Sometimes, you don't want a script to start working right from the start of the game. For such cases, you can trigger a script by sending a message, instead of just starting it when the <green flag> button is pressed. This way, the script will stay dormant and inactive until it receives the right message. You can actually compare this to someone yelling a certain order that the script has to respond to. In this section, we will postpone the appearance of the boss monster until certain game conditions are met.

Prepare for lift off

Messages are part of the Events category. Let's go there and see what we have to work with. Near the bottom of the list are three message blocks; one starting block (with the curved top) that can receive a message, and two broadcasters immediately below that can shout a message to all the scripts.