customDraw() {
        var ctx = simulationArea.context;
        const xx = this.x;
        const yy = this.y;

        ctx.beginPath();
        ctx.fillStyle = 'Black';
        ctx.textAlign = 'center';

        fillText4(ctx, 'I', -10, 0, xx, yy, this.direction, 10);
        fillText4(ctx, 'O', 10, 0, xx, yy, this.direction, 10);
        ctx.fill();
    }
@memberof ForceGate
function to draw element