week17 物理學

void setup(){
   size(300,300);
}
float x = 200 , y = 150;
float vx = 0 , vy = 0;
void draw(){
   background(#002966);
   stroke(#b7efff);
   line(100,150 , x,y);
 
   fill(#b7efff);
   noStroke();  //圖案變成無外框
   ellipse(100,150 , 13,13);
   ellipse(x,y , 13,13);
   // <物理力學>
   if(!mousePressed){  //滑鼠沒按       
     float dx = x-100, dy = y-150;
     float len = sqrt(dx*dx + dy*dy);
     // <虎克定律(Hooke's law)>
     vx -= dx*(len-100)/len*0.01;  // *彈性係數
     vy -= dy*(len-100)/len*0.01;  // 越大彈簧越快
     x += vx;
     y += vy;
     // </虎克定律(Hooke's law)>
   }
   // </物理力學>
}
void mouseDragged(){  //滑鼠拖曳
   x = mouseX;
   y = mouseY;
   vx = 0;
   vy = 0;
}