 How many numbers are there? How about strings or images? All of the types of data you've seen so far have infinite variations, which allows for a lot of variety in your programs. But sometimes you just need a simple yes or no, true or false, and there's actually a type just for that. A boolean is a type of data that can only have one of two possible values, true or false. That makes them really well suited to answer simple true or false questions for our program, such as 3 is less than 4, which we could speak as is 3 less than 4. The value that returns is true since 3 is less than 4. Booleans are useful for comparing things. We can ask if one number is less than another, if two strings are equal, and so on. Equal functions like less than, greater than, and equal all take two numbers as their domain and produce a boolean as their range by comparing the two numbers. Sometimes we want to compare values in more complex ways. For example, asking if a player's x coordinate is greater than zero and less than 100, or if a string equals up or down. And even if a number is not 42, these blocks and or and not allow us to modify and combine booleans to answer more complex and interesting logical questions. In this stage, you'll need to write boolean functions to make sure that the sprites in a game follow the rules that you set out for them, such as not going off the side of the screen. Thanks for watching. Bye.