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Seaweed Assault

An Atari 2600 game by Duane Alan Hahn (Random Terrain).

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Page Table of Contents

Buy Seaweed Assault

Note: Although Seaweed Assault is sold in the AtariAge store, the ROM is made available to play for people who can't afford to buy SwA. Seaweed Assault is not in the public domain. You have permission to use this game with emulators or on a real Atari using a Harmony cartridge or similar device (it will not work with a modded Flashback 2). Please DO NOT include any version of this program in collections or on web sites and please don't put it on cartridge with or without the intention of selling it (don't be a hoser).


This game had a limited edition release on cartridge and it's now sold in the AtariAge store. If you can afford it, please buy it. I also have a tip jar page.




Play Seaweed Assault



Thanks to Paulo Peccin's emulator at, you can play Seaweed Assault right here online for free.

Online Game Controls

Left click inside of the emulator screen with your mouse.


Press the space bar or F12 to start the game.


Move using the arrow keys.


Pause with F2 and continue by pressing the space bar.


Note: The Javatari emulator above now has Joystick support.






Seaweed Assault Online Manual

Buy Seaweed Assault

Online manual last updated on: 2015y_08m_24d_1340t


What kind of game is Seaweed Assault?

It has been said that Seaweed Assault is like a cross between Centipede and Yars' Revenge.



Related links:

Seaweed Assault Review at RGCD

Seaweed Assault Review at 8-bit Central

Seaweed Assault Is Finally Finished

Download Seaweed Assault ROM Here

The Limited Edition Seaweed Assault Cartridge was Sold Here

Seaweed Assault Is Now Sold in the AtariAge Store







Your name is Captain Nalad Modnar and you are part of an advanced underwater civilization. It's your duty to patrol your section of the ocean in a semi-organic submarine called the Manatee. Highly aggressive seaweed surrounds you and it keeps trying to replicate faster than you can shoot. Use your torpedoes to blast any bits of seaweed that appear before they clog up your sector and spread to others, making it nearly impossible for anyone to travel. Don't let the seaweed strangle your civilization to extinction.








Attract Mode and the Title Screen

Attract mode displays the title screen for 10 seconds, then switches to a computer-controlled gameplay demo. This attract mode sequence repeats until you are ready to play. If you move the joystick up, down, left, or right while the title screen is displayed, a sound effect will be played so you can adjust the volume on your TV before the game starts.


Tip: If you use the Stella emulator, Alt + P will make the title screen look better.




Starting and Restarting the Game

The game can be started with the reset switch or by pressing and releasing the fire button on the left controller. Press the reset switch while playing if you want to restart the game and return to the title screen.



Left-Handed (photo by Albert from AtariAge and cleaned up by Duane Alan Hahn)
Right-Handed (photo by Albert from AtariAge and cleaned up by Duane Alan Hahn)

Right-Handed or Left-Handed Play

Most Atari 2600 games only allow right-handed play. Seaweed Assault offers another option for left-handed players. Any time during the attract mode sequence, press the select switch to toggle between right-handed (RH) and left-handed (LH) play. For right-handed play, the fire button of a classic-style joystick should be in the top left corner. For left-handed play, a classic-style joystick should be rotated clockwise so the fire button is in the top right corner. When you toggle between them, RH or LH will be displayed. If you accidentally start the game with the incorrect controller configuration, press the reset switch to return to the title screen and select the correct configuration.





To pause the game on an Atari 2600, flip the COLOR/BW switch. To pause on an Atari 7800, press the pause button. You can also pause the game by pressing the fire button on the right controller. To resume play, press and release the fire button on the left controller. Remember, you must release the fire button to resume firing torpedoes (this feature keeps you from shooting something you may not want to shoot).


The pause feature displays random colors to help protect your television. Only the score and Manatee are shown during pause to prevent cheating. The Mantee is displayed during pause so you'll know your exact position when you resume play.




Manatee Movement

The Manatee is capable of full 8 directional movement (up, down, left, right, and diagonally). The fire button can either be pressed and released for each torpedo or held down for auto-fire. There is no rapid fire because a string of torpedoes would have an explosive chain reaction and destroy the Manatee.







Seaweed Assault

The Manatee is a semi-organic submarine that moves by using two flippers in the back that flap a little, but mostly undulate in a similar way to how certain types of stingrays and skates undulate the edges of their pectoral fins. Below are two example videos.


