Use Unity 2018.3 if you want to open the source files.
Otherwise just run the executable, instructions are included in the game.
Game programming by Jose de la Iglesia and Javier María.
Art by Lydia Ramón, Patricia Torre and Sergio Peña.
This game could not have happened without Rodrigo, Mario, Fernando, Elena, Julia, Josu and Xabier, who set the tone for what this game would be.