make the sprites separate from the background(I need both an overworld and a battle sprite( I will make notes of every character picked in the studio when the character is picked they will be added there fill it out when you remix don't forget that there are still normal enemies if you want to have multiple of your character also you can make Omega sprites for your character if they replace Flowey if you want I will need them I will choose HP ATTACK DEFENCE EXP gained and G gained accordingly Asriel is an option even if Flowey was already chosen(if Asriel is picked might be rejected even if nobody picked it yet if I don't feel like its a good idea so if you pick Asriel make sure you have a back up plan)
The battle sprites aren't black and white, but you can fix that all.
