This battle is very hard, just a warning. Not as hard as my past battles, but it's still very hard. I've beaten it once, but it took about 30 tries to get the hang of it. Also, not attacking Napstablook is the way to go. Attacking him is possible too, but's much harder. One quick note: Can be finished at minimum in 7 turns.Good luck!
All credit to pcocikapusta for his amazing tutorial on making undertale battles. Check him out! :) Also, credit to Toby Fox for making us this amazing game in the first place! You should check out the real game too, because it's fun and has an awesome story-line. Also keep in mind, having music on when the flowey nuke attack is happening can be quite loud. Just a disclaimer. And finally, credit to Napstablook for being my favorite character :)