Sonic 1 Flash Flood

By TheInvisibleSun

It's cloudy with a chance of monsoon in South Island today...

Sonic 1 Flash Flood is a ROM hack of Sonic the Hedghog that features new palette, audio, zone layout and special stage modifications, in addition to new gameplay mechanics. Flood waters rise and recede at random all over the island, significantly changing how the island is navigated. Can you make it through?


  • Level Design - In addition to the rain effect and water palettes, level layouts are tweaked to account for water physics.
    • Marble Zone has altered lava physics, and Acts 2 and 3 have new shortcuts.
    • Being entirely underground, Labyrinth Zone has been affected a bit...differently by the change in weather.
  • Goggles Monitors - These take the place of air bubbles, and are thus unlimited. Use as many as you need!
  • Badnik Behavior - The rain and flooding is even affecting Eggman's robots and hazards, causing them to malfunction! Some are even enhanced by the chaotic weather. Strangely, most fire-related hazards (such as flamethrowers and fireballs) remain unaffected, defying all logic.
  • Special Stages - New special stage gameplay style, with art and music changes. Get Yellow Rings!
  • Water Physics - Some general quality of life improvements to the water physics, and bug fixes are included here (with a few exceptions, for gameplay reasons).
  • Level Select - Available upon pressing start, no code required. Feel free to check out any zone or special stage at your leisure.

Known Bugs:

  • Minor graphical bug in the special stage background, and on the results screen.
  • In the Special Stages, blocks at the edge of the screen being loaded in flicker, due to the amount of objects.
  • Level art mapping glitches crop up on rare occasion.
  • Labyrinth and Scrap Brain's palette cycles are bit buggy at the moment.
  • There are a couple of lingering walk-jump bugs here and there

Planned Features

  • Improved object optimization
  • Importing Sonic 2-3's child sprite system
  • Underwater sound/music mode
  • Even more environmental effects.
  • More significant changes to bosses, Final Boss, etc.

Thanks for Playing!


Special Thanks:

Nineko - Testing

Gardeguey - The PalLoad_Loop subroutine

MarkeyJester - Deformation, and HUD assistance

RetroKoH - Sonic Triad

snkenjoi - Flex2

MainMemory - SonLVL Program Suite

King Meteor/Monster Iestyn - TTGF midi

Oerg - Instrument pack

ValleyBell - mid2smps/SMPSPlay


The Geek Critique



File Type: 7z

File Size: 422.02 KB

TheInvisibleSun @ 2021-10-02 13:15:18

Also, a very special thanks to Vladikcomper, who helped fix a critical bug.

dilworks @ 2021-10-11 17:02:05

Reverse flooded LZ feels so wrong~~~

Jdpense @ 2021-10-12 19:59:50

I really dig the special stages! Although, I wish there were a way to speed up Sonic in the stage such as via pressing or holding a button for instance.

TheInvisibleSun @ 2021-10-12 21:30:05

Noted; Great suggesstion!

KosmoF @ 2021-10-13 02:32:19

I really like this hack, but those Special Stages are hard as hell; after hours of raging at the game yesterday I eventually got all the emeralds, but Sonic descending so fast (and that's playing with PAL settings) was so infuriating that I rage quit the game.

Last modified by KosmoF @ 2021-10-13 03:05:43

TheInvisibleSun @ 2021-10-17 11:23:59

Thanks for the feedback! Ironically, I made the special stages much easier than they were in previous iterations. It's also strange to see that others want a speed up function, as stated above; maybe this calls for difficulty settings? Either way, thanks for playing!

goodegames @ 2021-10-16 18:47:36

A very fun hack. I think it would be cool to see an option in the future to have the water stay permanently as a challenge mode. The hack really keeps you on your toes so keep up the great work!

TheInvisibleSun @ 2021-10-17 11:25:04

Thanks for the suggestion! I'll consider it, especially considering this isn't the first time I've heard this mentioned.