Interesting shooter! I love the art, especially the main character's design. Could use tighter controls and a little momentum in the player's movement.
The theme isn't embodied as well as it could have been. The only thing the links between bullets do is allow enemies to trigger them. Maybe limit the number of bullets the player can spawn at a time, but have the links between them remain when they are fired, damaging enemies which are passed by linked bulled on either side. This way the order you place your bullets in matters a little more.
For even more intensity you could require all the bullets to be placed before the player can set them off, forcing the player to hurry to form a chain before the enemies reach and redirect it.