Looks decent enough, especially for a one-man project.

Is that Sir Whoopass at 0:04 in the trailer lol?

Well Sir Whoopass was an asset flip done right, so I'll give Ghoul Castle 3D a chance too. It's cheap at least.

Instabuy

The graphics look alright and good enough for me but the combat animation is very simplistic but acceptable for that incredibly low price. Almost makes me wonder how simple the game is if it is that cheap. Nethack et al come to mind when I saw the trailer.

How long is this game? And is it good? :D

According to Howlongtobeat.com, it'll take just over 4 hours to beat/finish...

https://howlongtobeat.com/game/101579

Some of those bullet points... o.O Whatever head-to-head combat is supposed to mean. =P That gameplay trailer certainly didn't make it look very intense.

Must complain: was hoping for a party-based one ...

Just watch this:
https://www.youtube.com/watch?v=m4qKziSejrE

He says it's rather on the easy side so I think I'll get it. The price is a steal anyway :)

Anyone else having a problem falling through the floor?

No, didnt happen to me. In what level does this happen?

The developer (or whomever from the publisher wrote that copy) presumably doesn't really understand what "head-to-head" means (since there's no indication that the game has multiplayer). :D
Meanwhile, I was scratching my head more at the page's claim of "gameplay just like famous retro shooters". I mean, yeah, it's real-time with free (i.e., not grid-based) movement. But even leaving aside the fact that it's apparently mostly-to-entirely melee-based, the gameplay seems to be a hell of a lot slower than in the vast majority of those shooters (apart from maybe the really early ones, like Wolfenstein 3D). That's like saying a hypothetical new Diablo II-style ARPG has gameplay "just like classic RTS games" just because they both involve point-and-click controls and the viewing perspectives are similar. Why make confusing comparisons to games from a rather different gameplay genre?

Yes, there is a glitch at the end of the Level "Hallway of Pillars".

After the second run i will report if it is possible to finish the level.

Edit:

Ok, it is possible to complete the level. Before you reach the boss fight, ignore the two guards and go straight up the stairs to the boss. That works.

Level 6