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INSTRUCTOR: So today, we start on project 4, which is,

as you know, the big project.

And Helen is going to do a walkthrough of the project,

and the code, and the organization,

because this is a pretty big sized project.

It's got about 4,500 lines of code.

And it's not code that is kind of like simple code.

It's all content-bearing code.

So I think having a bit of an orientation to it,

more than we give for the other codes that you work,

on which are pretty small, this will be great.

So, Helen, take it away.

HELEN XU: Hi, everyone.

Can you hear me?

Awesome, so today we're going to be doing the walkthrough

for the final project.

You can look at the code and clone it publicly here.

And please remember to fill up your team's by 7:00 PM today,

so we can populate the list and get your repos.

Yeah, and if there are any issues accessing this,

just let me know.

Or put it on Piazza and then we can fix it.

So we just had a game of Lesierchess.

But in case you missed it, we'll go

into more details about what the game actually does.

So first, we're going to go through the game rules.

So you saw that there are these pieces.

There's these triangles.

And there's kings.

So the triangles are pawns.

And the kings, they look like crowns.

And there are two teams.

There's orange and lavender, or tangerine and lavender.

And each side starts out with seven pawns and one king.

And this is the starting position.

So you can see like the kings are in the corner.

And they're just lined up like in the middle.

And each piece has four orientations.

So you can see that the pawn is up, down, left, right.

And then the king is also like that.

And in general, the game starts with tangerine moving first.

And then the play alternates between the two players.

Each piece moves the same, whether it's king or pawn.

And each turn has two parts.

So you saw the demo.

But you move first.

When you pick one of your pieces, and you move first.

And then at the end, your King has to fire the laser.

And the laser reflects off the long edge of the pawn.

And they'll kill the pawn if it shoots the short edges.

And one side wins when the king gets shot,

or when the opposing king gets shot, whether by themselves

or by your own king.

And so I talked a little about moving.

And at the beginning of each turn, the player to move

chooses a piece to move.

And you can move your King or any of your pawns.

And there are two types of moves.

There's basic moves, and swat moves.

And basic moves are just, basically, shifts or rotations.

So in the example, you can rotate 90, 180, or 270 degrees.

So in the top, row you just rotate.

This is the example of moving a pawn.

So you rotate your pawn.

Or you can move to an empty adjacent square.

So those are the bottom two rows.

And there are eight adjacent squares in this example.

So there are eight shifts.

But there would be less than eight

if you were, for example, like at the edge of the board.

And on a move, you can either shift or rotate.

But you can't do both.

There are also these swap loops.

So if you're adjacent to an opposing piece,

you can switch with them.

And then you have to make another basic move

after that, that is not a swap.

So, basically, you can either--

and it has to be with that same piece

that you just swapped with.

So you just either shift or rotate.

Is everyone good on the rules?

Just a couple more things.

So there's this Ko rule, which is

from Go, which ensures that the game makes progress.

So it makes a move illegal if it undoes the opponent's most

recent move by just moving back to where you just were.

So this is an example.

Let's say you're tangerine.

And you swapped with the purple one right next to you.

And then you shifted left and bottom.

And so lavender can return by swapping back

with your orange piece, and shifting again.

But this is actually, illegal because now

you just got to your original position.

So you're not allowed to just keep cycling back and forth.

And so a draw occurs if there have been 50 moves by each side

without a pawn being zapped, the same position

repeats itself by the side on move,

or the two players agree to a draw.

So just kind of like in chess, a chess clock

limits the amount of time the players have to make a move.

So you can't just keep competing indefinitely.

When it's your moves, your clock counts down.

When it's your opponent's moves, your clock stops.

So it's not counting your time.

And we used Fisher time control.

There's a picture of Bobby Fisher, who

made it, up which used an initial time budget and a time

increment.

So in this example, there's fis60 and 0.5,

which means that, in the beginning,

each player has 60 seconds.

And you get to use the 60 seconds however you want.

And when you end your move, you get 0.5 extra seconds.

But the 60 and 0.5 could be anything.

That's just an example.

So we'll go into an example of how you actually

play this game.

For a king to zap the enemy king,

it risks opening itself to counter-attack.

So look at this example.

And how can tangerine zap the lavender pawn in F5,

by moving one of its pieces?

AUDIENCE: [INAUDIBLE]

HELEN XU: Move C4.

AUDIENCE: Tangerine, that's lavender.

HELEN XU: You're tangerine in this example.

And you're trying to zap the one on F5.

Yep?

AUDIENCE: You move the tangerine piece at E22 to F1.

HELEN XU: E2 to F1.

Oh, sorry, by zap, it means shoot the backside.

That would shoot the long side.

Good point.

Yeah, so you're trying to kill the piece on F5.

AUDIENCE: [INAUDIBLE]

HELEN XU: Yeah, exactly.

So in this, you can move C2 to B1, as you just said.

And then you draw the path.

And you can see that you've just killed--

or if you're tangerine, you've just killed the piece at F5.

Now, how can lavender counter?

By counter, we mean lavender can win

the game from this position.

AUDIENCE: Is it A4 to A3?

HELEN XU: A4 to A3.

No, I don't think so.

Yep?

AUDIENCE: [INAUDIBLE]

HELEN XU: Sorry, what?

King, like the orange one?

Oh, the lavender one.

You're trying to shoot the orange king.

Oh, yes, you're right.

You can, actually.

Yes, good, that's not the one that we had,

but apparently there are two ways.

Good.

So if you notice you could also--

that's another way to get that path.

But you can also move one of the pawns.

Cool, so this is just pointing out

one of the subtleties of the game, which is you