Interactive Grid

def setup():
    size(800,800)
    noStroke()
    background(0)
    
    global grid, max_dist, d, distcolor, w
    grid=[[2]*8 for n in range(8)]
    print (grid)
    max_dist = dist(0, 0, width, height)
    w=40
def draw():
    # for i in range(0, width):
    #     i+=20
    #     for j in range(0, height):
    #         j+=20
    #         distcolor=dist(mouseX, mouseY, i, j)
    #         d=distcolor/max_dist * 35
    #         strokeWeight(1)
    #         stroke(200)
    #         if (distcolor>max_dist):
    #             fill(255)
    #         else:
    #             fill(distcolor*255/2000)
              
    #         ellipse(i, j, d, d)
    x=0
    y=0
    stroke(0)
    sp = 10
    for row in range(width/w):
        for col in range(height/w):
            if int(mouseX/w)%2==0 and mouseX>=(x+col*w) and mouseX<=(x+(col+1)*w) and int(mouseY/w)%2==0 and mouseY>=(y+row*w) and mouseY<=(y+(row+1)*w):
                fill(255,0,0)
            else:
                fill(250)
            rect(x+col * (w), y+row * (w), w, w)
            x=x+w
        y=y+w
        x=0

The white square will turn red if you put the mouse onto it.