Parse

File Parse gravity.js

Source

            /*

The _gravity_ reactor adds 2D motion in a direction 
Apply many points to the reactor, and step every frame:

    gr = new GravityReactor(gravityPoint, points)
    gr.step()

Note: this isn't a _mass_ reactor (where points tend towards each other)
*/

class GravityReactor {
    /* The reactor updates a point list, pulling all items in a direction
    provide a point as the directions for gravity. 0,0 for no gravity.*/
    constructor(gravityPoint, points, lockedPoints=[]) {
        this.gravity = gravityPoint
        this.points = points
        this.lockedPoints = new Set(lockedPoints)
    }

    step(delta=1, lockedPoints=this.lockedPoints) {
        // Apply gravity
        const gravity = this.gravity
        const lp = lockedPoints
        this.points.forEach(p=>{
            if(lp.has(p)) { return }
            p.x += (gravity.x * delta);
            p.y += (gravity.y * delta);
        })
    }
}
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