Sure! Here's an example of how you can implement the game of a square walking in a box and getting creepier every 5 seconds. The background will darken gradually, the movement speed of the square will decrease, and the visuals will become more corrupted:
In this game, the square starts moving from the left side of the box towards the right side. The background gradually darkens by 5% every 5 seconds, and the movement speed of the square decreases over time. The `filter` property in the CSS animation adds a creepy effect by reducing the brightness of the square at certain keyframe intervals.