Morgan McGuire, 2017. Open Source under the BSD or MIT license--your choice!

This is code demonstrating how to simulate player-character movement in a 2D platformer with the following features:

• variable ground friction (e.g., ice)
• gravity
• terminal velocity
• jumping
• variable-height jumping
• hazards (e.g., spikes)
• wall-sliding (w/ variable friction)
• wall-jumping
• early jump grace period (http://kpulv.com/106/Jump_Input_Buffering/)
• late jump grace period (http://kpulv.com/123/Platforming_Ledge_Forgiveness/)

This is programmed in the style of PICO-8 lua with the assumption of 8x8 pixel sprites (which is why it has only lower-case letters and is designed to minimize tokens). See:

• platformer.lua for the fully-commented version and
• platformer-min.lua for a more minimalist version.

This assumes the following functions:

• hsolid(x, y1, y2) returns true if pixel (x, y1) or (x, y2) is solid with respect to horizontal movement
• vsolid(x1, y, x2) returns true if pixel (x1, y) or (x2, y) is solid with respect to vertical movement
• friction(x, y) returns the friction multiplier (tuned for 0-8) for the block at pixel (x, y)