As someone who hasn't really been paying much attention on this game's development, why was Forbidden Lab controversial ?
Forbidden Lab offered a lot of variety and had a few very specific kinks. It had three different routes with each route having three levels of increasing difficulty. One of them is the Huge Cock route, which gives the MC a painfully huge and heavy cock with matchingly huge balls, slowing him down massively, while also not offering much to do with a cock of that size. The little fairy women would just move away, saying the cock is clearly too huge for them to do anything with it, and the primary enemy of the first HC level was just aphrodisiac gas. In the second level, the MC would need to solve Tetris-ish puzzles while avoiding getting overwhelmed by little tentacle girls that would jump the MC, do some butt play and urethra play to get him to cum, while in the third stage, nasty robot girls would hunt the MC to insert the eggs of those tentacle girls through his urethra into his balls, which is ALMOST unavoidable and results in them hatching inside his balls, which makes him jerk his huge cock off, spitting out both cum and the tentacle girls.
The second path turned the MC into a shota-version of himself - meaning a kid - and while the MC is just a few pixels shorter (in fact, I didn't even notice it at all on my first playthrough), the implication is what threw a few people off. The stages required the MC to maneuver through a small labyrinth of rooms and hallways while trying to avoid robot nurses that bait the MC with their tits, eventually milking the MC while spoiling him. Another enemy is a pretty cool mermaid robot, which would jump out of the background and have a decent sex scene with him on the floor. The third stage has a VR-section, where the MC is in another labyrinth and has to find a way out, constantly being required to dodge some patrolling enemies as well as a time-activated enemy. (iirc) One of the endings shows that the MC can get trapped in VR, getting permanently ridden as shota while laying in a hospital bed, with a nurse telling him that the MC suffers from a terminal illness and the only way to survive is to drain his cum. In reality, the MC is strapped to a milking chair, wearing VR glasses while a masturbator is attached to his cock, ready to drain his cock to store the cum in bottles.
The third path is the probably most controversially seen path which turns the MC into a furry version of himself, where he needs to avoid getting double-teamed by rabbit girls, getting sucked off by sneaky mouse girls, gets hunted by a giant, multi-titted rat woman and during the third level, the MC needs to get through another maze that can possibly send him into a cellar trap, where a giant frog woman unbirths him if he fails to escape the smaller frog/tadpole girls.
Finally, the actual boss of Forbidden Laboratory is a slug-like robot amalgam woman that has plenty of different sex scenes ready for the MC. Among them are a titjob, a blowjob, four rather similar multi-tit-fucks and another unbirth scene, where the MC right before getting stuffed into the slug vagina gets drilled by a drilldo in the butt.
Generally, I myself didn't like some parts of it, but honestly, it's just fair since there are a lot of fetishes out there, and there are probably a lot of people who appreciate the furry part, the unbirthing scenes (altogether with the one from the Level 1 boss) and the urethra stuff/butt play. I think Castle of Temptation could have used a few more blowjob scenes, sex scenes utilizing the huge cock part of Forbidden Laboratory (like the factory ending, chef's kiss!) and I found there could have been done a lot more with the bondage section in Mother's Chapel (hence the fan-arts I made earlier with the MC becoming a leather-clad incubus chained to the walls, serving as cum dispenser, or the one of a demon girl blowing him), but I think the game offers really a lot, especially if you keep the secret sections of each level in mind. And I think the more abstract fetishes in Forbidden Laboratory and, actually similarly, in Mother's Chapel, too, are quite well integrated into the game as optional pathways, so people are not forced to play through certain H-scenes at all.