请问如何实现灯泡的开关

PFont font;
void setup()
{ size(400,400);
smooth();
font=loadFont("Verdana-48.vlw");
textFont(font);
}
void draw()
{ background(100);
fill(255);
text("ON",50,310,100,100);
fill(255);
text("OFF",250,250,100,100);
fill(100);
rect(0,300,200,100);
fill(100);
rect(200,300,200,100);
fill(100);
ellipse(200,150,100,100);
if(mouseX<200&&mouseX>0&&mouseY>300&&mouseY<400)
{ if(mousePressed)
{fill(0,255,0);
ellipse(200,150,100,100);
}
}
if(mouseX>200&&mouseX<400&&mouseY>300&&mouseY<400)
{
fill(100);
ellipse(200,150,100,100);
}
}

请问如何按下一次on后使灯泡一直亮着，按下off就熄灭