We've covered quite a lot so far. 
You've learned about different forms of 
primitive data like numbers and strings 
and images. 
You've learned about expressions like if 
and con, how to define functions and 
constants, the rules for evaluating DSL 
code. 
You've also learned the how to design 
functions recipe, the how to design data 
recipe, and how to use the data-driven 
template rules. 
You really learned quite a lot. 
But you had to be a certain kind of 
patient. 
Because the programs we've written so far 
have been kind of boring. 
A function that consumes a seat number 
and tells you whether it's on the aisle 
might be useful as part of a big system. 
But the function itself isn't very 
exciting. 
That's going to change this week. 
This week we're going to start to get 
into interactive programs. 
So I mean things like animations, and 
games, and the kind of desktop 
applications that you might use every 
day. 
Now, I want to stress something about the 
way our programs are going to look. 
Here for example, is a fireworks program 
we might design. 
And what I'm doing is I'm shooting off a 
bunch of fireworks and they rise into the 
sky and explode beautifully like that. 
Now, that graphic quality there isn't 
fantastic. 
It's not Harry Potter Deathly Hallows 
fantastic. 
That's the way our programs are going to 
look this week. 
Because graphic quality is something that 
requires a great deal of mass 
sophistication, and a great deal of 
programming power. 
So we're going to have simple graphics. 
But the basic structure of our programs, 
the basic structure of our animations and 
games, and desktop applications. 
Is really going to be like the same 
structure of the more sophisticated 
versions. 
So by the end of this week you'll be able 
to design interactive programs. 
And I'll think you'll also have a better 
understanding of how some of the programs 
that you use every day work. 
In fact, project one, which you'll start 
at the end of this week. 
Is to complete the design of a simple one 
line text editor, kind of like the text 
editor you use on your phone when you 
want to send a text message.