Eternal Euthymia is a dating simulator, a mash-up of Doki Doki Literature Club by Team Salvato and Genshin Impact by HoYoVerse/COGNOSPHERE. There is no game engine - the game is playable using Google Slides, inspired on the parody game High School Impact Monoceros Caeli by @rulainyu on TikTok.
You play as a transfer student in a high school called Inazuma High. Throughout the game, you meet various characters and befriend them. Any one of them could confess their feelings to you at any point of time over the course of six acts, excluding a prologue. You make decisions and choose endings. The duration of your gameplay varies based on what choices you make.
All assets used in game were either created by the developer of the game using Google Slides tools, or official art and assets owned by COGNOSPHERE. Sprites are made by the developer. All due credit is given at the end of a game in a dedicated slide.