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Thread: Gravity Pig - homebrew platformer for Genesis

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    Comrade as in friend. Master of Shinobi ComradeOj's Avatar
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    Default Gravity Pig - homebrew platformer for Genesis

    After a ton of time and work, I can now declare this game to be "releaseable". Development has taken just over 4 months of mostly 'on' work. I did all the programming, music, design, testing, and art myself, so it took quite a long time to get anything done. The game can still be improved, and has issues that could still be worked out. I might come back and do an improved sequel, depending on how this one is received.

    I played the ROM I'm releasing over and over again, so I hope I didn't accidentally screw something up. The game has so much do it, that it would be easy to forget about something I changed just to test. I've also never written music before this. All the songs in the game are originals, so hopefully they at least sound okay. I particularly like the ending theme.

    First things first.

    Here is the trailer I put together:


    Here is the ROM download link: https://drive.google.com/file/d/0B-u...ew?usp=sharing
    It is Highly recommended that you don't run the game in FUSION or GENS! Those two emulators don't emulate the VDP's sprite collision detection quite right, and it will cause the final boss stage to constantly steal lives from you, even if you don't get it. It works fine in the REGEN emulator, or on real hardware via a flash cart.

    What is Gravity Pig?
    It's a simple platformer game, with (very) light puzzle elements but without jumping. Instead, you must get around by reversing gravity. I have showed it to a few people, and one compared it to VVVVVV. I've never actually played that game, but I watched a video of it and I could see the similarity. Gravity Pig was actually inspired by a flash game called This Is The Only Level. The gravity flip mechanic was used because it was easier to program than jumping.

    There are 3 different themed areas, each with 5 stages. That's not whole lot of levels, especially considering their small size. It was a lot harder to come up with challenging stages than you might imagine. I didn't want to re-hash too many obstacles or ideas, so I was only able to come up with 15.

    How is it played?
    You make your way through the levels to reach the goal post at the end. Along the way, you can collect extra lives, coins, and extra "Gswaps". You can only switch gravity a limited number of times, and a "Gswap" icon lets you do it an additional time. The game is what I call a "semi-scroller". The levels do scroll left and right, but not very far. You will be moving right about as often as you move left.
    The Genesis resolution is 320x224, and the levels are all 512x224. So, the levels can scroll 96 pixels in either direction.

    The story
    There is a simple story but it's only about as deep as the plot of sonic 1. An evil mystic kidnapped all the pigs, and you have to journey to her lair to confront her and free the pigs.

    Development diaries
    One challenge was creating levels out of tiles that could be used for collision. I could draw a static image that looked like a stage, but the game's engine would have no way of working out collision properties. So, I figured out a way of using the same chunk of data for design, art cues, and collision. The level data is basically a chunk of text with each letter corresponding to a different type of block. This chunk of text is loaded into VRAM to display the graphics, and RAM for the engine to probe sections of the stage and determine collision.

    Look familiar? This stage was used in the trailer.


    This is what each letter corresponds to (lowercase for reverse version)
    G = grass
    S = spike
    I = exit
    E = upside down exit
    W = wall
    D = dirt
    L = life power-up
    P = G-swap power-up
    B = bacon
    K = sideways spike
    ! = shadowed tile

    During development, coins used to be bacon. The original plot called for all the pigs being turned into bacon by aliens. The Gravity Pig would collect the bacon to bring to the mystic, so that she could restore them back to being pigs. I started to dislike that plot, so I just made the mystic into the villain instead and cut out the aliens entirely.

    Some fun facts that I couldn't fit in anywhere else:
    Gravity Pig was programmed almost entirely using an American made keyboard.
    Gravity pig uses a 32-bit checksum, but it's not enforced.
    The Mystic Offender graduated from the University of Strathclyde with a major in sorcery and a minor in mathematics.

