Ben Atherton 2D Side Scrolling Shooter Workflow

2D Side Scrolling Shooter Workflow
Player Sprite
The first task I had to do was to make the sprite for my player to do this I created a new sprite in
game maker named it “Player_spr” to represent that it will be the player sprite and then went into
the sprite editor, this editor contains a variety of tools for creating artwork such as spray can, fill,
shapes, selection, ect however I elected to only use the pencil tool and use different transparencies
of colours in order to make my sprite
My finished sprite looked like the above I took slight inspiration from mario from the mushroom
but I also knew that I didn't want to create an entirely serious game so I figured that a mushroom
flying around in space with a giant mushroom cannon seemed like a good idea as you can see I used
different transparencies of colours in order to add effect to the sprite
The next task was to centre the origin on the sprite this is quite simple all I had to do was click the
button on the origin tab that said centre this now shows the game that the centre of my sprite is the
centre
After this I had to modify the mask of my sprite this is to create the hitbox so that objects know
when they collide with this sprite to do this I had to press the modify mask button shown above and
then I am given the mask properties menu, because of the cannon on my sprite I had to use the
precise hitbox because otherwise projectiles that could otherwise be dodged could hit you in the gap
between the edge of the cannon and the main body of my sprite and all the other shapes would have
a collision happen within this area

Player Object- Movement
My next job was turn the sprite I have just created into an object and make it move around to do this
I selected create object in game maker and named it Player_Obj and then made sure that it was
ticked to be visible and solid then I selected for the sprite of the object to be the sprite that I had just
created and then I added a step event into the events tab and added the code action into it this allows
to me to write code that will effect the object
I then wrote the code shown above which basically checks if the specified button is pressed on the
keyboard and if it does moves the object by the defined amount of pixels in the defined direction for
example y-14 moves it up by 14 pixels the parts of the code that have slashes next to them are
known as hints I used three slashes for the title as game maker recognises this as a title and will then
name the code that so that you can easily find your way around the code the rest only need two
slashes as they are just hints to help me understand what part of the code does what
After I had written this code I created a test room and placed my player object in there and started to
move it around it worked so I knew there was no errors in my code however I could move out of the
room which was a problem so next I needed to work on making the boundaries for my player so
that he can't be moved out of the room

Player Object- Boundaries
To create a boundary for my player I went back into the movement code and added the below to it
This code basically checks where the player is constantly and if it is goes past one of the limits set it
will be teleported instantly to the last possible point it can be at without breaking that boundary in
the case of top this would be y 32 and whatever x the player was already at because the game is
constantly checking this there is no way to actually go past a limit and therefore it creates an
invisible wall effect rather than it being obvious that it's teleporting you I then tested this in my test
and it worked I could no longer leave the room so now my next job was to add a scrolling
background to the room to make the game themeatic and give it a level
Scrolling Background
To create a background I went into the backgrounds section of game maker and selected to create a
new background I then resized this background to 1024x576 as this was the size of my game and
then for the first layer of my background I just made it black as this wouldn't move and would just
be a backdrop for the rest of the background so I just used the fill tool to make it black
As you can see it is not interesting but it was needed for the rest of the background next I created a
new room that I would actually use for my game so I went into settings and made the size of the
room 1024x576 just like the background and then inserted this background into the room by going

onto the backgrounds tab and making it background 0 this puts it at the back of the room so that the
next pieces of my background can go on top of it
As you can see the image selected for it is “Space” which is what I named the black background
next I created the other too backgrounds I wanted which was a planet and stars for the stars I just
drew dots around and for the planet I just used the circle tool the finished products look like the
below

Although on there own all of these backgrounds look weird when they are put together they work
and make something that resembles space quite well the reason why they are all on different layers
is so that they can move around at different speeds and in different directions I can do this by
editing the speeds of the backgrounds in the room
As you can see for my moon it moves from the speeds defined at the bottom this makes my moon
move diagonally down and right my stars just move to the right but at a different speed to the moon
to create differentiate them more and give a semi 3D effect of the different layers moving on there
own together the background looks like the below

