The Alarm Event in GameMaker: Studio
Alarms are excellent for when you want to time Actions in your game in GameMaker: Studio. For example, if you want the player to only shoot bullets once every two seconds, you can set an Alarm for that. If you want to time when new enemy planes appear, you can set an Alarm for that as well.
You can add up to 12 Alarms for each Instance in the Room. To get an Alarm to work, you must first set an Alarm Action to trigger the Alarm Event after a countdown that you set. In that way, Alarms enable you to time when events happen in your game.
Timelines are another great way to time events in your game.
When you choose the Alarm Event from the Event menu, a new submenu opens. From that submenu, you can choose the Alarm you want to configure and add Actions to (see this figure).
An Instance is an Object that you’ve placed in the Room. You can place more than one Instance of an Object in a Room, so you can have multiple Instances of the same Object in your game.