Diamond is not Crash
I designed DINC Mine as an assignment for my Level Design II class, encompassing everything I had learned up until that point. The entire level takes place in an abandoned mine, where the player's only motivation is to reach the top, symbolized by the glowing moonlight from the surface. Though the player has no idea how they got there, they for some reason have the ability to stretch out certain surfaces on the wall to use as platforms. Using this ability, the player will try to make it to the top without falling to their death from the many dangerous obstacles that present themselves.
By making the level progression involve going back through the center at increasingly higher points, the player gets to reflect on their progress, giving a good incentive to keep moving forward. Along with this, randomly generated sounds with differing volumes such as rocks falling and shifting machine parts give the player a lingering sense of dread as they keep moving up the level.
Give the player the sense of always progressing upwards through the mine.
Create a sense of dread and loneliness through the level/sound design to always keep the player on edge.
Give the player the ability to speedrun sections only if they have the necessary skill required.