Rivium is a top-down action-adventure game made in Unity where the player must gather buried treasure. I made it by myself over the course of a semester. It was chosen by my professor to be shown at the Game Center's 2017 Student Showcase, one of five freshman games on display out of 60 games.
I built the game around one complex central mechanic. When the player's bag is empty, they are quick and evasive, while lacking any combative potential--when they fill their bag, they gain massive offensive capabilities while becoming slow and heavy.
Because Rivium's core idea is very complex, the biggest design challenge I faced was presenting the mechanic in an intuitive way that would not alienate new players. The first decision I made was to move away from the long-form adventure game format I had originally conceived and instead design the game around a snappier, Super Meat Boy-inspired gameplay loop.
I separated the level into five rooms, each with a checkpoint and an objective. Each room would require multiple tries, but would instantly respawn the player at the beginning of that room to prevent the game from getting frustrating. Despite a player's lack of skill, they could try again immediately, and every attempt would develop their knowledge of the game.
The main feature I decided to retain from the original design was nonlinearity, which separates it from fast-paced action games like Meat Boy. The "levels" in the game are only implied, and the order they can be encountered in can change. Giving players agency over the path they took through the environment was the key to retaining the atmosphere an adventure game while keeping focus on the mechanics.