diff --git a/maps/dungeons/biome_dirtlands.lua b/maps/dungeons/biome_dirtlands.lua
index 3a1cedd3..f4b905ff 100644
--- a/maps/dungeons/biome_dirtlands.lua
+++ b/maps/dungeons/biome_dirtlands.lua
@@ -53,8 +53,8 @@ end
 
 local function dirtlands(surface, room)
     local dungeontable = DungeonsTable.get_dungeontable()
-    max_spawn = math.floor(dungeontable.depth[surface.index] / 8)
-    max_worm = max_spawn + 1
+    local max_spawn = math.floor(dungeontable.depth[surface.index] / 8)
+    local max_worm = max_spawn + 1
     local path_tile = 'dirt-' .. math_random(1, 3)
     for _, tile in pairs(room.path_tiles) do
         surface.set_tiles({{name = path_tile, position = tile.position}}, true)
diff --git a/maps/dungeons/functions.lua b/maps/dungeons/functions.lua
index 9a8e263c..e5a3d1ba 100644
--- a/maps/dungeons/functions.lua
+++ b/maps/dungeons/functions.lua
@@ -363,18 +363,6 @@ end
 --
 -- 1000 science (all types) = 9822 coal, 13492 stone, 48736 copper, 63018 iron
 --                            20         27           98            127 max-stones
-local function get_ore_amount_old(surface_index)
-    local scaling = game.forces.player.mining_drill_productivity_bonus
-    local amount = 5000 * Public.get_dungeon_evolution_factor(surface_index) * (1 + scaling)
-    if amount > 500 then
-        amount = 500
-    end
-    amount = math_random(math_floor(amount * 0.7), math_floor(amount * 1.3))
-    if amount < 1 then
-        amount = 1
-    end
-    return amount
-end
 
 local function get_ore_amount(surface_index)
    local d = DungeonsTable.get_dungeontable()
@@ -440,7 +428,7 @@ function Public.rocky_loot(event)
     end
     local player = game.players[event.player_index]
     local amount = math.ceil(get_ore_amount(player.surface.index))
-    local rock_mining = {}
+    local rock_mining
     local floor = player.surface.index - DungeonsTable.get_dungeontable().original_surface_index;
     if floor < 10 then
        -- early game science uses less copper and more iron/stone
diff --git a/maps/dungeons/research.lua b/maps/dungeons/research.lua
index ee81a270..3002c4c7 100644
--- a/maps/dungeons/research.lua
+++ b/maps/dungeons/research.lua
@@ -75,12 +75,12 @@ function Fixed.Init()
     end
 end
 
-local function get_surface_research(index) 
+local function get_surface_research(index)
    return locked_researches[floor_num(index)]
 end
 
 function Fixed.techs_remain(index)
-   local tech = get_surface_research(index) 
+   local tech = get_surface_research(index)
    if tech and game.forces.player.technologies[tech].enabled == false then
       return 1
    end
@@ -104,6 +104,11 @@ function Fixed.room_is_lab(index)
    return tech and game.forces.player.technologies[tech].enabled == false
 end
 
+function Fixed.noop()
+end
+
+Fixed.noop() -- eliminate luacheck warning
+
 -- Variant 2, all research needs unlocking, several can be found on each floor
 -- and the research is semi-randomly distributed. Research packs occur at the
 -- first half of the ranges.
@@ -357,7 +362,7 @@ function Variable.calculate_distribution()
    table.shuffle_table(all_research)
    local technologies = game.forces.player.technologies
    for i = 1, #all_research do
-      v = all_research[i]
+      local v = all_research[i]
       local floor1 = math.random(v.min, v.max)
       local floor2 = math.random(v.min, v.max)
       local res1 = get_research_by_floor(floor1)
@@ -505,4 +510,9 @@ function Variable.room_is_lab(index)
    return rooms_opened(index) >= res[1].room
 end
 
+function Variable.noop()
+end
+Variable.noop() -- eliminate luacheck warning if return Fixed is used
+
+-- return Fixed
 return Variable
diff --git a/maps/dungeons/tiered_dungeon.lua b/maps/dungeons/tiered_dungeon.lua
index 12a8f374..6fe2cee3 100644
--- a/maps/dungeons/tiered_dungeon.lua
+++ b/maps/dungeons/tiered_dungeon.lua
@@ -56,11 +56,11 @@ local disabled_for_deconstruction = {
 }
 
 local function enable_hard_rooms(position, surface_index)
-    dungeon_table = DungeonsTable.get_dungeontable()
-    floor = surface_index - dungeon_table.original_surface_index
+    local dungeon_table = DungeonsTable.get_dungeontable()
+    local floor = surface_index - dungeon_table.original_surface_index
     -- can make it out to ~200 before hitting the "must explore more" limit
     -- 140 puts hard rooms halfway between the only dirtlands and the edge
-    floor_mindist = 140 - floor * 10
+    local floor_mindist = 140 - floor * 10
     if floor_mindist < 80 then -- all dirtlands within this
        return true
     end
diff --git a/modules/changelog.lua b/modules/changelog.lua
index b8fe9690..4985b642 100644
--- a/modules/changelog.lua
+++ b/modules/changelog.lua
@@ -1,5 +1,4 @@
 local Event = require 'utils.event'
-local Global = require 'utils.global'
 local Tabs = require 'comfy_panel.main'
 local SpamProtection = require 'utils.spam_protection'
 local Token = require 'utils.token'
diff --git a/modules/melee_mode.lua b/modules/melee_mode.lua
index 9777d320..3105d9a3 100644
--- a/modules/melee_mode.lua
+++ b/modules/melee_mode.lua
@@ -88,8 +88,8 @@ local function change_to_ranged(player)
    if main_inv == nil or gun_inv == nil or ammo_inv == nil then
       return false
    end
-   local gun_moved = try_move_from_main(main_inv, gun_inv, moved.gun)
-   local ammo_moved = try_move_from_main(main_inv, ammo_inv, moved.ammo)
+   try_move_from_main(main_inv, gun_inv, moved.gun)
+   try_move_from_main(main_inv, ammo_inv, moved.ammo)
    state[player.index] = {}
    return true
 end