objects/objYourObjectName/

/// objPlayer Create Event
// Initialize player variables

// Movement
move_speed = 4;
direction = 0;

// Stats
health = 100;
max_health = 100;

// State
is_moving = false;

show_debug_message("objPlayer created");

{
  "$GMObject":"",
  "%Name":"objYourObjectName",
  "eventList":[
    {"$GMEvent":"v1","%Name":"","collisionObjectId":null,"eventNum":0,"eventType":0,"isDnD":false,"name":"","resourceType":"GMEvent","resourceVersion":"2.0",},
    {"$GMEvent":"v1","%Name":"","collisionObjectId":null,"eventNum":64,"eventType":8,"isDnD":false,"name":"","resourceType":"GMEvent","resourceVersion":"2.0",},
    {"$GMEvent":"v1","%Name":"","collisionObjectId":null,"eventNum":0,"eventType":3,"isDnD":false,"name":"","resourceType":"GMEvent","resourceVersion":"2.0",},
  ],
  "managed":true,
  "name":"objYourObjectName",
  "overriddenProperties":[],
  "parent":{
    "name":"Objects",
    "path":"folders/Objects.yy",
  },
  "parentObjectId":null,
  "persistent":false,
  "physicsAngularDamping":0.1,
  "physicsDensity":0.5,
  "physicsFriction":0.2,
  "physicsGroup":1,
  "physicsKinematic":false,
  "physicsLinearDamping":0.1,
  "physicsObject":false,
  "physicsRestitution":0.1,
  "physicsSensor":false,
  "physicsShape":1,
  "physicsShapePoints":[],
  "physicsStartAwake":true,
  "properties":[],
  "resourceType":"GMObject",
  "resourceVersion":"2.0",
  "solid":false,
  "spriteId":null,
  "spriteMaskId":null,
  "visible":true,
}

{"id":{"name":"objYourObjectName","path":"objects/objYourObjectName/objYourObjectName.yy",},},

"resources":[
  {"id":{"name":"objInventoryUI","path":"objects/objInventoryUI/objInventoryUI.yy",},},
  {"id":{"name":"objPlayer","path":"objects/objPlayer/objPlayer.yy",},},
  {"id":{"name":"objYourObjectName","path":"objects/objYourObjectName/objYourObjectName.yy",},},
]

// Local variable (function/script scope only)
var _local_var = 100;

// Instance variable (attached to object instance)
instance_var = 50;

// Global variable (accessible everywhere)
global.game_state = "playing";

// ✅ CORRECT
var _result = condition_a ? "foo" : ((condition_b ? "bar" : "baz"));

// ❌ WRONG (will cause compile error in some versions)
var _result = condition_a ? "foo" : condition_b ? "bar" : "baz";

// If statement
if (condition) {
    // code
} else if (other_condition) {
    // code
} else {
    // code
}

// Switch statement
switch (value) {
    case 1:
        // code
        break;
    case 2:
    case 3:
        // code for 2 or 3
        break;
    default:
        // code
        break;
}

// For loop
for (var _i = 0; _i < 10; _i++) {
    show_debug_message(_i);
}

// While loop
while (condition) {
    // code
}

// Repeat loop
repeat (10) {
    // code
}

// With loop (iterate instances)
with (objEnemy) {
    health -= 10;
}

// Create struct (no manual cleanup needed!)
var _player = {
    name: "Hero",
    health: 100,
    max_health: 100,
    level: 1
};

// Access properties
show_debug_message(_player.name); // "Hero"
_player.health -= 10;

// Check if property exists
if (variable_struct_exists(_player, "mana")) {
    // property exists
}

// Dynamic property access
var _prop_name = "health";
var _value = _player[$ _prop_name]; // Same as _player.health

// Create
var _list = ds_list_create();

// Add items
ds_list_add(_list, "apple", "banana", "cherry");
ds_list_insert(_list, 1, "orange"); // Insert at index

// Access
var _item = _list[| 0]; // "apple"
var _size = ds_list_size(_list);

