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We've covered quite a lot so far. 
You've learned about different forms of 

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primitive data like numbers and strings 
and images. 

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You've learned about expressions like if 
and con, how to define functions and 

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constants, the rules for evaluating DSL 
code. 

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You've also learned the how to design 
functions recipe, the how to design data 

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recipe, and how to use the data-driven 
template rules. 

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You really learned quite a lot. 
But you had to be a certain kind of 

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patient. 
Because the programs we've written so far 

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have been kind of boring. 
A function that consumes a seat number 

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and tells you whether it's on the aisle 
might be useful as part of a big system. 

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But the function itself isn't very 
exciting. 

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That's going to change this week. 
This week we're going to start to get 

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into interactive programs. 
So I mean things like animations, and 

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games, and the kind of desktop 
applications that you might use every 

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day. 
Now, I want to stress something about the 

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way our programs are going to look. 
Here for example, is a fireworks program 

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we might design. 
And what I'm doing is I'm shooting off a 

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bunch of fireworks and they rise into the 
sky and explode beautifully like that. 

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Now, that graphic quality there isn't 
fantastic. 

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It's not Harry Potter Deathly Hallows 
fantastic. 

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That's the way our programs are going to 
look this week. 

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Because graphic quality is something that 
requires a great deal of mass 

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sophistication, and a great deal of 
programming power. 

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So we're going to have simple graphics. 
But the basic structure of our programs, 

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the basic structure of our animations and 
games, and desktop applications. 

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Is really going to be like the same 
structure of the more sophisticated 

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versions. 
So by the end of this week you'll be able 

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to design interactive programs. 
And I'll think you'll also have a better 

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understanding of how some of the programs 
that you use every day work. 

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In fact, project one, which you'll start 
at the end of this week. 

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Is to complete the design of a simple one 
line text editor, kind of like the text 

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editor you use on your phone when you 
want to send a text message.