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In this lecture, we're making our enemy move and we're making our enemy flip direction.

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When they fly and bump into the wall, they'll head the other direction.

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So let's get started.

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Let's kick off by creating a new script in our scripts folder.

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Right click, create a C-sharp script and we'll call this C sharp script.

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Enemy movement, open up enemy movement.

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Just get rid of the stuff we don't need the couple of comments that we're absolute legends by now,

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so we don't need to know those comments, just wasted space.

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What we do need to do is to access the rigid body, because a rigid body is how we move things around

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in the world.

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So as we usually do, we're going to create a reference for rigid body 2D, which will be type and we'll

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call it my rigid body semicolon.

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While we're here.

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I'd also like some way of us being able to have a variable to serialize the speed of the enemy.

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So I'm going to create a new float and I'll do a serialized field before that.

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Actually, that'd be wise, serialized, filled float.

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We'll call this move speed and I'll initialize that.

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And just straight up one F as a starting point, let's just get the enemy moving across the screen,

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just just going from left to right, doing a bit of a move.

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So an update we will access my rigid body dot velocity.

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We've done this before with the player and that's going to equal what a little micro challenge for you

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here.

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It's going to equal new vector two and in parentheses we want move speed because this is on the x y

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axis not move input, move speed x y excess comma zero because we don't want it to be doing any ups

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and downs.

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So we'll save that back over into unity.

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We better add that script to the enemy so it knows what's going on.

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Enemy and then just drag the enemy movement script over onto the enemy.

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There we go, click on play actually to make this a little bit more hilarious because I think I know

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what's going to happen.

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We'll put the enemy over on the left, but the player on the right, the enemy should be moving from

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left to right of screen.

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It's not.

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We've done something wrong.

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Oh, goodness me.

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My apologies.

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If you knew this and you were yelling at me, yelling at the screen, I could edit out my mistake,

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but.

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Oh, why not?

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We'll leave Rick as being a bit of a numpty.

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So what have we missed in here?

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We've missed getting the component.

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My rigid body equals get component.

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Rigid body to dx parentheses semicolon.

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There we go.

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That's a step that we missed.

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Thank you.

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And apologies if you knew that already.

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If you didn't spot it.

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Not to worry, I didn't spot it.

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Moving too quick, moving with too much velocity.

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So click on play now.

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We'll see if our hilarious thing happens with the enemies bouncing across the screen.

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Gets the player, hey player, let's go for a little bit of a ride.

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Our center machine camera's moving along with it and he's going to say, Let's just drop you off the

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cliff.

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Not a problem.

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I thought it was funny, but in hindsight it actually wasn't overly hilarious.

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But let's move to the next stage, which is to get our enemy running down there, hitting the wall and

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then turning around.

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That was a pretty slow journey.

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So we'll put the enemy really close for this and we want to make sure the enemy is touching right on

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top of the ground.

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Now, there's a little technique.

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I was going to give this to you as a challenge, but it's a bit sneaky because it's a tough one to figure

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out.

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Or at least it took me a while to figure out.

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I'm going to show you how we'll make the enemy turn.

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And then if you're ready to add the code yourself, you can.

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What we need to do on the enemy is add another component, yet another component which will be a box

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collider 2d a little bit the way the player had feet in addition to this, this capsule that's going

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to be the capsule is going to be for when it's player to enemy collision.

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But this box collider that we're about to add is going to be for should I turn around yet so box collider

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two DD We'll get in there and edit that a little bit using the edit collider What I want to do is make

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a reverse periscope.

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What does that even mean?

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Well, you know, in submarines, how they have a periscope that sticks up out of the ground and you

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can see something above the water.

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We're doing it the other way around, which is this is going to be underground underneath here.

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Put it back a little bit.

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We want to have the we want to have it fairly narrow.

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So what's going to happen here?

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Let me explain.

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Is that goober just w to movie?

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It's going to bounce along.

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Bounce, bounce, bounce, bounce.

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We're going to use on Collision Exit, which means currently there's collision on the ground here.

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There's collision on the box.

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There's going to be collision on the wall as well.

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And when we get there, don't, don't, don't at this point right here, he's exited all the collision.

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This collision box is no longer touching our collider that is related to the ground.

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At that point, we're going to say, hey, flip around and then he'll flip and go back the other way.

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And we know how we flip is on our X scale.

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We just hit negative.

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And then when this is no longer colliding, we'll flip again.

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So it's a little bit sneaky.

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We're using on trigger exit.

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So if that's enough for you to go on, if you want to jump in and work on the code for having it flip,

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then pause the video and do so.

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There'll be another challenge, a bit of a shorter challenge when I'm halfway through the code, but

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if you're a bit more of a pro, you're ready for that.

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Then go ahead and do that.

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Hopefully.

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My telescope, my periscope, my reverse periscope.

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Did I call it a telescope before?

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Probably did.

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It's one of those lectures where I'm getting a few things wrong.

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It's a reverse periscope, Rick.

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Now we'll jump back over into our code.

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Stop talking to ourselves.

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We need to say what's going to happen when we do our on trigger trigger exit.

