strokeRect(rect, color = "black", thickness = 1) {
        this.ctx.strokeStyle = color;
        this.ctx.lineWidth = thickness;
        this.ctx.strokeRect(rect.x, rect.y, rect.w, rect.h);
    }
Draws the outside of a rectangle.
@param {!Rect} rect The rectangular perimeter to stroke.
@param {!string=} color The stroke color.
@param {!number=} thickness The stroke thickness.