Now that my background was done the next job is to allow the player to shoot and add some sound
to the game for when he shoots
Player Object- Shooting
So the next job was to make my player shoot some form of projectile and obviously because my
player is a mushroom with a mushroom cannon the projectile is going to be a mushroom so I went
into the sprite creator and made a mushroom and then realised that on it's own it was not going to
stand out so I added as shield around it to make it stand out so that someone playing the game was
not going to lose there own bullets the finished projectile looks like the below
Next I had to set origin again and set the object mask I just used circle this time as the object is a
circle anyway after this I had to turn this sprite into an object so I went into the object creator and
called it mushroom_obj I then made a create event and called it movement and added the below
code into it

This literately means that when the object is created it will move horizontally across the screen at a
speed of 20 pixels per second I also created another event which was an outside room event and
added the destroy the instance action so that when the projectile went out of the room it would
delete itself in order to prevent lag, next I needed to add the sound for these projectiles are shot so I
went and googled for some cannon sound effects and found an effect that gave the powerful feeling
feeling of a cannon that I was looking for so I downloaded that and then clicked on the add sound
button and added to my game and because it was a quite a small sound file I left it uncompressed
for maximum sound quality I then named this sound cannon and moved on to adding the abillity for
the player to shoot the cannon
To do this I went back into my movement code and added the below code into my game
In other words it checks for if the space key is pressed and if it is then it will create a mushroom at
the centre of the sprite and play the cannon sound that I just added but it won't loop it I then
launched my game and tested if it worked and it did the sound played when I pressed space and it
would spawn a mushroom so my next job was to add enemies to the game that my cannon could be
used to shoot
Enemies- Sprite, Object and System
To add enemies I first had to go and create a sprite for them so I went into the sprite designer and
decided to add floating robots are my enemies I also decided that I wanted to animate them so that
they flashed to do this I had to create multiple sprites that it would change between these sprites
would have very minor changes and would work together to animate the sprite I chose to change the
transparency of the core of the robot to give it a flashing effect I used 5 sprites to do this and the
robot itself looks like the below

As you can see although the differences on each robot are only very minor it cycles through all of
these in order to create a flashing effect next I set the origin and set the object mask I just used a
rectangle for this one as it's fairly rectangular and won't doesn't make any massive gaps that could
get hit that the robot could of dodged and because it will only move sideways it isn't going to be
dodging anything anyway
Next I turned it into an object and began work on making it move I did this by creating a create
event and adding in the below code
This code basically just sets the movement speed of the object to 10 pixels per second and makes
the images animation happen at a quarter of the speed of the room as the room is 30fps this makes
the objects animation happen at 7.5fps in other words it goes through each 7.5 frames every second
the alarm is code that is needed later to let it shoot at the player all it does it makes it activate this
alarm once every 20 frames so it fires just over once per second but because it will only fire one
quite small bullet this is fine
I also added a step event and added some code to destroy the enemies after they leave the room this
code is below
This code basically checks if the object is in a position greater than 0 on the x axis and if it isn't it
will destroy it

Next I needed to create a system that will spawn in these enemies to do this I created a new object
called system and created an alarm the code for this alarm is shown below
This code basically defines y spawn as a random point along the y axis and then creates 3 enemies
at the same point on the x axis right at the end of the screen and then gives them a 64 pixel gap
away from each other it will also trigger it's self at a time between 90 and 120 frames after it was
first set off in other words between 3 and 4 seconds after the first wave is spawned next I added the
system into my room and tested the game and the enemies spawned this means that it works so the
next job is to now make these enemies die when they are shot at by the player
Enemies- Death when shot and particle system
My first job in making the enemies die was to create a particle for them to emit when they die I
decided to draw a 4 leaf clover when they die as this adds in with the plant theme my game has
going with the mushrooms and the overall randomness that the game already has so I once again
went into the sprite editor and drew my 4 leaf clover that I was going to use as a particle and it
looks like the below
Next I created an object that was going to be the particle system for this clover to do this I created a
step event and added this code into it
This code defines chan and part2 as to create a part system and a part type the first line of code sets
the sprite for the particle and says that it wants to be animated stretched and random, the next line
sets the size of the particle making it a max of double the size of the sprite this makes it not increase
in size or wiggle the next line defines the life of the particle this makes it last for a minimum of 3
seconds and maximum of 8 the next line adds random gravity to the particles which makes them fly
around everywhere the alpha1 line sets how transparent the particle is it randomises it between

