Code for instantiating projectiles and launching them. Set up your prefab objects for the launcher and the projectile. Code to fire the projectile and hit enemies.
Programming "agents" in your game to navigate autonomously.
Coding the enemies to ram the player, and send to the "Game Over" scene.
Program an AI agent to aim at a target and fire projectiles at it.
Deduct health from the player, and go to a "game over" scene when your health goes to zero.
Create 3D objects in TinkerCad for export into Unity.
Use the built in Unity Standard Assets to create a 2D platformer game.
Code for a player picking up some kind of "key" object, and carrying it around to unlock a "door" to advance to the next area.