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- Hi.

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Welcome to Structuring
the Thomas Was Late Code.

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In the previous video,

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we looked at Thomas Was Late Game.

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In this video, we're going to improve

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the manageability of
the code in this project

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with the help of Engine class.

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One of the problems that
has been quite pronounced

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in both projects so far

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is how long and unwieldy the code gets.

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OOP allows us to break our projects up

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into logical and manageable
chunks called classes.

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We will make a big improvement

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to the manageability of
the code in this project

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with the introduction of an engine class.

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Among other functions, the engine class

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will have three private functions.

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They are input, update and draw.

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This should sound very familiar.

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Each of these functions

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will hold a chunk of the code

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that was previously all
in the main function.

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Each of these functions will
be in a code file of its own.

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Input.cpp, Update.cpp and
Draw.cpp respectively.

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There will also be one public
function in the Engine class,

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which can be called with
an instance of Engine.

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This function is run
and will be responsible

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for calling Input, Update and Draw

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once for each frame of the game.

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Furthermore, because we have abstracted

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the major parts of the game engine

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to the engine class,

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we can also move many of
the variables from Main

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and make them members of Engine.

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All we need to do to get
our game engine fired up

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is create an instance of Engine

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and call its Run function.

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Here's a sneak preview of the
super-simple Main function.

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Don't add this code just yet.

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To make our code even more
manageable and readable,

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we will also abstract
responsibility for big tasks,

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such as loading a level
and collision detection

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to separate functions
in separate code files.

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These two functions are
loadLevel and detectCollisions.

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We will also code other functions

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to handle some of the new features

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of the Thomas Was Late project.

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We will cover them in detail
as and when they occur.

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To further take advantage of OOP,

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we will delegate responsibility
for particular areas

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of the game entirely to new classes.

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You probably remember that
the sound and HUD code

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was quite lengthy in previous projects.

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We will build a sound
manager and HUD class

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to handle these aspects
in a cleaner manner.

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Exactly how they work
will be explored in depth

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when we implement them.

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The game levels themselves
are much more in-depth

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than previous games,

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so we'll also code a level manager class.

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As you would expect,
the playable characters

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will be made with classes as well.

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For this project, however,

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we will learn some more C++ and implement

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a playable character class

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with all the common
functionality of Thomas and Bob

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and then Thomas and Bob classes,

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which will inherit this
common functionality

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as well as implement
their own unique functions

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and abilities.

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This perhaps unsurprisingly
is called inheritance.

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I will go into more
detail about inheritance

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in the next section.

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We will also implement a
number of other classes

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to perform specific responsibilities.

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For example, we'll make
some neat explosions

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using particle systems.

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You might also be able
to guess that to do this,

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we will code a Particle class
and a ParticleSystem class.

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All these classes will have instances

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that are members of the Engine class.

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Doing things this way

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will make all the features
of the game accessible

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from the game engine, but
encapsulate the details

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into appropriate classes.

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The last thing to
mention before we move on

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to see the actual code that
will make the Engine class

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is that we will reuse without
any changes whatsoever

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the texture holder
class, which we discussed

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and coded for the Zombie Arena game.

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Cool!

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In this video, we learned

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structuring the Thomas Was Late code.

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Next up, we'll see
building the game engine.