barely viable 0.1 and quite opaque 0.75, (0 is completely transparent and 1 is opaque) and then the
final line simply says to create the particle system
next I created an alarm with the following code
and a create event to trigger this alarm
This will simply destroy the particle system 5 frames after it has spawned so that the screen is not
spammed with particles and so that it doesn't cause lag
Finally I have to apply this particle system to the enemy so I go onto the enemy object and add a
collide event with the mushroom projectile and then added some code in which says the below
This basically means that when the mushroom collides the enemy it will turn into the particle
system I have just created which deletes it's self after 5 frames therefore killing the enemy next I
needed to make the enemies shoot projectiles for themselves
Enemies- Projectiles
To add enemy projectiles into my game I needed to go back into the sprite creator and created a
projectile for my enemy the red enemy I wanted to just be a basic enemy that was easy to dodge
because I am going to add a variety of enemies into this game with different attacks that do different
amounts of damages are different shapes and move at different speeds so the red projectile looks
like the below
I then set the origin of this projectile and set the object mask I just used a circle again because it is a
fairly circular object next I turned this into an object and added a create event and began to create
the code that will make it shoot at the player the code that I used is shown below

This code basically makes it so that if the player exists the bullets will move towards the point that
the player is at and they will seek the player and head to the point where it is at when it was fired
and it will move at a speed of 15 pixels per second this is ideal as this attack is supposed to be easy
to avoid and do low damage next I added a collision event with the player and made it so that the
projectile is destroyed when it hits the player in order to prevent lag and the player getting caught
on the bullet after he gets hit and I added an outside room event and added a destroy the instance
action in there too so that it won't build up and lag
Next I went onto the enemy object and added alarm 0 and added the code below
This code will make the enemy shoot the lazer and play the sound to shoot the lazer whenever it
shoots it it also triggers it's own alarm every 20 frames making it shoots at just over 1 shot per
second as it did on the alarm used before in the create event which triggers the initial shot
Next I tested that these enemies shot at me and carried on the next job was to create a shield
variable to give the player health
Shield Variable- Defining The Variable And Health Bar
To create a shield variable I went into the system and created new code in the create event this code
is shown below
This code basically creates a new global variable which I have named shield a global variable
means that this variable will now be recognised across my entire game and not just in this one piece
of code and then I defined that shield should = 100 which means that the player will have 100 hit
points
Next I used this variable to create a health bar do this I created a draw event in my system and
added in the below code
This code draws a rectangle at the top left of the screen that is sized depending on the shield
variable it's coloured red and doesn't have an outline
now that the health bar is in the game it's time to start making my enemy do damage to the shield
Shield Variable- Enemies Damaging Player

To make the enemies damage the player I have to go onto my projectile object and create some new
code in the collision event with the player this code is shown below
This code means that whenever the projectile collides with the player the shield variable takes 15
points of damage whenever this projectile hits it this is a fair amount I feel as this projectile is small
and easy enough to dodge and I'll be adding in health pickups and a way to destroy enemy
projectiles later on in the game next I need to add the death of the player when his health reaches 0
Shield Variable- Player Death and Player Death Particle System
For the player to die I need to add a death particle for the player to do this I just created a few
circles of yellow/orange colour that will act as explosion particles the finished sprites look like the
below
So next I need to turn this sprite into a death particle system to do this I created a particle system
called explosion and made a step event and put the below code into it
This is the death particle system this system is pretty much exactly the same as the clover particle
system except I've changed the sprite that is used and changed the words chan and part2 for death
and part 3
next I added an alarm in with the below code
This basically means that when this alarm is triggered it will destroy the particle system and restart
the game as you have lost
and then finally I added a create event which looks like the below

This will basically trigger the alarm shown above and play the player death sound the player death
sound is just a scream that kind of sounds horrible to discourage the player from dieing as they will
have to hear that sound
Now I have to apply this particle system to trigger when the shield variable reaches 0 to do this I
went onto the player object and went onto his step event and added a new piece of code which is
shown below
This code will constantly check what the shield variable is at and when it becomes less than or
equal to 0 it will change the player into the particle system which restarts the game and plays the
death sound so now the next step is to add a score variable in the game to give the player something
to attempt to achieve
Score Variable
The score variable is created in practically the same way that the shield variable was created so I
went into the system and went onto the create event and added the below code
This works exactly how the shield variable works except this time it's set to 0 by default as we want
to be adding to this variable and not taking away from it.
Next I want to add a score counter to my game to do this I need a font so I created a font that is size
12 and uses the segoe UI font and called it font 1
Next I went back into my system and went onto my draw event and added some new code which is
shown below

