An updated review on my last to make it more comprehensible and detailed, the reason im leaving the old one up is because i don't know how to delete it lol.
The good:
Despite how simple it is, the moveset is quite fun to use. Especially the mid-air speed charge which lets you fling around the level and be just as mobile as other addon characters with proper use.
The act clear theme being changed to a snippit of Prey is cool!
The bad:
The custom sprites for Furnace are... odd, especially the behind movement sprite which janks around weirdly.
The CSS info does not stack up to the quality of other characters, missing proper grammar and cosmetic word coloring.
Suggestions:
Turn Furnace fully 2D (until sprites are complete) with some kind of script to prevent any sprite problems, as alot of the sprites used are poorly applied and made (no offense).
The mid-air speed charge move has no cap on how long you can charge it, it should probably get a cap of at most 120.
The moveset is a touch lackluster, maybe swap out a few moves/modify what Furnace already has?
When Furnace is named in it's own CSS info, Furnace's name should have a grey color instead of the default white (The same should happen w/ Starved, but with Crimson/Red)
The creators/owners of Starved and Furnace should be credited on the addon page, i am unable to link them here though as the MB restricts it.