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COLTON OGDEN: All right.

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So with Pong 7, we actually
took a big step forward.

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We implemented collision
detection, which

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is a huge buzzword, especially
in game programming.

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But it turns out, it's very simple.

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If you have just simple rectangles
and you're using aligned

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axis bounding box collision
detection, which we were doing,

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or AABB, just a few
lines of code, and now we

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have the ball bouncing
off of our paddles

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and also from the top
and bottom of the screen.

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But you didn't have to use AABB before.

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Fortunately, we can just
check to see whether the y

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value is above or below some amount.

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Now, I realize, actually, also,
in the last couple of examples,

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I've been meaning to add
the love.window.settitle.

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So right now, before I
actually get into this update,

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love.window.settitle of Pong.

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Run it, and it's white again, of course.

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So let's go ahead and change this
down here to 255, 255, 255, and 255.

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Run it, and boom.

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Now we have a functional Pong title.

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So great.

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Told you I was going to do it.

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I knew that someone was going to
comment on it and make fun of me for it,

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and that's totally fine.

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I totally deserve it.

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But anyway, Pong 8, the score update.

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So in this example, we're going to
actually implement adding score.

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So not only do we just
have these static 1

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and 0 on the left, which is fitting
for a computer science class,

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but when the ball goes to the
left and the right of the paddles,

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if it goes beyond the edges,
the right and the left edge,

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we want to increment
the corresponding score.

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So if the ball goes to the
left edge of the screen,

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the right number should
increment, and vice versa.

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If the ball goes past the
right edge of the screen,

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the left number should increment.

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And that's all the slides
we have for this, actually.

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It's going to be a very straightforward,
I think, bit of code here.

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So let's go ahead and implement
this in the update function.

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So let's go up to the very top here.

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So if the game state is play--
now, we are going to have start,

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and we are going to have play.

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And actually, what I want to
do is go to the very bottom.

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I want to delete this game
state equals start thing.

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We don't really need that anymore.

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I'm to go back up here.

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And towards the top, when
we're in the play state--

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I can really do this anywhere,
but I'm going to just put it here.

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So I'm going to say, if the
ball.x is less than or equal to 0,

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then we want the left--

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sorry.

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If the ball is less than 0, we want
the right paddle score to increment.

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So player 2 score should be
equal to player 2 score plus 1.

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Now, you might be looking
at this and thinking

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that this looks a little weird.

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Why are we using player 2 score
equals player 2 score plus 1?

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Can't we use plus equals 1?

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Can't we use plus plus?

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And unfortunately, Lua is a bit
strange in that it doesn't actually

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let you do that shorthand syntax.

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It will only allow you to do the
equals itself plus something.

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There is no shorthand plus equals
or plus plus, unfortunately.

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But we can deal with that.

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Not a terrible inconvenience.

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We're going to do the
same thing for whether it

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goes past the right edge of the screen.

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So if ball.x is greater than or equal
to virtual width minus 4, then--

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and remember, we're accounting for
that size of the rectangle there--

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we're going to say player 1 score
is equal to player 1 score plus 1.

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And I think I have declared
those score variables already,

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which I have indeed done.

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They're set to 0 initially.

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Now, once it is the case that
we have added to the score,

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we want to actually reset the ball.

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So what I can do is I
can say, ball reset,

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and we'll say game state is equal to
start so that we can give them a chance

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to press Enter again once someone has
scored so that it just doesn't happen,

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and they're caught off-guard,
like, oh, we just scored.

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Now the ball's in the
center and it's moving.

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We're going to add that little
layer, that little pressing

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Enter little buffer there.

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So game state is equal to start.

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Save it.

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And then that should be it.

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So let's go ahead, and
let's make sure also

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that we are accounting
in the love.key press

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function for if they press Return.

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Cool.

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So we can have this here.

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This is fine.

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But in reality, all we really need to
do is, if game state is equal to start,

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game state should be equal to play.

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So that's what we're going to do.

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We're going to set that
to end because now we

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don't have to press Enter to
go back to the start state.

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We can just let the ball go
past the left or the right edge.

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So I'm going to go ahead and run this.

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And let's just give it a test.

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Let it bounce off the side.

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I will not purposely do that.

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And perfect.

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It ended getting up one
incremented on the right player

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because it went past the
left edge, which is great.

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So let's go ahead and do it again.

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I'm going to purposefully hit it back.

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Let's just get the other player
to slowly get a point onto them,

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just to make sure that the
left score is working as well.

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Got to try not to do it.

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And perfect.

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So we not only have the
scores incrementing,

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but the ball is getting reset in the
middle of the screen accordingly.

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And we made sure to set the
title in this episode as well.

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So that was it for Pong 8.

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Very simple update-- just
adding the ability to keep

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score on the left and the right side.

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We don't actually have keeping track
of whether one player has won or not.

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We will take care of that soon.

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In the next update, we're
going to actually take

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care of making sure that if player 1
scores, for example, onto player 2,

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player 2 gets to serve the ball
back to player 1 out of fairness.

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We need to keep track of
who actually got scored on

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and then send the ball in the opposite
direction in that circumstance.

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We'll see you for Pong 9.

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