TileMap Array and only drawing whats on screen?

I came up with my own noob way of doing it thanks to understanding what tonyg was doing.

Code here if anyone wants it.

SuperStrict

Graphics 800, 600

Global MapWidth:Int = 1600 / 25
Global MapHeight:Int = 1600 / 25

Global MapStartX:Int = 50
Global MapSTartY:Int = 50

Global MapXOffset:Int, MapYOffset:Int

Global array:Int[MapWidth, MapHeight] 

Print MapWidth

For Local x:Int = 0 Until MapWidth
	For Local y:Int = 0 Until MapHeight
		array[x, y] = Rand(0, 5) 
	Next
Next

Global startmapx:Int = 0, startmapy:Int = 0

While Not KeyHit(KEY_ESCAPE) 
	Cls
		
		DrawMap() 
		MoveMap() 
		
	Flip
Wend

Function MoveMap() 
	If KeyHit(KEY_LEFT) 
		If startmapx <= 0
			startmapx = 0
			MapStartX = 50
		Else
			MapXOffset:-1
			startmapx:-1
			MapStartX:+25
		EndIf
	ElseIf KeyHit(KEY_RIGHT) 
		If startmapx < MapWidth - 28
			MapXOffset:+1
			startmapx:+1
			MapStartX:-25
		Else
			startmapx = MapWidth - 28
		End If
	End If
	
	If KeyHit(KEY_UP) 
		If startmapy <= 0
			startmapy = 0
			MapSTartY = 50
		Else
			MapYOffset:-1
			startmapy:-1
			MapSTartY:+25
		EndIf
	ElseIf KeyHit(KEY_DOWN) 
		If startmapy < MapHeight - 20
			MapYOffset:+1
			startmapy:+1
			MapSTartY:-25
		Else
			startmapy = MapHeight - 20
		EndIf
	End If
	
End Function


Function DrawMap() 
	Local endmapx:Int, endmapy:Int
		
	If MapXOffset + 25 > MapWidth
		endmapx=mapwidth
	Else
		endmapx = MapXOffset + 28
	EndIf
	If MapYOffset + 20 > MapHeight
		endmapy=mapheight
	Else
		endmapy = MapYOffset + 20
	EndIf
	
	
	For Local x:Int = startmapx Until endmapx
		For Local y:Int = startmapy Until endmapy
			Select array[x, y] 
				Case 0
					SetColor 255, 255, 255
					DrawRect MapStartX + x * 25, MapSTartY + y * 25, 25, 25
				Case 1
					SetColor 0, 255, 255
					DrawRect MapStartX + x * 25, MapSTartY + y * 25, 25, 25
				Case 2
					SetColor 255, 0, 255
					DrawRect MapStartX + x * 25, MapSTartY + y * 25, 25, 25
				Case 3
					SetColor 255, 255, 0
					DrawRect MapStartX + x * 25, MapSTartY + y * 25, 25, 25
				Case 4
					SetColor 0, 0, 255
					DrawRect MapStartX + x * 25, MapSTartY + y * 25, 25, 25
			End Select
		Next
	Next
End Function