In the environment, I place my previous project's pictures on the walls, And in one of the doors, I put a simple guess the word gameplay for entering.
After watching my introduction, the FPS gameplay starts, and you should protect yourself against some zombies.
I used multiple free assets for this project:
https://assetstore.unity.com/packages/2d/gui/beautiful-interface-lite-192928
https://assetstore.unity.com/packages/audio/sound-fx/creatures/free-zombie-character-sounds-141740
https://assetstore.unity.com/packages/3d/environments/sci-fi/low-poly-sci-fi-set-110775
https://assetstore.unity.com/packages/3d/props/weapons/low-poly-fps-pack-free-sample-144839
https://assetstore.unity.com/packages/tools/animation/dotween-hotween-v2-27676
https://seansleblanc.itch.io/better-minimal-webgl-template
https://assetstore.unity.com/packages/3d/characters/humanoids/zombie-30232
I did this project with Unity3d :).