EUCLIOD - A Homebrew Bullet Hell for the 3DS

Before I say anything else, I'd like to mention that this project was developed and bugtested on, and for the New 3DS system.

Rinnegatamante has helped me optimize the game, and the game runs almost flawlessly on N3DS (at present) and although I am aiming to keep the game smooth as possible for the O3DS, don't expect any miracles. (Though I have been informed that the game currently runs at 60 FPS on the O3DS)


This has been a quick project I've undertaken to have a little test of the boundaries of the N3DS's processing power vs the O3DS. (as seen through the eyes of Rinnegatamante's LPP)

It's also (hopefully) going to be the first game I actually complete in the last 7 years of making random games that are too ambitious for me to finish.




Video by TCPixel (Thanks a tonne man)

I've only got three levels in at the moment (my level design skills suck) but the levels are stored in plain text file so it should be easy enough to create more. 6 enemies , 3 bosses with multiple phases, and 5 different weapons. It's a bullet hell game: so you get one life, and a tiny hitbox.

The difficulty system isn't tested, I did most of the bugtesting on the highest difficulty (for the sake of keeping an eye on lag levels), so I don't know if the easier ones are laughably easy or broken.

A -
Select (menu only... I'm currently sick of holding down A when playing Mario Kart, and mashing it for Fantasy Life)
B - Back (only works on ship select screen)
Y - Fire Primary
R - Focus Mode (halve movement speed, and uses an alternate weapon)
Start - Return to Menu
Select - Take Screenshot
On the menu, use left and right to increase/decrease difficulty, and change the level (hold Y while changing level to speed-cycle)
You can remap the Fire and Focus controls to A, B, X, Y, L, R, ZL, or ZR in the options menu if you don't like the default.
The game is currently D-Pad only, but adding in circle pad controls wouldn't be a stretch. :)

If anyone gives a crap about level making:
The game will load from any level named correctly. levelx.dat should be the filename where x is the number with no spacers. The game will state invalid if the file does not exist or if the file does not have "v001" on the first line.
The game will likely crash if you have both these but the syntax in the file is incorrect.

v001 //add this to the start of every level you make, it won't start without it

Every line has to be exactly 20 characters long, in this exact format (my text-parser programming skills suck)
The first 6-digit number is the frame the enemy spawns, if you're not lagging this should be 60 per second.

The second cell is the enemy that's spawning.
  • "en01" (Fighter) is the enemy that targets you with bullets
  • "en02" (Bomber) is the enemy that sits still and shoots slow bullets directly downwards
  • "en03" (Strafer) is the sliding enemy that lays down a curtain
  • "en04" (Helix) is the enemy that shoots a helix of bullets and diagonal shots alternatively
  • "en05" (Kamikaze) is a slow moving enemy that proceeds down the screen and then detonates into a ring of bullets if not destroyed
  • "en06" (Asteroid) is a large object that soaks up player shots. Graphic and direction is deterministic based on the frame it was spawned in
  • "en07" (Odin) individual mob. Untested.
  • "bo01", "bo02" and "bo03" are the three current bosses, and spawn after a warning is flashed on screen. Note that two bosses cannot be spawned within a short period of eachother. (and probably not even on the same level, this is largely untested)
The third cell is what side of the screen the enemy will enter. Top, Left, or Right. Note that I haven't tested how en03 works when entering from the Top, and I haven't tested how bo01 works when entering from Left or Right. The whole enemy spawning system is really bare-bones at the moment.

The final cell is the coordinate the enemy spawns at. For Top spawning enemies, this number is the X-coordinate they spawn at, (between 0-400 for left-right) and for Left and Right spawning enemies, this is the Y coordinate. (0-240 for top-bottom)

Okay, bored now?

