GetCenter.java

// "positive" is increasing positively horizontally
private float[] getHorizontalCenter(int width, int height, boolean positive) {
    float x = (width - 2 * radius) * (positive ? frame : 1 - frame) + radius;
    float y = positive ? radius : height - radius;
    return new float[] {x, y};
}

// "negative" is increasing negatively vertically
private float[] getVerticalCenter(int width, int height, boolean negative) {
    float x = negative ? width - radius : radius;
    float y = (height - 2 * radius) * (negative ? frame : 1 - frame) + radius;
    return new float[] {x, y};
}