Lua is simple on the surface, but extremely powerful underneath.
This article explores metatables, metamethods, coroutines, advanced module design, and a set of practical patterns used in games, tools, and embedded systems.

All examples are fully runnable with standard Lua 5.3/5.4.

1. Metatables: Lua’s Custom Behavior Engine

Metatables let you customize how tables behave—similar to operator overloading, custom indexing, inheritance, and more.

1.1 Basic Example: __index Fallback

local defaults = {hp = 100, mp = 50}

local player = {}
setmetatable(player, {
  __index = defaults
})

print(player.hp)  -- 100
print(player.mp)  -- 50

Explanation: