Visual novels in general are probably the most "safe" genre of video games as far as the player being able to dictate their own experience.  Interaction is limited to advancing dialogue and choosing branching paths.  You can save your game at any time and reload if you want to change a choice you made.  At no point in any visual novel are you not in 100% complete control of the game and how you experience it.  DDLC takes that expectation, and spends the first couple of hours building that sense of control in the player before slowly pulling it farther and farther away. 

Selecting certain options starts to cause the game to glitch out ever so slightly before jumping onto a different dialogue path than the one you chose.  Assets don't always load in quite right;  CGs are just a little bit off from the first time you saw them.  As the game progresses, the protagonist you're playing as slowly winds up getting less and less dialogue even as the girls continue to talk to 'him.'  The choices you actually do get to make become fewer and far between, and moments where you have any actual influence or control become all but non-existent.  The longer you stay in the game, the less you feel like you're in control of what's happening.  It's great.

There's even an extra layer of creepiness and horror built in for those who try to be clever and root around in the game's data to find stuff.  If you want the full experience, open up the game's files, take a second to familiarize yourself with what's in there, and then leave that window open and in view while you play.

The game is very short. It took me 2.3 hours to complete the game.

Despite its length, it manages to tell a nice story in its time. The mysteries that the story presents drive you to want to find out more. The main characters, Resette and Gaede, are very cute and charming. They are portrayed as if they are part of a larger overarching story, with this game being another chapter of their adventures. However, outside of the manga in the artbook, I'm not aware of them being involved in any other stories. A tad disappointing because playing this game makes me want to know more about them and their experiences.

As a point and click game, there are a lot of puzzles. A good portion of these puzzles are decently easy to solve once you figure out how they work. (Except for that one early puzzle I brute forced.) Though, they are not too easy as I wasn't bored with solving them. The only difficulty I had was noticing special objects or paths because I'm apparently blind. :/
This game has no hint system at all. So if you get stuck, you will need to search online for a let's play, because guides for this game apparently do not exist.

The game introduces you to a basic tutorial at the beginning. When your cursor turns into a pair of boots, clicking will have Resette or Gaede walk there. Movement kind of gets funky at times as sometimes you're not quite sure how far you're allowed to walk in a particular room. An area that looks walkable actually isn't since your mouse doesn't turn into boots. Meanwhile walkable areas appear to be unwalkable if your mouse just so happens to be out of the hit box for the walkable area. Despite how awful this may sound, it's actually not too much of a problem. But it's can be noticeable at times. If there's something you can interact with, your mouse turns into a feather. However since your character needs to be close to that object for the feather to appear, sometimes you may not realize that an object is interactable. Combine that with the occasionally awkward movement, this makes finding interactable items and objects a little harder than they should be.

Another complaint I have is that I really wish Resette could interact more with Gaede. Having them talking to each other in different rooms and/or at different times could have helped develop them or revealed more of their relationship with each other. Their conversations could have been them commenting on the situation or the room they were in. Gaede could maybe even give hints to puzzles or items that should be examined. What happens instead is that Gaede usually just follows Resette, only commenting when interacting with certain objects; or he just stands there and does absolutely nothing until you move onto the next room. This really feels like missed potential.

In terms of audio; there's nothing special for its minimal sound effects. What they have works. Note that the game does not have any kind of voice acting whatsoever. As for the music, this game has a lovely soundtrack. It is very nice to listen to and is probably one of the strongest points of the game. I wish I had the words to describe exactly how much I like the music.

The art is quite nice. The backgrounds are full water colored paintings while the characters are drawn clearly. The two art styles may seem funky at first, but it grew on me. The animations for the characters are pretty weak however. Many of them are choppy, as in they only have a few frames for their animations. This works fine for simpler movements such as walking and running, but it becomes noticeable during the parts of the game where the characters are doing something more important.

tl;dr: Short, nice story, charming characters, funky hitboxes for interaction, easy difficulty, pretty art, choppy animations, excelent music