Code not working :-(

A quick bit of messy code,
By the way what are you making?

Graphics 800,600
SetBuffer BackBuffer()


Global world_x = 0
Global world_y = 0

Global world_width = 800
Global world_height = 600


Global grid_x = 0 ;?
Global grid_y = 0 ;?
Global grid_width = 20
Global grid_height = 20


Global tile_size = 50
Global cursor_x = 0 
Global cursor_y = 0





Dim world(world_width-1,world_height-1)

For x=0 To world_width-1
	For y=0 To world_height-1
		world(x,y)=0
	Next
Next



While Not KeyHit(1)
Cls

	user_control
	draw_world
	draw_grid
	
	Flip
	
Wend



Function draw_grid()
	
	Origin -world_x,-world_y
	
	
	For x=0 To grid_width
		For y=0 To grid_height
			Rect grid_x+x*tile_size,grid_y+y*tile_size,tile_size,tile_size,0
			
			
			
		Next
	Next


	Color 0,0,255
	Rect grid_x+cursor_x*tile_size,grid_y+cursor_y*tile_size,tile_size,tile_size,0
	Color 255,255,255
	
	
End Function 



Function draw_world()
	
	Origin -world_x,-world_y
	
	For x=0 To grid_width
		For y=0 To grid_height
			
			If world(x,y)=1 Then 
				Oval grid_x+x*tile_size,grid_y+y*tile_size,5,5
			EndIf
			
			
		Next
	Next

End Function



Function user_control()
	Origin 0,0
	
	If KeyHit(205) And cursor_x<grid_width Then cursor_x = cursor_x + 1
	If KeyHit(203) And cursor_x>0 Then cursor_x = cursor_x - 1
	If KeyHit(200) And cursor_y>0 Then cursor_y = cursor_y - 1
	If KeyHit(208) And cursor_y<grid_height Then cursor_y = cursor_y + 1
	
	If KeyHit(57) Then world(cursor_x,cursor_y)=1
	
	
	;---Scrolling---
	
	If (cursor_x*tile_size)+tile_size-world_x > world_width-70 Then
		world_x=world_x+4
	End If
	
	If (cursor_x*tile_size)-world_x < 70 Then
		world_x=world_x-4
	End If
	
	
	
	If (cursor_y*tile_size)+tile_size-world_y > world_height-70 Then
		world_y=world_y+4
	End If
	
	If (cursor_y*tile_size)-world_y < 70 Then
		world_y=world_y-4
	End If
	
	
	
End Function