So, I recently finished Night in the Woods, and I have to say, I really liked the art style. And it got me thinking, if creating game with graphics and playstyle based on another game would be considered as plagiarism? I don't mean stealing assets or copying game story, but creating something new, with similar animations, playstyle and graphics, in such way that people could notice similarities between these games.

Would such game be considered plagiarism?
Could it get me into law troubles?

This is more of general question, I don't have plans for creating such a game at this moment, I'm just curious about that stuff.

Q: Would copying game style be considered as plagiarism?

A: No.

There are concerns like trade dress, where the look and feel is incredibly distinctive.  Those can be protected if they are highly distinctive and the company is willing to spend the money on legal action.

Few games are distinctive enough it would be a concern if you are genuinely making a different game, but trade dress is one of many issues lawyers include when suing against a clone.

There are a few factors here, actually. 

1. How distinctive is the game style you're borrowing?

2. How similar are you making it?

3. Is the property owner notoriously protective of their IP?

The last one is the most practical consideration-- many companies will go after you whether a claim has legal merit or not. Anything that could be recognizably seen as "theirs" or associated with their product in some way will be suspect and possibly subject to some form of legal action, so avoid those brands (Disney and Marvel stand out). 

Similarity comes into play in 2 ways-- copyright (infringement relies on a) access, which is proven by record of this post, and b) substantial similarity-- direct copying is not the threshold, and trademark (infringement relies on likelihood of confusion in the marketplace). Depending on the country of origin there may also be some author's rights involving creative integrity that come into play. 

As a rule of thumb, any product that will immediately and recognizably call to mind in the consumer another brand or product may raise a flag and it's something we flag in clearance. 

On 12/20/2017 at 4:24 PM, XDeath said:

So, I recently finished Night in the Woods, and I have to say, I really liked the art style. And it got me thinking, if creating game with graphics and playstyle based on another game would be considered as plagiarism? I don't mean stealing assets or copying game story, but creating something new, with similar animations, playstyle and graphics, in such way that people could notice similarities between these games.

Would such game be considered plagiarism?
Could it get me into law troubles?

This is more of general question, I don't have plans for creating such a game at this moment, I'm just curious about that stuff.

Law aside (as you can get suited with or without just cause, and can end up dying from lack of funding regardless), it is generally a bad idea to outright copy one aspect of a game, regardless of what it may be. By taking an art style from another game, you've opening yourself and making yourself vulnerable unnecessarily. Pick two styles you like that don't clash too much and find a concept artist: he'll make something original out of that blend and then you can have something you like minus the danger of being suited (most likely).