This code basically draws a white text just below my health bar using the font I just created and
reads out the amount that the points variable is
next I need to make it so that killing an enemy gives score to do this I went onto my enemy object
again and added the below line to my shot by player code in the collision event with the mushroom
This literally just makes it so that whenever an enemy dies to the mushroom the score is increased
by 1.
Now that I have a score system in place the core mechanics of my game are now complete the rest
of this workflow will entail extra tweaks that I have made to attempt to make the game more
interesting the first of these tweaks is enemy variety
Enemy Variety- Blue Enemy
To attempt to make my game more interesting I decided to add more enemy variety to my game
these are essentially just re-skins of the original enemy however they have different attacks and
projectiles the first of these enemies is the blue enemy shown below
The blue enemy fires much larger projectiles than the red enemy that do a lot more damage
however to compensate for this his projectiles are a lot slower and less of the blue enemies spawn in
comparison to reds his projectiles looks like the below
To change how he shoots I edited his shooting code to the below
As you can see this will still seek the player however it moves at a speed of 12 pixels per second so
it is very easy to dodge however it does more damage if you get hit by it as shown in the code
below

So if you get hit by the blue projectile you get hit for a quarter of your health, I also slowed down
his fire rate to one shot every second as seen in the code below
Because alarm[0] = 30 this means that he will shoot once every 30 frames and because the game
runs at 30fps that means he will shoot once every second compared to the once every 20 frames that
the red enemy fires at
Finally I have to add him into the spawning I did this by adding the below code
By putting him at x 1200 he will spawn on the backline of the reds and therefore be slightly
protected as there's only one of him compared to three reds and if he hits you he does a lot more
damage so this formation makes more scene than having him on the front line when he fires slowly
compared to the reds
Enemy Variety- Yellow
My third enemy the yellow enemy looks like the below
I decided that the projectile for this enemy should resemble a shotgun spread and force the enemy to
dodge as it would be quite a long projectile so I created the below projectile
To dodge this projectile you have to dodge all three of the shots this should work in order to keep
the player mobile rather than just sitting in one place and dodging the easy to dodge projectiles the
shooting mechanics for this are exactly the same as the red projectile so it fires fairly quickly and

does 15 damage however only 2 of these spawn in comparison to the 3 red enemies that spawn as
shown in the spawn code below
The yellows make up the rest of the back line with the blue and now all that is needed is one final
enemy to make a line behind the blues and yellows
Enemy Variety- Green
The final enemy that I added into my game is the green enemy and it looks like the below
The projectile for the green enemy is a re-skin of the red projectile however how he fires it will be
completely different the re-skin is shown below
The green projectile will fire very quickly but also very randomly and do little damage the code for
the firing is shown below
This code will literately just send the projectiles to a random point on the map so there's no
guarantee that it will even hit the player the damage of the green projectile is shown below

as you can see it only deals 5 damage but as these projectiles move at 30 pixels per second they are
very difficult to dodge and therefore it is quite balanced to have them shot randomly and do little
damage
Finally I added the greens into the spawning system as shown below
As you can see above the greens spawn on the very back line however there is three of them all
shooting lots of very fast moving bullets in random directions they have the potential to do a lot of
damage or be completely useless which is what makes them interesting enemies the next tweak that
I added to my game was a scaling difficulty system
Scaling Difficulty
For the first minuet of the game the spawn alarm in play is the one shown above that spawns all of
the enemies in a 3 line formation however I decided that for every minuet the game goes on I want
this to be added again so I copied and pasted this onto multiple alarms shown in the below
screenshot (except for one alarm which is used for something different that I will cover later on)
Each one of these alarms have exactly the same sapwn code except from instead of repeating alarm
0 they repeat whatever alarm they are and to trigger all these alarms I use this create event code
shown below