[3DSX] Release 6.1
  • Re-added a null file that had been accidentally removed, to fix the red bar loading issue
[CIA] Release 7
  • Bullets now clear on stage clear
  • Control configuration and theme does not currently save as the config file is in a read-only location
  • Sounds have been disabled as a crippling bug in CIA form causes sounds to loop and memory leak, I have not identified how to solve this problem
  • As the CIA is a compiled installation, there is not currently a way to use custom levels with the CIA version
[3DSX] Release 6
  • Added sound effects
  • Color scheme is now changeable from options menu. (includes high contrast black and white mode)
[3DSX] Release 5
  • Added new enemy, "Kamikaze"
  • Added new enemy, "Asteroid"
  • Enemies now will kill you on contact
  • Added Level 3, featuring the two new enemies and a new boss, "Odin's Fleet".
  • Bosses now clear bullets before starting the next phase
  • Corrected a calculation error with the scoring (Difficulty was linearly increasing score instead of multiplicatively)
  • Made some dramatic hitbox corrections for enemy ships
  • Increased Level 1 and 2 boss health by 140% to counter the hitbox change.
  • Grazing has temporarily been removed as a new, faster, and pixel-accurate player hit detection system has now been implemented. Grazing may be added back in a later update
  • Fixed a bug that was causing homebrew launched after EUCLIOD to have messed up graphics
  • FPS counter (hopefully should remain at 60 at all times)
  • Boss health bar
  • Debug mode (hold X before loading screen displays) includes "slideshow" recording which replaces screenshots, displays a couple debug values on the bottom screen, and ups Level 1's boss's final attack to one hundred and eleven for testing lag
  • Fixed a bug that was causing multiple level's enemies to load if you chose a level then backed out of the ship select screen before choosing another level
  • Credits added
  • Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience
[3DSX] Release 4
  • Added variation to Level 2 boss's tidal wave attack to eliminate safespots
  • Added two ship types: "Tiger" and "Cicada"
  • Ship selection screen
  • The original ship, "Hawk", received a 25% movement speed reduction
  • Weapons are no longer freely scrollable. Each ship has a Primary weapon and a Focus weapon, which automatically engages when you enter focus mode. You can press Y on the ship selection screen to disable the focus weapon, which causes the Primary weapon to be used for both modes.
  • Corrected a bug that was preventing enemies from despawning and thus the level from being cleared
  • Increased graze range by 30% and doubled point reward for grazing
  • Taking screenshots now works
[3DSX] Release 3
  • Added level 2, including a new enemy (Helix "en04") and a new boss "bo02"
  • 3 New bullet types used by these two enemies: "Sway", "Diagonal", and "Moving Orbitals"
  • Corrected bug that was causing previously loaded level's enemies to spawn (only matters if anyone actually made any levels
  • Buffed seeker shot damage and tracking
  • Nerfed missile's hitbox
  • Exit button works now (big whoop)
  • Tweaked strafers so that they're not so insane on lower difficulties
  • Basic enemy shots now travel slower but have larger hitboxes
  • Basic score counter implemented. Kills and graze count towards score
  • The game will now return to menu once the level is cleared
  • Shortened enemy despawn time to reduce lag
  • Buffed boss health
  • Added "Stage Clear" text. Game will return to menu shortly afterwards

[3DSX] Release 2
  • Substantial optimization regarding boss bullet spawns, seeker rounds, all player shots in general, and moving enemies
  • N3DS mode automatically activates for N3DS systems. O3DS mode can still be forced by holding Y upon launch.
  • Combined, these two changes create a DRAMATIC performance boost for the game, so you can look forward to a lot more bullets in the future
  • The game now returns to menu several seconds after a death. You can still reset early by pressing Start.
  • Custom keybinds menu added. Keybind settings are persistent.
  • Enemies now despawn after 1000 ticks

3DSX: Just extract the archive straight to your SD card and launch via Homebrew Launcher. The unsuffixed zip files are the 3DSX versions.

CIA: Install the CIA using FBI. The zip file with "_CIA" on the end is the CIA version

Despite the CIA version having a more recent release, the 3DSX version is still superior. So if you don't mind going 3DSX over CIA, I'd recommend it.

Mod edit. Download links

Credit to Rinnegatamante for developing Lua Player Plus, the application that allows me to program in notepad and not need to know a single other thing about computers or compilers.


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Last edited by HexZyle,


Well-Known Member
Nov 24, 2014
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Pretty Petty Pedant
Sep 12, 2015
I can give it a try, i'm pretty interested on seeing this running good on my O3DS with 4.5 fw <.<
If you can help optimize it, that would be great.
I actually have no clue how to compile the game into a package.

It seems that the player's bullets in the game are the laggiest parts as they have to check their collision box with every enemy on screen (recalling data from arrays), every bullet is roughly as resource-intensive as 10-15 enemy bullets, so no big spreadshot crazy weapons yet. (the game did not like having weapon 1 shooting two separate objects)
Then again, my most recent bug in the game is getting the game to detect when all enemies are dead and thus the level is complete (which it does so by checking enemylist.size, which should increase each time an enemy is spawned, and decrease each time one dies) so perhaps that's the source of the problem.
It could be an easy fix, but it's late and I just wanted to upload this before I get to bed because I got work early tomorrow.
Last edited by HexZyle,


Well-Known Member
Jan 12, 2015
United States
It seems that the player's bullets in the game are the laggiest parts as they have to check their collision box with every enemy on screen

Quadtrees. Sort objects into quadrants of quadrants of quadrants (until it hits the max or is bigger than the next cell level) and only check collision with things that could be adjacent. Also, if you have pixel collision, rule out by axis-aligned bounding box first.


Pretty Petty Pedant
Sep 12, 2015
Same here, what firmware (and nh build) are you on? I noticed some old payloads don't have romfs support.
Ah. Emunand 10.7, hax 2.5 I believe.
I thought the index file goes in the same directory as the 3dsx file. Is it not there?

Last edited by HexZyle,


Well-Known Member
Oct 15, 2015
It's really cool (judging from the screenshot, didn't test it yet) i always wanted to program a game like this myself but i lack in any graphical design skill. (Would love to see the source code to imagine the amount of work involved into a game like this)
Last edited by Slashcash,
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