This week we'll be talking about one of my favorite franchises of all time,

a core part of my childhood--

Pokemon as shown by the Poke Ball on the screen there.

So back in 1997 I think it was, the first Pokemon

game was released, Red and Blue.

I believe it was released a year earlier in Japan where it

was released as Red, Blue, and Green.

And the overall goal of the game was fairly straightforward.

You were a Pokemon trainer.

Your goal was to go out into the world and try and capture

any number of 151 different types of these creatures called

Pokemon that were based on a whole bunch of different types of creatures.

Shown in the screenshot here, there's a Weepinbell fighting and Geodude.

A Geodude was a rock type, Weepinbeel was a grass type.

You had different types of Pokemon.

When they fight each other, some types were better than other types,

like this sort of very large rock, paper, scissors relationship.

And it was just a very addicting formula.

You'd have a team of these creatures that you had caught and raised

and battled, and you'd fight other trainers.

And the awesome part of this was you could go

and you could actually fight your friends,

or trade Pokemon with your friends that they had caught.

And you would often share stories back and forth

about the different rare creatures that you would have encountered,

and all sorts of things.

You'd have a customized party that was sort of a part of you.

And so this is Pokemon Red.

The series has evolved over time.

This is a screenshot of Gold and Silver, which was released a couple of years

afterwards for the Gameboy Color.

Again, this was released for the regular Gameboy.

Gold and Silver introduced a bunch of new features including breeding,

and a day, night cycle, and a lot of other things

that became part of the core series.

Here is Ruby and Sapphire, which was for the Gameboy Advance

and got a significant graphical update, but the core formula

stayed much the same.

Here is Diamond and Pearl, which is for the DS, which

it made use of two screens, as seen on the top and bottom there.

Here is Black and White, which was another step forward

in that it introduced three dimensional graphics for the over world,

so you could actually see some sort of 3D for the first time in the franchise.

And then more recently, we've seen for the 3DS, games like X and Y,

which is shown here, and Omega Sapphire, Alpha Ruby--

Alpha Sapphire and Omega Ruby, and Moon and Sun.

And so this is a great illustration of why

the RPG genre of video games, role playing game,

even though it's sort of its own unique take on the formula.

But it allows us to, we can sort of dissect this and take a look

at what makes an RPG and what makes a Pokemon game altogether

for a nice cool demonstration.

So today, we'll be talking about a few new things.

We'll be doing things a lot differently in this lecture example

relative to other examples, because we're transitioning away from the state

machine and talking about a construct called the state stack, which

is effectively a more advanced version of the state machine.

Whereas before, we had a state machine that was in one state at a time,

whereby we could be in the play state or the start state or what

not, we can now actually have multiple states

that exist in parallel that are on a stack of data structure, which you've

seen in CS 50 if you've taken, where we can have,

for example, the field state, the play state at the very bottom,

which is always there, and then we can push states onto the stack

as we need to for example, a dialog state

so that we can actually display some dialog,

some text to the screen without getting rid of the play state

that we had there before.

It allows us to render multiple things at the same time,

and then also return back to prior states,

rather than completely create new states every time

we want to make a transition.

We'll be talking about turn based systems.

So an RPGs like Pokemon and others, there

are often battle systems that are usually

turn based in this particular genre where you're fighting-- you have

one team or one character fighting against against one other team or one

other character, and you take turns fighting each other.

And you have an indefinite amount of time to make your decision

and then form some sort of strategy as to how

you want to approach the problem.

We'll be taking a look at a very primitive turn based system,

but a fully functional one today.

Another huge aspect of this genre is graphical user interfaces or GUIs

as they're shortened.

Things like panels, and scroll bars, and text boxes, and menus, all

sorts of these things that allow us to get a more visual sort of look

at our data, and allow us to navigate a much more complex game ecosystem more

efficiently.

And to tie it all together, RPG mechanics at large,

we'll be looking at things like leveling up and experience

and how to calculate the damage that one party does to the other party

throughout the course of a battle.

And so it will be a fairly complicated set of examples,

but fairly illustrative of the genre as a whole.

So I'd like to demonstrate sort of the example that I put together.

If I could get a volunteer from the audience to come up and take a look.

Tony that'd be awesome, thank you so much.

So this is my simple but fully featured, more or less, demonstration of Pokemon.

So if you want to enter or return.

So this is a--

so here we have a--

we can see right off the bat, we have a text box and a play state

like we did before.

So this text box is actually a state that's layered above the place.

So you can see it has some instructions about, if you want to press P,

you can heal your Pokemon.

You can press Enter to dismiss.

So if you go ahead and press Enter, you'll

be able to actually move around now.

And so something to note is before, input was actually

halted while the dialogue was on the top of the screen for the play state.

You're actually not allowed to access or update this bottom state,

because the state stack is only allowing input to the top state.

And so I have limited the play here just to this box,

but if we walk in the tall grass down here, in Pokemon,

in order to actually initiate an encounter

with another Pokemon or another wild Pokemon, you walk in the grass.

So here we've walked in the grass.

There's a random chance for this to happen, there's a 1 in 10 chance

basically.

So it's saying that a wild Bamboon appeared.

So a wild creature appeared.

He's level 5, we're level 5, should be a fairly even battle.

So you can press Enter, and it will say go

the name of your Pokemon, which is an Aardart in this case,

and it's randomly allocated at the moment.

So go ahead and press Enter one more time.

Now we can see on the bottom right, we have a menu.

So we can fight or we can run, so those two choices.

So we can go ahead and fight.

So we fight, whichever Pokemon has the higher

speed will go first and do damage.

We obviously, do a lot more damage, but he's a little bit faster,

so he's going to go first.

So we fight one more time.

We should be able to knock him out.

So as soon as we do, we get a victory message, we get a victory song.

If we press Enter, we'll actually get some experience

for defeating that enemy.

So we've got quite a bit of experience, we got 65 XP.

In that bottom bar, we can see we have all these GUI elements,

we've got a panel here, we have text boxes, we have progress bars,

all these pieces are coming together to give us sort of this turn based system.

And so after this, we may level up just to demonstrate

leveling, which is part of the RPG mechanic side of this game.

So we have to press this one more time.

We did, perfectly.

So they leveled up.

And so now we're level 6, so we can see the 6 changed above our progress bars.

So now will be a little bit stronger every time.

And the stats aren't shown here, it's actually a part of the assignment

is to create a menu that will actually show you how you leveled up,

what stats actually increased.

But underneath the hood, behind the scenes,

you actually are getting stat increases.

And so here we can see that if we our HP goes all the way down to zero,

we faint.

And when we faint, the screen instead of fading to white

will actually fade to black to illustrate the difference

between the two transitions.

And so that we can keep playing indefinitely,

the game will restore your Pokemon back to full health.

And so this will go on forever.

This is effectively what the simulator is, it's just

a simple series of infinite battles.

There are random Pokemon in the grass.

There