The Manatee has thick, gray, shark-like skin that is self-repairing. Whenever the Manatee is damaged, it will use a unit of health energy to automatically repair itself. The Manatee needs at least one unit of health energy to stay healthy, so when you are down to four units, the Health Energy Indicator will turn yellow and when you are down to one unit, it will turn red, alerting you that any more damage will end your mission. But don't worry, the Manatee starts out with 16 units of health energy and more units can be earned and uncovered. (The Health Energy Indicator is located on the bottom of your view screen within the Manatee's Communications Panel.)


The Manatee uses the Communications Panel to inform you of necessary information. The Manatee can sense the seaweed getting more aggressive. For every 20 pieces of seaweed you shoot, the Manatee will let you know that the seaweed is getting more aggressive by making the shade of the Communications Panel a darker green. When you shoot 100 pieces of seaweed, the darkest shade will change back to its lightest shade to let you know that the rate of reproduction has increased. The Manatee sends this information to Central Command and when 100 pieces have been shot, they reward you with a homing health canister to prepare you for the new reproduction rate. The Manatee can detect that the canister is near and will let you know by making the Communications Panel blink blue. The Communications Panel also displays your score and shows your high score during auto-play.


The Manatee's skin has bioluminescence for damage and for absorbing energy. When damaged, the skin will blink red and when absorbing energy, the skin will blink blue.








Wrothopods are a protected species of cephalopod that travel deep to feed on parasites that attach to mature seaweed (they have a symbiotic relationship). Like many sea creatures, wrothopods are bioluminescent (they can emit various shades of colorful light). Wrothopods are a little cranky and have a hammerhead similar to a hammerhead shark, so stay out of their way. Just like with the seaweed, if the Manatee touches a Wrothopod, the Manatee will have to use a unit of health energy to repair itself.


To discourage poaching, no torpedo can harm a Wrothopod. The damage will be transferred back to the vessel of origin. In other words, if you shoot a Wrothopod, you'll hurt the Manatee instead. Although torpedoes cannot harm Wrothopods, the experience isn't pleasant, so a Wrothopod will go from cranky to furious if shot. When one is furious its skin will change to a reddish color and it will dart at you faster.







The Manatee will be damaged if you bump into the mature seaweed that has closed in on you or the seaweed offspring that keep popping up. The offspring may look passive, young and stupid, but don't get too close. They are sticky and will try to hold onto the Manatee until every bit of health energy has been used up. Keep your distance and use your torpedoes to clear a path.


Warning: Every time you shoot 100 bits of seaweed, the mature seaweed will start to panic a little and increase the rate of reproduction. The background color behind the score will get a little darker each time you shoot 20 bits of seaweed so you'll know how close you're getting to 100. Once you shoot the 100th piece of seaweed, the score bar will flash and you'll start on the next 100.









Homing Health Canisters

Health Canisters

Shoot 100 bits of seaweed and a homing health canister will be dropped by your leaders for your hard work. Homing health canisters are supposed to move toward the Manatee, but they are made in a hurry, so they aren't exactly top-quality. That means homing health canisters will often be defective and drop straight down.


Defective or not, homing health canisters will weaken the deeper they fall. Get to them as quickly as possible. A health canister glows blue at full strength and is worth 3 units of health energy and 50 points. When it turns yellow, it's worth 2 units of health energy and 25 points. When a health canister is about to give out, it turns red and is worth one unit of health energy and 10 points. If your Health Energy Indicator is full, any extra health energy will be converted to points.



Reminder: Remember, every time you shoot 100 bits of seaweed, the mature seaweed will start to panic a little and increase the rate of reproduction. The background color behind the score will get a little darker each time you shoot 20 bits of seaweed so you'll know how close you're getting to 100. Once you shoot the 100th piece of seaweed, the score bar will flash and you'll start on the next 100.






Corroded Homing Health Canisters

Health Canisters

You'll never know where or when, but sometimes a long lost Corroded Homing Health Canister will be trapped behind a bit of seaweed. When you shoot that bit of seaweed, the Corroded Homing Health Canister will be released and it will take around 3 seconds for its sensors to activate. If you can salvage it in time, you'll get one unit of health energy and 10 points.


Since every Corroded Homing Health Canister has damaged circuits, if you don't salvage it before the sensors have activated, it will use its last bit of energy to home in on the Manatee and try to ram it, causing damage that will take one health unit to repair.


The bad news is that you can't shoot it or outrun it. The good news is that it can get caught up and lost in the bits of seaweed again, so if a Corroded Homing Health Canister comes after you, try to get some seaweed between it and you.


Corroded Homing Health Canisters make a sound while trying to activate which confuses mature seaweed tentacles and makes it harder for them to sniff out your 'scent,' so they will hesitate before going after you.






