/* built with Studio Sketchpad: 
 *   https://sketchpad.cc
 * 
 * observe the evolution of this sketch: 
 *   https://playgramming.sketchpad.cc/sp/pad/view/ro.8q6NdfG63JW/rev.71
 * 
 * authors: 
 *   Devon Scott-Tunkin

 * license (unless otherwise specified): 
 *   creative commons attribution-share alike 3.0 license.
 *   https://creativecommons.org/licenses/by-sa/3.0/ 
 */ 



float beginX = 20.0; // Initial x-coordinate
float beginY = 10.0; // Initial y-coordinate
float endX = 70.0; // Final x-coordinate
float endY = 80.0; // Final y-coordinate
float distX; // X-axis distance to move
float distY; // Y-axis distance to move
float exponent = 3.0; // Determines the curve
float x = 0.0; // Current x-coordinate
float y = 0.0; // Current y-coordinate
float step = 0.01; // Size of each step along the path
float pct = 0.0; // Percentage traveled (0.0 to 1.0)
int direction = 1;

void setup() {
    size(100, 100);
    noStroke();
    smooth();
    distX = endX - beginX;
    distY = endY - beginY;
}

void draw() {
    fill(0, 2);
    rect(0, 0, width, height);
    pct += step * direction;
    if ((pct > 1.0) || (pct < 0.0)) {
        direction = direction * -1;
    }
    if (direction == 1) {
        x = beginX + (pct * distX);
        float e = pow(pct, exponent);
        y = beginY + (e * distY);
    } 
    else {
        x = beginX + (pct * distX);
        float e = pow(1.0-pct, exponent*2);
        y = beginY + (e * -distY) + distY;
    }
    fill(255);
    ellipse(x, y, 20, 20);
}