In the arcades, games were difficult on purpose to make the player put more coins in, in the first consoles, games had artificial difficulty to make up for the lack of content that the games had.
Easter eggs are a great way to make the player feel good/amazed if they discover them, or even if they watch someone else discover them.
Here are some other experiments with shaders in Unity.
A shader is a program that indicates how an object should be shaded in the rendering process, it indicates what color a something should have at a certain position.
In Dig-Dug you take the role of a guy with an air pump that needs to inflate underground animals until they explode and die.
Galaga is a shoot ’em up where you need to destroy the alien ships while avoiding getting hitted by the ships or by their projectiles.
Here’s a mini-analysis on the mechanics and AI from the original Pac-Man.
I’ve tried to optimize the number of verbs from Maniac Mansion.
Tangential Learning is an interesting subject to treat in the realm of game design, here’s an example on how it’s applied in an old retro game.
Having a grasp of the different kinds of ways to learn will be useful to learn how to arrange the different systems in your game to incentivise or demotivate certain behaviors from your players.