I have some suggestions and grammar improvements.
This should'nt be happening -
This shouldn't be happening
The dog is playing the marucus -
The dog is playing the maracas
Now that your here -
Now that you're here
ok now for the suggestions
For the music deltarune gaster has a different theme called another him
you don't have to use this but heres a remix i think it fits him well
also i don't know anything about coding and i don't know if you can put gifs into it but this would be cool as like a background during the fight idk
so yeah!!
i really liked your fight btw. i think gaster in deltarune deserves more attention