1) Create five levels in which the player needs to explore in a controlled way. The level should have a start point and an end point. Think about how far / high characters can jump to keep parts blocked off.
Make sure you control how the players can progress through the level with terrain. You should use Probuilder, MagicaVoxel, or both to design your level. You can also use other resources such as physics materials.
2) Add at least one "hidden area" to your level.
3) Add at least one area which requires an item to progress.
4) Create one power up for your character (different than the progression item).
5) Use slime enemies in the environment. If your player touches a slime, restart the level (or if you are feeling like a bit of a challenge, make checkpoints and move the player to the last touched checkpoint).
6) Create at least one additional "humanoid" enemy complete with animations. Make sure the player can interact with the enemies in some way (attack, avoid, etc)