Variables, messages and clones
The three tricks that turn animations into games.
Variables
They store values like points and lives. Create one in Variables > "Make a variable".
Messages
"broadcast" sends a notice to everyone; "when I receive" answers. E.g. the player broadcasts game over and everybody stops.
Clones
"create clone of" makes copies (shots, enemies, rain). Each copy starts at "when I start as a clone". Remember to delete this clone at the end.