Baking a cake is a labour of love but also just basic chemistry, you're mixing ingredients together and making it react into something typically delicious. But each ingredient is important! Leaving out eggs or baking powder or butter can change the cake dramatically. Here's what a cake looks like without one of those ingredients.
The baking was done by At-Bristol in the video below. They explain the role that each ingredient performs and why each ingredient is important (for bonding, for rising, etc.). The cake that's missing the egg is such a sad, sad thing.