nderMap.fillStyle = "#fff"
    underMap.fillRect(0, 0, 200, 200)
    underMap.fillStyle = "#444"
    for i in range(len(arena)):
        for j in range(len(arena[i])):
            if arena[i][j]:
                underMap.fillRect(i * 8, j * 8, 8, 8)

def init():
    global canvas, overlay, map, mpos
    ele = doc["map"]
    if not ele.getContext:
        alert('An error occured creating a Canvas 2D context. '
            'This may be because you are using an old browser')
        return
    map = ele.getCon