Since you want to make longer game, why not start the game with normal setting? normal means there's nothing strange nor scary, just normal atmosphere and player's stats are normal. The game mostly could be anything such as RPG or point n click. Platformer and shmup could also work.
Then after halfway through the game, change the normality drastically, player moves slower and/or attacks weaker than normal. Atmosphere is changed to scary. Tension is increased.