An open world is a type of video game level design where a player can roam freely through a virtual world and is given considerable freedom in choosing how or when to approach objectives. The term "free roam" is also used, as is "sandbox" and "free-roaming". "Open world" and "free-roaming" suggest the absence of artificial barriers, in contrast to the invisible walls and loading screens that are common in linear level designs. An "open world" game does not necessarily imply a sandbox. In a true "sandbox", the player has tools to modify the world themselves and create how they play. Generally open world games still enforce some restrictions in the game environment, either due to absolute technical limitations or in-game limitations (such as locked areas) imposed by a game's linearity.