diff --git a/src/lattice.py b/src/lattice.py
index 2f06706..06b08d8 100644
--- a/src/lattice.py
+++ b/src/lattice.py
@@ -34,5 +34,5 @@ class Square_lattice(Lattice):
 
     # draw
     def draw(self,painter):
-        painter.draw_grid(Point(0,0),self.spacing)
+        painter.draw_grid(Point(self.spacing/2,self.spacing/2),self.spacing)
         
diff --git a/src/painter.py b/src/painter.py
index 8a9fd02..45445d2 100644
--- a/src/painter.py
+++ b/src/painter.py
@@ -22,8 +22,7 @@ class Painter(Widget):
         self.particles=[]
 
         # underlying lattice
-        #self.lattice=None
-        self.lattice=Square_lattice()
+        self.lattice=None
 
         # particle under mouse
         self.undermouse=None
@@ -96,17 +95,30 @@ class Painter(Widget):
         # height offset due to status bar and command prompt
         height_offset=self.app.status_bar.height+self.app.command_prompt.height
         # vertical lines
-        # offest wrt 0
-        offset=(pos.x-0.5)%mesh
-        for i in range(math.floor((self.width/Square_element.size-offset)/mesh)+1):
+        # lines right of pos
+        xx=pos.x+mesh/2
+        while self.pos_tocoord_x(xx)<self.width:
             Color(1,1,1)
-            Line(points=((i*mesh+offset)*Square_element.size,height_offset,(i*mesh+offset)*Square_element.size,self.height+height_offset))
-        # horizontal lines
-        # offset wrt 0
-        offset=(pos.y-0.5)%1-height_offset/Square_element.size
-        for i in range(math.floor((self.height/Square_element.size-offset)/mesh)+1):
+            Line(points=(self.pos_tocoord_x(xx),height_offset,self.pos_tocoord_x(xx),self.height+height_offset))
+            xx+=mesh
+        # lines left of pos
+        xx=pos.x-mesh/2
+        while self.pos_tocoord_x(xx)>0:
             Color(1,1,1)
-            Line(points=(0,(i*mesh+offset)*Square_element.size+height_offset,self.width,(i*mesh+offset)*Square_element.size+height_offset))
+            Line(points=(self.pos_tocoord_x(xx),height_offset,self.pos_tocoord_x(xx),self.height+height_offset))
+            xx-=mesh
+        # lines above pos
+        yy=pos.y+mesh/2
+        while self.pos_tocoord_y(yy)<self.height:
+            Color(1,1,1)
+            Line(points=(0,self.pos_tocoord_y(yy),self.width,self.pos_tocoord_y(yy)))
+            yy+=mesh
+        # lines below pos
+        yy=pos.y-mesh/2
+        while self.pos_tocoord_y(yy)>0:
+            Color(1,1,1)
+            Line(points=(0,self.pos_tocoord_y(yy),self.width,self.pos_tocoord_y(yy)))
+            yy-=mesh
 
 
     # respond to keyboard