As a fan of Undertale, I greatly enjoyed Deltarune chapter 1. The music was great, the combat is engaging, combining more traditional RPG elements with Undertale’s combat, and the characters were very endearing. I think my favorite is probably Susie. It is worth noting though that this a very small piece of a much bigger story and you should know that going it. It along with Chapter 2 is completely free so I highly recommend it.