[pygame] A little help please

[Silver]

I need some help with a program that I'm trying to write with pygame.

I am having two issues:
        * the squares aren't being drawn 1 px small so that they leave a black 
grid
        * the squares on the edges are extending, even though I don't think I
told them to.

anyone know how to fix it?

import pygame
import math


squaresize = 64
sqsz = squaresize

width = 799
height = width

radius = .5*sqsz

pygame.init()

screen = pygame.display.set_mode((width,height))

while True:
    pygame.event.get()
    mousex = pygame.mouse.get_pos()[0]
    mousey = pygame.mouse.get_pos()[1]
    screen.fill((0,0,0))
    for x in xrange(width/squaresize):
        for y in xrange(height/squaresize):
            hx = x
            hy = y
            hx *= sqsz
            hy *= sqsz
            #print hx,hy,sqsz, sqsz
            nx = hx+(sqsz/2)-mousex
            ny = hy+(sqsz/2)-mousey
            nz = ((nx**2)+(ny**2))**.5
            if nz == 0:
                nz = .0000001            #print nz
            n = radius / nz
            if n == 0:
                n = .0000001
            if n > 1:
                n = 1
            
            #print n
            color = n*255
            #print (color,color,color)
            #print hx, hy, hx+15, hy+15
            pygame.draw.rect(screen, (color,color,color), 
(hx,hy,hx+sqsz-1,hy+sqsz-1))
    pygame.display.update()