// Iterate
for (var _i = 0; _i < ds_list_size(_list); _i++) {
    show_debug_message(_list[| _i]);
}

// CRITICAL: Always destroy when done!
ds_list_destroy(_list);

// Create
var _map = ds_map_create();

// Add items
_map[? "name"] = "Player";
_map[? "health"] = 100;

// Access
var _hp = _map[? "health"]; // 100

// Check if key exists
if (ds_map_exists(_map, "mana")) {
    // key exists
}

// Iterate
var _key = ds_map_find_first(_map);
while (!is_undefined(_key)) {
    show_debug_message(_key + ": " + string(_map[? _key]));
    _key = ds_map_find_next(_map, _key);
}

// CRITICAL: Always destroy when done!
ds_map_destroy(_map);

/// objPlayer Destroy Event
// Clean up data structures

if (ds_exists(inventory_list, ds_type_list)) {
    ds_list_destroy(inventory_list);
}

if (surface_exists(shadow_surface)) {
    surface_free(shadow_surface);
}

✅ CORRECT:
datafiles/config.json
datafiles/items.json
datafiles/level_data.json

❌ WRONG (may not work in all versions):
datafiles/configs/game_config.json
datafiles/data/items/weapons.json

{"$GMIncludedFile":"","%Name":"config.json","CopyToMask":-1,"filePath":"datafiles","name":"config.json","resourceType":"GMIncludedFile","resourceVersion":"2.0",},

// Load JSON from datafiles/
function load_json_file(_filename) {
    if (!file_exists(_filename)) {
        show_debug_message("ERROR: File not found: " + _filename);
        return noone;
    }

    var _file = file_text_open_read(_filename);
    var _json_string = "";
    while (!file_text_eof(_file)) {
        _json_string += file_text_read_string(_file);
        file_text_readln(_file);
    }
    file_text_close(_file);

    return json_parse(_json_string);
}

// Save JSON to working directory
function save_json_file(_filename, _data) {
    var _json_string = json_stringify(_data);
    var _file = file_text_open_write(_filename);
    file_text_write_string(_file, _json_string);
    file_text_close(_file);
}

// Working directory (platform-dependent save location)
var _save_path = working_directory + "savegame.json";

// Game save ID (unique folder for your game)
// On Windows: %LOCALAPPDATA%/[game_save_id]/
var _save_id = game_save_id;

// rmGameplay Room Creation Code
// Clear handlers to prevent duplicates
global.input_controller.clear_all_handlers();

// Register handlers fresh
global.input_controller.register_handler("ACTION", function(_cmd) {
    // handle action
});

// Draw sprite
draw_sprite(spr_player, image_index, x, y);
draw_sprite_ext(spr_player, image_index, x, y, scale_x, scale_y, rotation, color, alpha);

// Draw text
draw_text(x, y, "Hello World");
draw_set_font(fnt_arial);
draw_set_color(c_white);
draw_set_halign(fa_center);
draw_set_valign(fa_middle);

// Draw shapes
draw_rectangle(x1, y1, x2, y2, outline);
draw_circle(x, y, radius, outline);
draw_line(x1, y1, x2, y2);

// Create surface
if (!surface_exists(shadow_surface)) {
    shadow_surface = surface_create(room_width, room_height);
}

// Draw to surface
surface_set_target(shadow_surface);
draw_clear_alpha(c_black, 0);
// ... draw operations ...
surface_reset_target();

// Draw surface to screen
draw_surface(shadow_surface, 0, 0);

// CRITICAL: Free surface when done
if (surface_exists(shadow_surface)) {
    surface_free(shadow_surface);
}

// Send GET request
var _request_id = http_get("https://api.example.com/data");

// In Async HTTP event
var _id = async_load[? "id"];
if (_id == _request_id) {
    var _status = async_load[? "status"];
    if (_status == 0) {
        var _result = async_load[? "result"];
        var _data = json_parse(_result);
        // Process data
    }
}