@kayahr Thanks for the reply! Surely most engine nowadays come with nice features inside it, official packages to download, and a community to gather other resources to work on. Some things came from outside sources, as you pointed out. Like the 3D model assets that came from the Kenneys Assets (https://itch.io/s/29028/kenney-10-year-anniversary).
Unity has a built-in pathfinding system to use, the outline effect was adapted from a open source project from the community, the Cinemachine package was used to make camera dynamics in the beginning cutscene, and the dialog system used is adapted from a open source project I am currently working on.
These are tools we used to construct the game as you see it.
But, surely, there are several other code, assets and game design that was created from scratch in this 72 hours. The enemy rudimentary IA (routes and behaviour), movement controller, plot, the level design, concept, sound design, sound sampling, sound controllers (whisperers and heartbeats), main menu music composition, User Interface icon design.
Soon we will open the project source code to anyone that was curious in how we made this game. We will, as well, write a richer itch.io page to describe what we done and the tools used. Feel free to see it and ask about anything :)