1,000 Point Energy Burst

Any time you earn 1,000 points, you are showing your worth to your leaders, so they will use their most expensive piece of technology and send down an energy burst that will instantly fill your health energy (the seaweed will temporarily turn blue as the energy surges down through your sector). And it's not just a one-time bonus. Your leaders will send down an energy burst at 2,000, 3,000, 4,000, 5,000 and so on.






About This Game and Special Thanks

Seaweed Assault was made with batari Basic (a BASIC-like language created by Fred "batari" Quimby that helps the average person make Atari 2600 games). This game started out as an example program and was made by Duane Alan Hahn (Random Terrain) using hints, tips, code snippets, and more from AtariAge members such as batari, SeaGtGruff, RevEng, Robert M, Atarius Maximus, jrok, Nukey Shay, supercat, GroovyBee, and bogax. Thanks also goes to those who posted in the Seaweed Assault thread in the batari Basic forum at AtariAge.


This game would not exist without batari Basic by Fred "batari" Quimby and Visual batari Basic by jwierer. Visual batari Basic's various editors and useful features make the whole process faster, easier, and more fun.


Sound effects were created by hunting down sounds with Tone Toy 2008 and shaping/altering those sounds using VbB's Music and Sound Editor.


Name of semi-organic submarine (the Manatee) suggested by Christophero Sly.


Wrothopod name influenced by something Mili said in the AtariAge chat room:

--- Mili: but its wroth it to be on there

--- Random Terrain: The Wroth of Mili!

--- Mili: Fear my Wroth RT


Schizophretard suggested many ideas to improve the game, suggested improvements to the manual and provided additional text to make things clearer, and also did a lot of testing on real hardware.


Zach suggested an improvement to make the left-handed feature easier to understand.


Game box, cartridge, and manual art created by Brian Ostrowski. He also created the PDF manual for printing.


CPUWIZ did the limited edition Seaweed Assault cartridges and Albert eventually put the game in the AtariAge store (with box and without box).


Thanks also goes to L-Tyrosine. It gives me a little more energy and helps me to focus and get things done. It's not a cure for my problems, but as you can see, this game is finally finished. Not something that would have happened before taking L-Tyrosine. There's hope that the other games I started years ago will get finished now.






Play the Game

You can download the latest .bin file at AtariAge to use with an emulator or Harmony cartridge:


Thanks to Paulo Peccin's emulator at, you can play Seaweed Assault on this page. You can also buy your own Atari 2600 Seaweed Assault cartridge from the AtariAge Store.




Easter Egg

Can you find the Easter egg? If you find it, please let me know about it by posting in the Seaweed Assault thread at AtariAge. But please don't say how you found it or what you saw on the screen. Thanks.



Thanks to Paulo Peccin's emulator at, starting on on May 24, 2012 it became possible to play Seaweed Assault online for free.


Download the ROM


Seaweed Assault Reviews

Harmony Cartridge

Other Programs

Tone Toy 2008

Play with Atari 2600 sound effects or use it to find new sounds for your games.


Double-click Draw: RT Version 01

This is my normal version of a program by Fort Apocalypse.


Double-click Draw: RT Version 02

Thanks to batari, this is my version of a program by Fort Apocalypse that lets you change the color of each row.


Music Starter using sdata

The 256-byte limitation is removed when using sdata. Be sure to try the Music and Sound Editor (it outputs similar code using data or sdata).


Tweaked Ballblazer Tune

My edited version of thegoldenband's tune.

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In Case You Didn't Know


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Check out these videos:

Best of Sped Up and Edited Tennessee House of Representatives Health Subcommittee Hearing Room 2 (March 1, 2022)

Full Video of Tennessee House of Representatives Health Subcommittee Hearing Room 2 (The Doctors Start Talking at 33:28)



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Litterbugs = Bad

Never litter. Toss it in the trash or take it home. Do not throw it on the ground. Also remember that good people clean up after themselves at home, out in public, at a campsite and so on. Leave it better than you found it.



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Watch these two YouTube videos for more information:

CO2 is Greening The Earth

The Climate Agenda


View this page and any external web sites at your own risk. I am not responsible for any possible spiritual, emotional, physical, financial or any other damage to you, your friends, family, ancestors, or descendants in the past, present, or future, living or dead, in this dimension or any other.


Play this game at your own risk. If you swallow your tongue or develop anal leakage, I am not responsible. Do not play this game while driving or juggling flaming bowling balls.


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