with all the shots moving in one direction and enemies coming from all directions I feel it sort of de-incentivizes the player from actually building up long chains, perhaps instead shots could fire off in the direction of the closest enemy or launch out away from the player, the first would probably feel better from a power perspective, but, could be a bit much depending on what you're going for with the feel of the game, the second would have more strategy to it, but, also require more from the player to really get a lot out of it.
Though if firing in a singular direction is the real aim and feel, perhaps instead the projectiles could fire in the opposite direction to your dash, sort of launching them back away from you, as currently if enemies get too close there is not really a way to deal with them, this may also make the projectiles feel like they are being launched with more force due to the player sort of being "knocked back".
All in all, I think the concept is spectacular and it'd be really cool to see where you'd take it if you plan on continuing to develop it. Great entry and fantastic work!