-- Iterate over every tile in the new chunk and spam with random resources, if empty and possible.
script.on_event(defines.events.on_chunk_generated, function (event)
    -- this mod is intended as an early game challenge. Therefore do nothing on any non-initial surface.
    if not (event.surface.index == 1) then return end

    -- prevent one big continuous patch
    if (event.area.left_top.x/32)%10 == 5 or (event.area.left_top.y/32)%10 == 5 then
        return
    end

    -- dont spam uranium as it will halt normal miners :/
    ores = {"stone", "iron-ore", "copper-ore", "coal"}
    for x=event.area.left_top.x+0, event.area.right_bottom.x-1 do
        for y=event.area.left_top.y+0, event.area.right_bottom.y-1 do
            if  event.surface.get_tile(x, y).collides_with("ground_tile")
                and #event.surface.find_entities_filtered{area={{x,y}, {x+1, y+1}}, type="resource"} == 0
                and #event.surface.find_entities_filtered{area={{x-1, y-1}, {x+1, y+1}}, name="cliff"} == 0
            then
                cnt = math.random(20, 50)
                ore = math.random(1, 4)
                event.surface.create_entity({name=ores[ore], amount=cnt, position={x, y}})
            end
        end
    end
end)