diff --git a/.github/workflows/luacheck.yml b/.github/workflows/luacheck.yml
index 32ded65..d9d6abf 100644
--- a/.github/workflows/luacheck.yml
+++ b/.github/workflows/luacheck.yml
@@ -18,4 +18,4 @@ jobs:
     - name: Setup ‘luacheck’
       run: luarocks install luacheck
     - name: Run ‘luacheck’ linter
-      run: lua luacheck.lua .
+      run: cd util; lua luacheck.lua
diff --git a/luacheck.lua b/util/luacheck.lua
similarity index 94%
rename from luacheck.lua
rename to util/luacheck.lua
index e86d4ba..141e18b 100755
--- a/luacheck.lua
+++ b/util/luacheck.lua
@@ -2,7 +2,7 @@ local exec = os.execute
 local fmt, find, sub = string.format, string.find, string.sub
 local var = "[%w%.%[%]\"\'_]"
 
-exec("reset")
+exec "clear"
 
 local function split(str, delim, include_empty, max_splits, sep_is_pattern)
 	delim = delim or ","
@@ -121,10 +121,10 @@ for _, p in ipairs(files) do
 		_file:close()
 	end
 
-	_load("./src/" .. p .. ".lua")
+	_load("../src/" .. p .. ".lua")
 end
 
-exec("luacheck init.lua")
-exec("luacheck ./src/operators.lua")
-exec("luacheck ./src/*.l")
-exec("rm ./src/*.l")
+exec "luacheck ../init.lua"
+exec "luacheck ../src/operators.lua"
+exec "luacheck ../src/*.l"
+exec "rm ../src/*.l"
diff --git a/util/optipng.sh b/util/optipng.sh
new file mode 100644
index 0000000..4e59b44
--- /dev/null
+++ b/util/optipng.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Colors with 0 alpha need to be preserved, because opaque leaves ignore alpha.
+# For that purpose, the use of indexed colors is disabled (-nc).
+
+cd ../textures
+find -name '*.png' -print0 | xargs -0 optipng -o7 -zm1-9 -nc -strip all -clobber
diff --git a/util/servers.lua b/util/servers.lua
new file mode 100644
index 0000000..abd06a7
--- /dev/null
+++ b/util/servers.lua
@@ -0,0 +1,23 @@
+local JSON = require"JSON" -- luarocks install json-lua
+os.execute "clear"
+
+local list = io.popen("curl -s -H 'Accept: text/html' http://servers.minetest.net/list"):read("*a")
+      list = JSON:decode(list).list
+
+local servers = {}
+
+for _, server in ipairs(list) do
+	if server.mods then
+		for _, mod in ipairs(server.mods) do
+			if mod == "i3" then
+				table.insert(servers, server.name)
+			end
+		end
+	end
+end
+
+if #servers > 0 then
+	print(("=> %u/%u servers using [i3]:\n\t• %s"):format(#servers, #list, table.concat(servers, "\n\t• ")))
+else
+	print"No server using [i3]"
+end