diff --git a/help.lua b/help.lua
index f979b2f..7b56835 100644
--- a/help.lua
+++ b/help.lua
@@ -2,51 +2,51 @@ function draw_help_without_mouse_pressed(drawing)
   love.graphics.setColor(0,0.5,0)
   local y = drawing.y+10
   love.graphics.print("Things you can do:", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print("* Press the mouse button to start drawing a "..current_shape(), 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print("* Hover on a point and press 'ctrl+v' to start moving it,", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print("then press the mouse button to finish", 16+30+bullet_indent(),y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print("* Hover on a point or shape and press 'ctrl+d' to delete it", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
+  y = y + math.floor(15*Zoom)
   if Current_drawing_mode ~= 'freehand' then
     love.graphics.print("* Press 'ctrl+f' to switch to drawing freehand strokes", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'line' then
     love.graphics.print("* Press 'ctrl+l' to switch to drawing lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'manhattan' then
     love.graphics.print("* Press 'ctrl+m' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'circle' then
     love.graphics.print("* Press 'ctrl+c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'polygon' then
     love.graphics.print("* Press 'ctrl+g' to switch to drawing polygons", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'rectangle' then
     love.graphics.print("* Press 'ctrl+r' to switch to drawing rectangles", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'square' then
     love.graphics.print("* Press 'ctrl+s' to switch to drawing squares", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   love.graphics.print("* Press 'ctrl+=' or 'ctrl+-' to Zoom in or out", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print("* Press 'ctrl+0' to reset Zoom", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
+  y = y + math.floor(15*Zoom)
   love.graphics.print("Hit 'esc' now to hide this message", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.setColor(0,0.5,0, 0.1)
   love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(Drawing.pixels(drawing.h),y-drawing.y))
 end
@@ -55,56 +55,56 @@ function draw_help_with_mouse_pressed(drawing)
   love.graphics.setColor(0,0.5,0)
   local y = drawing.y+10
   love.graphics.print("You're currently drawing a "..current_shape(drawing.pending), 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   love.graphics.print('Things you can do now:', 16+30,y, 0, Zoom)
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
   if Current_drawing_mode == 'freehand' then
     love.graphics.print('* Release the mouse button to finish drawing the stroke', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   elseif Current_drawing_mode == 'line' or Current_drawing_mode == 'manhattan' then
     love.graphics.print('* Release the mouse button to finish drawing the line', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   elseif Current_drawing_mode == 'circle' then
     if drawing.pending.mode == 'circle' then
       love.graphics.print('* Release the mouse button to finish drawing the circle', 16+30,y, 0, Zoom)
-      y = y+15*Zoom
+      y = y + math.floor(15*Zoom)
       love.graphics.print("* Press 'a' to draw just an arc of a circle", 16+30,y, 0, Zoom)
     else
       love.graphics.print('* Release the mouse button to finish drawing the arc', 16+30,y, 0, Zoom)
     end
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   elseif Current_drawing_mode == 'polygon' then
     love.graphics.print('* Release the mouse button to finish drawing the polygon', 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
     love.graphics.print("* Press 'p' to add a vertex to the polygon", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   love.graphics.print("* Press 'esc' then release the mouse button to cancel the current shape", 16+30,y, 0, Zoom)
-  y = y+15*Zoom
-  y = y+15*Zoom
+  y = y + math.floor(15*Zoom)
+  y = y + math.floor(15*Zoom)
   if Current_drawing_mode ~= 'line' then
     love.graphics.print("* Press 'l' to switch to drawing lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'manhattan' then
     love.graphics.print("* Press 'm' to switch to drawing horizontal/vertical lines", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'circle' then
     love.graphics.print("* Press 'c' to switch to drawing circles/arcs", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'polygon' then
     love.graphics.print("* Press 'g' to switch to drawing polygons", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'rectangle' then
     love.graphics.print("* Press 'g' to switch to drawing rectangles", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   if Current_drawing_mode ~= 'square' then
     love.graphics.print("* Press 'g' to switch to drawing squares", 16+30,y, 0, Zoom)
-    y = y+15*Zoom
+    y = y + math.floor(15*Zoom)
   end
   love.graphics.setColor(0,0.5,0, 0.1)
   love.graphics.rectangle('fill', 16,drawing.y, Drawing_width, math.max(Drawing.pixels(drawing.h),y-drawing.y))
diff --git a/main.lua b/main.lua
index 0856221..ab692e7 100644
--- a/main.lua
+++ b/main.lua
@@ -182,7 +182,7 @@ function keychord_pressed(chord)
     local y = Screen_height
     while y >= 0 do
       if Screen_top_line == 1 then break end
-      y = y - 15*Zoom
+      y = y - math.floor(15*Zoom)
       if Lines[Screen_top_line].mode == 'drawing' then
         y = y - Drawing.pixels(Lines[Screen_top_line].h)
       end
diff --git a/text.lua b/text.lua
index 1b78251..bd51971 100644
--- a/text.lua
+++ b/text.lua
@@ -181,14 +181,14 @@ function Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necess
 end
 
 function Text.scroll_up_while_cursor_on_screen()
-  local y = Screen_height - 15*Zoom -- for Cursor_line
+  local y = Screen_height - math.floor(15*Zoom) -- for Cursor_line
   while true do
     if Screen_top_line == 1 then break end
-    y = y - 15*Zoom
+    y = y - math.floor(15*Zoom)
     if Lines[Screen_top_line].mode == 'drawing' then
       y = y - Drawing.pixels(Lines[Screen_top_line].h)
     end
-    if y < 15*Zoom then
+    if y < math.floor(15*Zoom) then
       break
     end
     Screen_top_line = Screen_top_line - 1
@@ -197,7 +197,7 @@ end
 
 function Text.in_line(line, x,y)
   if line.y == nil then return false end  -- outside current page
-  return x >= 16 and y >= line.y and y < line.y+15*Zoom
+  return x >= 16 and y >= line.y and y < line.y + math.floor(15*Zoom)
 end
 
 function Text.move_cursor(line_index, line, x)
@@ -246,7 +246,7 @@ end
 function Text.cursor_x(line_data, cursor_pos)
   local line_before_cursor = line_data:sub(1, cursor_pos-1)
   local text_before_cursor = love.graphics.newText(love.graphics.getFont(), line_before_cursor)
-  return 25+text_before_cursor:getWidth()*Zoom
+  return 25 + math.floor(text_before_cursor:getWidth()*Zoom)
 end
 
 return Text