Disclaimer I dislike futa. This game is heavily futa-focussed. Despite this, I still love this game. This review examines why.
Graphics 7/10 - RPG Maker standard assets, not really anything noticeable custom. It's tastefully enough arranged, but it's still standard.
This being said, the renders for the actual scenes (seventeen scenes in total at the time of writing, many are variable in some way) very much are custom and well-made. No anonymous standard asset dicks here.
Sound 6/10 - People play their porn games with sound on? Okay... but yeah, again, nothing extraordinary here. Actually, the bunnies' guild theme gets on my nerves, but...
Gameplay 9/10 - this may be missleading, and also depends on what one understands to be 'Gameplay' in a porn game. Although there are seventeen scenes in total, the game is long, and the time between scenes can be considerable. Others have criticised this as a negative, and while I don't care myself, this criticism isn't without merit.
However, Proxxie clearly has aspirations for making this a game, not just porn in a game format, and thus has added legit gameplay. Fights require you to think and are oftentimes unconventional, not simply asking you choose menu options, but to think creatively and solve simple puzzles. This can occasionally be difficult enough that you'll sit on a given puzzle for a while, or you'll lose a fight a couple of times, but it's never unfair, just moderately challenging. Ordinarily, I'd consider this a cardinal sin for a porn game, but here it actually works for me and provides some sense of accomplishment, something rarely seen in these types of game.
Proxxie also seems to hate grinding, and thus eliminated it from the game altogether - don't be chasing xp, 'cause you ain't getting any from slaughtering smaller enemies. Only after a major challenge will you be provided with a level-up (loosely akin to Zelda, if in a stat format). Coincidentally, this also means that there's no cheesing those fights through grinding, and trying to avoid minor opponents actually makes sense for once. All gameplay choices I approve of.
Minigames are aplenty (not always required) and variable enough to be fun without becoming repetitive.
Other cardinal sins - i.e. lose/gameover to get a scene - are nowhere to be found here, and good riddance to that rubbish.
Ultimately docking a point since the criticism concerning times between scenes can be considered valid (though I personally believe that blanketing the game with scenes would ruin it, more on that later), but this doesn't change the fact that gameplaywise, this is arguably the best erotic game I know of.
Story 9/10 - Story in porn? What's next, reading porn mags for the articles?
Well. Here's the thing. As mentioned earlier, Proxxie clearly aspires for The Proteus Effect to be more than just a 'Porn Game', is aiming for legit RPG chops. RPGs do in turn thrieve on story and characters, and the characters are The Proteus Effect's shining jewel.
It's not perfect - Proxxie is self-admittedly not all that great at writing male characters - but the protagonist's and her party members' characterisation and character development, the sense of humour permeating every corner of the game time and time making you laugh out loud, and making you laugh with the game, with the characters, not at them.
The protagonist is incredibly cute and adorably... not especially bright, but well-meaning, her partner Ana is an incredibly well-realised feminist, not a caricature but having a point, yet still fitting just fine into this game, with her character undertaking a journey from accidentally being trapped with the protagonist to becoming the protagonist's friend to (eventually?) becoming something more. There's the Very Evil Warlock who really likes cute dresses and totally despises humans and only helps them out of necessity, no other reason. Even NPCs occasionally get clever, become characters in their own right.
The overall plot sounds trite - 'Trapped in a videogame? Was the shitty Isekai LN thing already going on when 0.1 was released?' - but it's but a backdrop for character development.
And that character development does, of course, first and foremost focus on the (virtual) MtF transformation of the main character. There's a reason the game is on TFGS, after all.
Overall 9/10 - And maybe that last paragraph is a bit of a hangup for F95. As said earlier, Proxxie is aiming for a game, not just porn in a game costume. Actual porn scenes are - relative to the length of the game - rare, but the focus of the game is less porn and more the protagonist dealing with hir change - and dealing with it positively. No wailing about how being turned into a woman is the worst thing ever (tell that to the other half of the world's population...), but coping, adapting, even enjoying.
And this is something that can be done without porn scenes. It can be done - and to a considerable extent, is being done here - through gameplay, through the natural flow of the story in a legitimate RPG's text boxes.
Ultimately, at the end of the day, I'd say that The Proteus Effect is a transformation game that happens to also contain porn (even if this wasn't necessarily the creator's initial intention, given that Proxxie considered spicier material he eventually shied away from). For that reason, it's entirely possible that people who are just looking for a quick fix are turned off by it - and there's nothing wrong with that. Tastes, desires vary.
But for anyone who is looking for a little bit of actual gameplay, for anyone who is looking for entertainment, for comedy, for brilliant dialogue and wit, and is willing to wait for a bit before having a wank, this game is a gem that shouldn't be missed out on.
Even if you're like me, dislike futa, and play the game with your pants on.