    Here is a breakdown of the type of instructions used in the game:
    (Not embedding as image, because giant obnoxious pie chart)
    This chart shows how many instructions are either 32, 16, or 8 bits.
    http://i.imgur.com/rLZkrJA.jpg

    This one shows what type of instructions were used:
    http://i.imgur.com/T141w4Q.jpg

    All hail the mighty MOVE instruction!!
    Modded consoles:
    Master System (v7040) with s-video & direct AV out
    Model 1 with 10mhz overclock & halt switches
    Model 1 with 10mhz 68010
    Model 2 VA2.3 with unfiltered Mega Amp, & s-video
    Model 3 VA1 with compatibility fixes & s-video
    32X with s-video
    Visit my web site at www.mode5.net
    Or my collection of homebrew Genesis games, programs, and music on SEGA-16!

  2. #2
    16-bits is all he needs Master of Shinobi matteus's Avatar
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    Haha love it! unfortunately I can't give you any more rep but thank you for your efforts in our growing dev community!


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    Creeping Death-ah! Wildside Expert Metallica Man X's Avatar
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    Pretty sweet! The music sounds kinda like "25 or 6 to 4" by Chicago, which is not a bad thing! lol
    I mostly lurk...don't be alarmed when you see me actually make a post :P

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    I like it, it's tough in the Tundra stages, all that up and down lol. I like the music a lot, Pig's Song is very catchy and drives you to keep trying. Simple story but the main character is easy to empathize with.

    I'm finding the main menu pages a little too twitchy and fast to navigate, you really have to tap way too quickly to move over one page.

    Is there an infinite life option because these kind of games are lots of trial and error? Maybe a level password system so you don't have to play through all the levels you've mastered or barely got through. I'll keep trying but I don't think I'll get to the 15th level with limited lives.

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    Comrade as in friend. Master of Shinobi ComradeOj's Avatar
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    Quote Originally Posted by Metallica Man X View Post
    Pretty sweet! The music sounds kinda like "25 or 6 to 4" by Chicago, which is not a bad thing! lol
    Hey, it kind of does! I never noticed before. The bass part especially.

    Quote Originally Posted by BladeJunker View Post
    I like it, it's tough in the Tundra stages, all that up and down lol. I like the music a lot, Pig's Song is very catchy and drives you to keep trying. Simple story but the main character is easy to empathize with.

    I'm finding the main menu pages a little too twitchy and fast to navigate, you really have to tap way too quickly to move over one page.

    Is there an infinite life option because these kind of games are lots of trial and error? Maybe a level password system so you don't have to play through all the levels you've mastered or barely got through. I'll keep trying but I don't think I'll get to the 15th level with limited lives.
    Are you using a 6 button controller? I've had a tough time getting input to work correctly on those. Specifically waiting for the button to be released. It should work a lot better on a 3 button pad. The sound test will still be a bit twitchy not matter what though .

    I was kind of afraid the difficulty would be too high. The difficulty is very hard to measure, since I designed the stages, and probably played through them about 50 times. Hopefully a decent amount of people that play it can make it to the end. I hope it will be amusing when you get to the villain, and see the short dialogue. If I ever do a sequel, I'll probably get some people to play the stages beforehand.
    Modded consoles:
    Master System (v7040) with s-video & direct AV out
    Model 1 with 10mhz overclock & halt switches
    Model 1 with 10mhz 68010
    Model 2 VA2.3 with unfiltered Mega Amp, & s-video
    Model 3 VA1 with compatibility fixes & s-video
    32X with s-video
    Visit my web site at www.mode5.net
    Or my collection of homebrew Genesis games, programs, and music on SEGA-16!

  6. #6
    Road Rasher BladeJunker's Avatar
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    Quote Originally Posted by ComradeOj View Post
    Are you using a 6 button controller? I've had a tough time getting input to work correctly on those. Specifically waiting for the button to be released. It should work a lot better on a 3 button pad. The sound test will still be a bit twitchy not matter what though .
    I'm just running it through Fusion but changing to 3 button actually had an effect like you suggested, with 3 button holding the directions actually slow and stops the sound. But it did help a little bit with the text page flipping.

