Your first script

Make the script

In Studio, open the Scripts window and press New script. It makes scripts/script1.lua with a starting point. Every .lua in scripts/ goes into the pack.

Greet the player

jfg.on("level", function(level)
  jfg.log("entered level", level)
  jfg.message("Welcome! D-pad up for health.", 4)
end)

jfg.on("level", fn) runs once when a level’s objects are set up. jfg.log writes to bin/jfg_mods.log; jfg.message shows a line on screen.

React to a button

jfg.on("tick", function(level, seconds)
  if jfg.pressed("DUP") then
    local x, y, z = jfg.player()
    if x then
      local ok, why = jfg.spawn(0xA9, x + 60, y + 10, z)   -- 0xA9: a health pickup
      if not ok then jfg.log("spawn failed:", why) end
    end
  end
end)

tick runs every game tick in a level. jfg.pressed is true on the tick the button went down. jfg.spawn creates an object as if it were in the level’s list (at most 64 per level).

Open a door from a spot

local opened = false
jfg.on("level", function() opened = false end)
 
jfg.on("tick", function(level)
  if opened or level ~= jfg.level_id("level1") then return end
  local x, y, z = jfg.player()
  if x and math.abs(x - 500) < 100 and math.abs(z - 800) < 100 then
    opened = true
    jfg.unlock_door(1)
    jfg.message("Something opened in the distance...", 4)
  end
end)

level1 is the name of a level in your project; jfg.level_id turns it into the number the port gave it this run. Door id 1 is the doorId field of a door in that level.

Save and play

Save script, then Play. If something doesn’t happen, look in bin/jfg_mods.log: errors name the script and line, and a handler that fails is switched off (the game keeps running).