What a masterpiece of a game. Wow.
Art, original music, and writing are all superb. Graphics could have been more detailed, but the art style makes the graphical detail (resolution) not as important, and even more fitting in a way for the darker and granier feel to the game. Voice acting is some of the best I've heard in a game making all the characters believable and worthy of your investment in them. Especially the main female protagonist, who is very unique for the gaming world and isn't constrained by the typical gaming tropes.
The writing and character dialogue is by far the most mature and believable for any game I have played. You are getting adult level dialogue and script writing here with very few, if any instances of the kind of cheesy video game writing we have grown to expect from video game writers.
This story will present some very dark themes. Depression, suicide, murder, and any other dark thoughts you could have. It's not technically a horror game, but it is psychologically creepy enough to feel like it at times. Something that most of us who no longer feel any fear from the "horror" genre are more likely to find unnerving in parts due to it being much more about the emotional level of the characters and their mental state rather than just seeing a ton of gore. This game does have several strange and gorey scenes in it, but that isn't really what makes it great. The depth of the characters' thoughts and emotional upheaval is what makes it shine in the end.
The atmosphere of the game as well as all the set designs capture the mood of the story and the characters perfectly. The grainy sadness of the entire game keeps you in a perfect mood to enjoy the tale you are presented with.
For anyone that has experienced sadness, or depression on a deep level, this game will be relateable to you in many ways I'm sure. Living with the inability to properly address negative emotions that keep you in a state of sadness is perfectly presented here. Living with depression has never been shown better in a video game that I have played. You feel like you really know the main character, and you feel like the writer has a deep understanding of why she is the way she is.
There are well designed puzzles along the way that adventure fans expect. It is definitely possible to get a bit stuck and not be able to figure out a puzzle as some are a bit unorthodox, but if you look hard enough and think about all the interactible items in every stage eventually you can figure it out. Nothing too difficult, however.
This game deserves far more recognition than it gets. It is a truly great work of art, and it is quite apparent that the developer put a lot of deep thought into making this game. It absolutely had to have come from personal experience with the things presented. I don't think you could make a game like this unless you understand, or have studied many of these themes in depth.
EDIT: All this below is for completionists/replays and Achievement hunters. NO SPOILERS are here other than very minor ones about early game decisions in the first few minutes.
I completed all the Achievements in this game now so I can give a bit more description on how much choices you can make change the game.
If you want to make sure you get the "Best" ending you have to pay really close attention to what you do from the very first choice in th egame as any mistake will give you one of the normal endings instead. You should look at the achievements guide to be sure and follow the 'A Flower That Bends Towards the Sun' description to get you this ending.
HERE is the Guide to use: http://steamcommunity.com/sharedfiles/filedetails/?id=201219437
WARNING: the engine this game uses doesn't allow you to overwrite saves, and the save limit is 50. That may seem like a lot, but I DID hit it, so you may need to cut some of your saves and put them into another folder for later if you need more room. The save folder for this game is located in:
C:\Users\<yourPCName>\Saved Games\Cat Lady
As far as I can tell there are 5 endings, but there are many choices along the way that can change dialogue for the section that it is in. Ch. 2 for example has several different pieces of artwork based on the answers you give to questions asked of you. This section probably has the most alternative story element in it so saving here is worth doing to allow you a pk at as many as you can see. These aren't things that will impact the ending necessarily, but worthwhile for small little flashback scenes that are quite good. Achievement, or not. Th eCh. 1 decsion I wonder about for the ending as one side (perfect ending) does require it, but not sure if the other does.
EDIT #2: I have played with the Ch. 1 decision taking the side that doesn't get the perfect ending all the way through to the en, and I can confirm that taking this choice does not change teh ending other than making it impossible to get theerfect nding. All the normal endings will basically the same if you take the choice that gives you the other Achievement for Ch. 1.