Level Design
A lot of thought went into implementing the Five Stages of Grief.
The Anger section of the game takes place in tighter areas with more difficult and precise obstacles than what has previously been presented to the player.
Combined with the red color scheme and relatively large amount of spikes this would give the player subtle feelings of anger and frustration when trying to continue the journey through the game. Balancing this was a big focus since a section which was too hard would destroy the fun in the game and ultimately leave the player frustrated and unwilling to continue playing the game.