This works by trigger a new alarm every 1800 frames (1 minuet) until all alarms are in play and all
these alarms will repeat themselves so every minuet you survive even more enemies are added to
the game making it even more difficult to survive up until 10 minuets where the game is so near
impossible you will have to be very skilled to survive for long at that difficulty to test if this worked
I changed my shield variable to 99999999999 and left my pc for 10 minuets and when I came back
the screen was spawning lots of enemies at once I then knew that it worked and changed my shield
variable back to 100 however now that the game is this difficult I needed to add ways to balance the
game out so that it was doable and not impossible the first of these was a health pickup
Health Pickup
To create my health pickup I first went into the sprite editor and created the sprite shown below that
I was going to use
Next I created this into an object and gave it the same movement code as an enemy would have
which is shown below
This just makes it move left across the screen at 10 pixels per second next I added a step event to
destroy it if it left the room which looks like the below
And then finally I added a collision event with the player which had the below code on it

As you can see with this code when the player touches the health pickup he gets healed for 50hp I
found this to be the best amount in play testing as when you get higher in the waves 100hp is not
enough and this allows you to stack your health quite high early game to survive the later waves as
these health pickups allow you to overheal
then finally I added a destroy instance action for the heal when it collides with the player so that
people can't just sit on it and get unlimited health
the next thing that I wanted to do to make the game easier with skill was to add a second projectile
that would destroy projectiles
Anti Projectile Missile
To create my anti projectile missile I first made a sprite for it which looks like the below
I then set the origin on this missile and used a pixel perfect object mask on it as it had some large
gaps that other shapes would not ignore next I turned it into an object first I added a create event for
it with the code shown below
This code makes the missile move to the right at a speed of 20 pixels per second when it is fired
next I added a collision instance with all the enemy projectiles that I've added into the game and
added an instance destroy other action for each of them as shown below
And I added a destroy instance self too so that now when the missile and a projectile collide they
will destroy each other this adds a more tactical way of playing the game as you can defend yourself
with the missiles however you have to lower your own firerate to do so and the missiles will not
damage enemies
finally I added the ability for the player to shoot these missiles by adding the below code into the
movement code on the player object

In other words now when control is pressed a missile will be fired now the core mechanics for my
game is complete so I decided that next I should add a main menu with controls and toggle-able
co_op functionality
Menu and Co_OP
To create my menu and have room for my co_op game I created the below rooms
The start menu is the main hub screen which gets you to the controls or the solo/coop menu the solo
game room is the game in solo the coop game room is the game in coop the solo/coop menu is
where you chose to play in solo and coop and the controls menu tells you the controls my first job
was to make these menus navigate-able to do so I used the text tool in the sprite editor to create a
bunch of buttons to get you around the menus and then created these into objects and used the
mouse left click event to send the player to the relevant rooms example shown below
I did this for the play button, back button, controls, button, solo button and coop button and then
after that I created text to show the controls and turned them into objects that didn't do anything
when clicked an example of this is shown below
As you can see this object does nothing other than use a sprite because when this is all put together
in the controls room it looks like the below

As you can see it all fits together quite well and explains the controls and the back button will take
you back to the main menu I also decided around this point that my game should be called shroom
trip as it plays on the idea of a mushroom going a trip or getting high off magic mushrooms so you
would be a floating mushroom shooting floating robots in space it adds to the random and weird
aspect of the game that I've been going for and I thought it was quite a funny name so I kept it
Finally I added co op to do this I copyed and pasted the player object and rebound all the controls to
what is shown in the controls menu above by changing the keys that were bound originally to the
keys I wanted it to use now and then copy and pasting any collision events with player 1 to player 2
and then adding player 2 into the co op game room so now when you click co op the game can be
played with two people after that my game was pretty much finished there was just one thing that
needed to be added...
Music
After searching the internet for a while I finally found some music worth putting in my game so I
added to the sounds as a compressed file and then I created a system like object and put it in every
room with the play sound action put into a create event so as soon as the system is created it plays
the music and then I also added a stop all sounds action to all of the buttons and the player death
particle system to stop it from endlessly looping the music throughout the game
And with that done my game was finished it has full sound effects scaling difficulty a variety of
enemies and projectiles that the player can shoot and a working menu system.

Ben Atherton 2D Side Scrolling Shooter Workflow

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