Basic Tile Collision

Rafael's link is better documented than this.

In fact this following code was adapted from some guy's on Blitzcoder - I couldn't get my head round his, so I kind of taught myself through his - if that makes sense.

If you want me to comment it, I might.

Graphics 640,480,32,2
SetBuffer BackBuffer()

Dim map(19,19)

Global px=20
Global py=20
Global gpx,gpy

readmap()

While Not KeyHit(1)
    Cls

    drawmap()
    checkmove()
    drawplayer()
    showstats()

    Flip
Wend
End


; FUNCTIONS


; Player Map Collision
Function playermapcollision()
    For x=-1 To 1
        For y=-1 To 1
            If map(gpx+x,gpy+y)=1
                If RectsOverlap (px,py,20,20,((px/20)*20)+x*20,((py/20)*20)+y*20,20,20) Then Return True
            End If
        Next
    Next
End Function

; Show Stats
Function showstats()
    Text 430,10,"Grid Ref: "+gpx+","+gpy
   
    Text 430,30,map(gpx-1,gpy-1)+" "+map(gpx,gpy-1)+" "+map(gpx+1,gpy-1)
    Text 430,40,map(gpx-1,gpy)+" "+map(gpx,gpy)+" "+map(gpx+1,gpy)
    Text 430,50,map(gpx-1,gpy+1)+" "+map(gpx,gpy+1)+" "+map(gpx+1,gpy+1)

End Function

; Check Move
Function checkmove()
   
    ox=px
    oy=py
   
    If KeyDown(205)
        px=px+2
    End If
   
    If KeyDown(203)
        px=px-2
    End If
   
    If KeyDown(200)
        py=py-2
    End If
   
    If KeyDown(208)
        py=py+2
    End If
   
    If px>360 Or px<20 Then px=ox
    If py>360 Or py<20 Then py=oy
   
    gpx=px/20
    gpy=py/20
   
    If playermapcollision() = True Then px=ox:py=oy
   
End Function

; Draw Player
Function drawplayer()
    Rect px,py,20,20
End Function

; Draw Map
Function drawmap()
    For ac=0 To 19
        For dn=0 To 19
            Color 0,0,255
            If map(ac,dn)=1 Then Rect ac*20,dn*20,20,20
            Color 0,255,0
            Line ac*20,0,ac*20,400
            Line 0,dn*20,400,dn*20
            Color 255,255,255
        Next
    Next
End Function

; Read Map
Function readmap()
    Restore level1
    For dn=0 To 19
        For ac=0 To 19
            Read a
            map(ac,dn)=a
        Next
    Next
End Function

.level1
Data 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1
Data 1,0,0,0,1,0,0,0,0,0,1,1,1,1,1,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
Data 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1