Physics engine: One of the most important parts of a rollercoaster mod is the physics engine. You'll need to create a system that simulates the movement of rollercoaster carts along the tracks, taking into account things like gravity, centripetal force, and friction.
Track generation: Once you have a working physics engine, you'll need to create a system for generating rollercoaster tracks. This could involve placing blocks to define the path of the track, or using a more advanced system like splines to create smooth curves and loops.
Cart behavior: You'll need to create a custom cart entity that can interact with the physics engine and respond to player input. This could involve implementing features like brakes, acceleration, and the ability to tilt the cart for tight turns.
Special effects: To make your rollercoaster mod really stand out, you could add special effects like particle effects, sound effects, and camera effects. For example, you could create a system that generates sparks when the cart grinds against the track, or adds a blur effect when the cart goes through a loop.
User interface: Finally, you'll need to create a user interface for players to interact with your rollercoaster mod. This could involve creating custom GUI screens for building and editing tracks, or adding a custom HUD that displays information about the rollercoaster's speed, acceleration, and other metrics.