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So similar to on trigger enter but it's void on trigger.

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Exit to DD if we've got one of those.

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There we go.

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It's going to add in a whole bunch of extra stuff I didn't ask for.

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Void on trigger exit to DD.

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Great.

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Now, the first thing I'll do in here is say move.

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Speed equals what?

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Move speed equals minus move speed.

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Which is another way of saying whenever you exit your your reverse periscope exits the thing instead

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of heading in a positive direction, head in a negative direction.

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If you're currently heading in a negative direction, i.e. your x value is is negative, meaning you're

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heading from right to left, then switch it by adding a minus.

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And just a reminder on that, if you have a plus and you combine that with a minus, you get what?

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You get a minus.

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So in other words, adding a minus will actually be subtracting.

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If you subtract a minus, that's the same as adding.

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So that's just a little maths reminder there jump into our maths for games course if you want a reminder

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on all these maths fundamentals as well.

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It's a great cause for a lot of fundamental concepts in there.

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So move speed equals minus, move speed.

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And then we're going to do one more thing in here, which is to flip enemy facing parentheses semicolon.

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This is a method we haven't created just yet, but I'm going to give that to you as a challenge to see

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if you can figure out how to flip the facing direction of the enemy, which is important to make sure

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our reverse periscope is the thing at the front that bumps into the wall.

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So finish the flip and code haha there's a joke for you.

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Finish our code to make the enemy flip directions.

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There's a hint.

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Look at the player movement script for some clues on how to do that.

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So that's all I'll give you for this pause video.

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Take on that challenge.

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So you back in when you done.

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Now.

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What was I talking about?

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Now play a movement code.

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Well, if we scroll around and find where we're flipping the player, it's even called Flip Sprite in

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here.

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You can see we've got this transformed local scale equals new vector to blah blah, blah and we're using

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math sign.

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That's one of our clues.

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I'm just going to copy this line in here.

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This is a good practice.

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I think in coding you want to have a look at what you've coded before or figured out before.

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So I will create our flip enemy facing method, put in our curly braces, and within here I'll paste

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the line that we had before.

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Okay.

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So we do want to transform the local scale and it does need to be a new vector.

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Two We've got our math f sign my rigid body.

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So this is going to say right here, it will say, what direction are you facing?

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Our code is a little bit different to the player code because the player code is reading inputs.

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So we know whether you're pushing a direction on the controller or on the keyboard.

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So we're using that to read what's going on.

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That's why that code is a little bit different here.

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It's simply a case of saying whatever you're doing at the moment, just flip it the other way around

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when this method gets called.

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So in other words, when you use the on trigger exit to DX, so what we're going to do in here is put

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a negative in front of a math sign.

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I need another set of parentheses to wrap around that.

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So basically we're saying whatever your current sign is, in other words, whatever your current scale

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is, just flip that when we tell you to do flipping and that's on the x axis, we don't need to do anything

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on the y axis.

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That's why y axis is one f.

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And just before I save and head back into unity, what have I missed in my method here?

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I'm going to pretend I did this deliberately.

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As a little bit of a micro challenge for you.

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There's something I've missed in here, which means it won't work at all.

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What I've missed is a return type, so avoid flip facing enemies.

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What we need in there and back over into unity.

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There's one last main thing we need to do in here.

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Hopefully you figure this out.

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When you were adding a code and actually getting your character to flip, we need to play around with

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our collision matrix.

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So currently the enemy is on the default layer.

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I'm going to add a new layer which we will call enemies.

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Enemies I think is a good layer, and then click back on Cuba and assign that layer to Cuba and then

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over into edit project settings, physics 2D.

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Hopefully you're starting to get the knack of this now with the layers and with the matrix, the enemies.

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What do we want them to collide with?

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Pretty much just the player, isn't it?

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Not really anything else.

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So I'm going to click all the other things.

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Don't, don't, don't, don't, don't.

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Just to be sure.

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Background.

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No bouncing.

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No.

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Do we want the enemies to bump into each other?

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You may do if you've got a couple of enemies on a thing or you want them to pass through each other.

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So passing through we would turn that off.

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If you want them to bump, then you would turn that on.

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So we'll turn that off for now.

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Oh, and of course, we also need the enemy to collide with the ground or else we don't know when our

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on trigger exit is happening.

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So ground and player, probably not the climbing.

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We don't want it to bump into ladders and we'll see if we've got some success here.

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Just move you a little bit away from the wall so we can get a bit of a run up at it and bounce off it.

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So here we go.

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Bounce, bounce, bounce hits the wall.

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Nothing happens.

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And that's probably, I think because we need this box collider to DH to be a trigger because we were

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using what on trigger exit.

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Now when we click on play hopefully we've got some success here should run up to the wall, bounce into

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the wall and head over in the other direction.

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Excellent.

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And so the play is probably going to mess up the enemy.

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If we run into the enemy, bounce into it.

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We'll set up some functionality in the future where the enemy hurts.

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The player probably causes the player to die.

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But for now, this is the functionality exactly that we want.

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So well done.

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Hopefully you did well in this lecture and I'll see you in an upcoming lecture.