function generateGround()
    -- some constants here
    local minX = 0
    local maxX = 100
    local minY = 0
    local maxY = 100
    local defaultGroundTexture = "textures/tiles/ground"
    local defaultAirTexture = "textures/tiles/stone"

    -- function start
    local defaultElevationValue = (maxY + minY) / 2
    local getNearestHigherPo2 = function(n) local val = 2; while val < n do val = val * 2; end; return val; end
    local adaptedGroundWidth = getNearestHigherPo2(1 + maxX - minX)

    -- this table will contain, for each integral x coord, the height of the floor
    local requestedFloorLevels = {}
    for x = 0, adaptedGroundWidth, 1 do requestedFloorLevels[x] = defaultElevationValue; end        -- filling the table with default elevation

    -- loop that fills requestedFloorLevels
    local step = adaptedGroundWidth / 2
    while step >= 1 do
        local stepLog = math.log(step)
        for x = step, adaptedGroundWidth - 1, step * 2 do
            local averageValue = (requestedFloorLevels[x - step] + requestedFloorLevels[x + step]) / 2
            local elevationDelta = (math.random() - 0.5) * stepLog * 2
            requestedFloorLevels[x] = averageValue + elevationDelta
        end
        step = step / 2
    end

    -- loop that will create all entities
    for x = 0, maxX - minX, 1 do
        local realX = x + minX
        local groundElevation = math.floor(requestedFloorLevels[realX] + 0.5)

        local leftGroundElevation = defaultElevationValue
        if x ~= 0 then leftGroundElevation = math.floor(requestedFloorLevels[realX - 1] + 0.5); end
        local rightGroundElevation = defaultElevationValue
        if realX ~= maxX then rightGroundElevation = math.floor(requestedFloorLevels[realX + 1] + 0.5); end

        for y = minY, maxY, 1 do
            local entity = Entities:new()
            entity:add("position")
            entity.position.x, entity.position.y = realX, y

            entity:add("tileDisplay")

            if y < groundElevation then
                entity.tileDisplay.textureBottom = defaultGroundTexture
                entity.tileDisplay.textureUp = entity.tileDisplay.textureBottom

            elseif y == groundElevation then

                entity.tileDisplay.textureBottom = defaultGroundTexture
                if leftGroundElevation > groundElevation then
                    entity.tileDisplay.textureUp = defaultAirTexture
                    entity.tileDisplay.leftGoesUp = true
                elseif rightGroundElevation > groundElevation then
                    entity.tileDisplay.textureUp = defaultAirTexture
                    entity.tileDisplay.leftGoesUp = false
                else
                    entity.tileDisplay.textureUp = entity.tileDisplay.textureBottom
                end

            else
                entity.tileDisplay.textureBottom = defaultAirTexture
                entity.tileDisplay.textureUp = defaultAirTexture
            end
        end
    end
end

generateGround()