Is there a way to build a custom app for lichess?

I want to make a chess game is it possible to integrate it with lichess so people can play on lichess thru my app?

Are you saying you have designed what you would call a superior interface to Lichess?

I have studied lichess code, and I want to build a chess game with a simplistic pixel art graphics, in any case I wonder if this is even possible.

Yes, but third party apps allowed to play through BOT API only!
See https://lichess.org/api