    Quote Originally Posted by ComradeOj View Post
    I was kind of afraid the difficulty would be too high. The difficulty is very hard to measure, since I designed the stages, and probably played through them about 50 times. Hopefully a decent amount of people that play it can make it to the end. I hope it will be amusing when you get to the villain, and see the short dialogue. If I ever do a sequel, I'll probably get some people to play the stages beforehand.
    Okay I'll keep practicing.

  7. #7
    Comrade as in friend. Master of Shinobi ComradeOj's Avatar
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    Quote Originally Posted by BladeJunker View Post
    I'm just running it through Fusion but changing to 3 button actually had an effect like you suggested, with 3 button holding the directions actually slow and stops the sound. But it did help a little bit with the text page flipping.

    Okay I'll keep practicing.
    I would avoid using fusion. fusion doesn't emulate the VDP's sprite collision correctly, and it will cause you to get "hit" and lose a life on the final boss stage, even if you didn't. Gens has the same issue.
    It works fine on real hardware, so it's definitely an emulator issue. The Regen emulator is the only one that runs it correctly.
    Modded consoles:
    Master System (v7040) with s-video & direct AV out
    Model 1 with 10mhz overclock & halt switches
    Model 1 with 10mhz 68010
    Model 2 VA2.3 with unfiltered Mega Amp, & s-video
    Model 3 VA1 with compatibility fixes & s-video
    32X with s-video
    Visit my web site at www.mode5.net
    Or my collection of homebrew Genesis games, programs, and music on SEGA-16!

  8. #8
    Raging in the Streets SEGA.GENESIS1989's Avatar
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    Whelp I guess it's time to stop being an old cruddy fart and finally download an emulator so I can play the game! Gravity Pig has baptized me into the world of emulation! *snort snort*
    "There's nothing to fear, except fear itself"
    http://i1054.photobucket.com/albums/s486/link2link2link/YUZOKOSHIROISAGODNEOSEEDEDITION.gif

  9. #9
    For great justice! Outrunner Tor Landeel's Avatar
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    Fantastic! I find it a bit...psychedelic, but nonetheless it's very cool!!
    ***** トル・ランディール ******
    Cadash Arcade Colors hack:
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    *****************************

  10. #10
    Mega Driven Raging in the Streets cleeg's Avatar
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    Hey OJ, just doing some ROM sorting and found that there is a game on Google play with the same name as this, thought you might want to know if you don't already.

  11. #11
    Comrade as in friend. Master of Shinobi ComradeOj's Avatar
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    Quote Originally Posted by cleeg View Post
    Hey OJ, just doing some ROM sorting and found that there is a game on Google play with the same name as this, thought you might want to know if you don't already.
    Never thought I'd see this thread getting bumped!

    I've actually noticed that game before when googling my game out of curiosity. I think their game may actually be older than this one. I didn't copy them, but I'm pretty sure nobody has tried to copy my unknown homebrew. I think it's just a weird coincidence.
    Modded consoles:
    Master System (v7040) with s-video & direct AV out
    Model 1 with 10mhz overclock & halt switches
    Model 1 with 10mhz 68010
    Model 2 VA2.3 with unfiltered Mega Amp, & s-video
    Model 3 VA1 with compatibility fixes & s-video
    32X with s-video
    Visit my web site at www.mode5.net
    Or my collection of homebrew Genesis games, programs, and music on SEGA-16!

  12. #12
    Nonconformist Hedgehog-in-TrainingWCPO Agent EyeDeeNo76's Avatar
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    "I think it's just a weird coincidence."
    When pigs fly!

    Sorry I'll let myself out.

  13. #13
    Hedgehog-in-Training Hedgehog-in-TrainingNameless One Epyx's Avatar
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    Ever thought about having this properly published on a cartridge with a box and instructions etc?

    If this is something that interests you then get in touch!

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