Release Gravity Force

[NoeleyC]

I got nostalgic after reading this thread so I downloaded a few old Amiga Power cover disks, including Gravity Power! It's two player only, and because the ships shots are only one pixel big, they're nearly invisible on the Pandora screen(maybe my choice of screen resolution affected it!) other than that, it plays great!


(null)

 

[lomaxx]

On level 11 there is a ceiling-shooter that starts to shoots if the players position is close and higher than itself. However due to the level-design that doesn't make sense. So i assume that this is a bug.


Btw: Did you write your own routines/parameters for the calculation of ship-slowdowns and gravity-effects? If not, then leave things like they are. I don't wont you to taint the original game-play. Otherwise my impression so far is that the left-right-slowdown is a bit too strong and that drop-down-speed does not increase enough. The ship seems to float down and not fall down if you leave thrust away completely. This is especially rather unrealistic when you are fully loaded with cargo. Unfortunately i can't recall what the original gameplay was like.


Oh, and keyboard-entry for highscores would be nice. I mean: We own a Pandora with keys!


Anyway: It was and is a good, simple game and i like your remake/clone, although I already start to hate level 16 - as i probably did more than two decades ago.


Edit: Another proposal: When selecting the level it would be nice to be able to go from "0" to maximum level by pressing left. I'm on level 22 now. Is there any way that i can help you porting the remaining levels 28-50?

 

[Dave18]

Thanks for the feedback, level 11 definitely sounds like a bug and I'll look into it. I wrote the ship routine but based them on the original which is also quite unrealistic but I'll take another look in case I've overdone it.


To create the levels I need a 336 x 800 picture of the level made up from screenshots taken from uae. Uae screen resolution must be set to lo res with no line doubling (you have to take 3 or 4 shots and paste them together). I have a routine that turns the picture into tiles but the source picture needs to be pixel perfect. If you want to send me any levels it would certainly speed things up (maybe just one to test first). Use warpxx as a password on the original to select levels.


Dave

 

[lomaxx]

Few more small bugs:


- The last level (26) can not be selected. It stops at 25. This might be intentional, but I find it more likely to be a common +-1-mistake of coding.


- The background-collision-detection is a little bit inaccurate. This leads to an increased difficult in aiming at some wall-turrets. I noticed this first in level 16. You can see this flaw quite easily if you select level 03 and look at the first 3-shot-turret. I compared this level to the amiga-version. There the turret's bullets fly in all three directions.


- The life-counter of your remake differs. The amiga-version starts with 5 ships and the game ends when you crash with "0" ships left. In other words it shows the amount of extra-ships. In your remake the game ends when you crash with "1" ship left. The counter shows current ships. So the player has one ship less.


- The title-image of the game is missing. I attached the image. Edit: The image has 2x-size. If you prefer the original 1x-resolution, then launch gimp, resize and choose half the height. Width should apply automatically. I also set interpolation to "none" to be sure nothing changes 'between' pixels.


I will try to get level-screenshots done. But I am having some very strange issues with uae (both p-uae and e-uae). It used to work several months ago (not sure how long ago it has been), but now that i tried it again the performance sucks and the gui is going nuts.

 

[lomaxx]

Here is level 27. I decided to leave the enemies on the image for now. So far i removed the playerships and bullets. If you want to have the enemy-ships, -tanks, -turrets, fuel and cargo removed as well, then let me know. Note that the enemies position and number are not representative due to the merged screenshots.

Spoiler

Please also take a moment to think about anything else that might be required. I'll start mass-production once you reported back.

 

[lomaxx]

Well ... I couldn't resist. Here are the missing levels (27-49):


http://userpages.uni...ce-shots.tar.gz


Tell me if you want more modifications of the images.

 

[Dave18]

Wow, thanks! I'll take a look and try to get them converted as soon as possible.

 

[Dave18]

I've updated Gravity Force in the repo, changes are:


All 50 levels now included, thanks to Lomaxx for providing the pics to help me do this.


Improved inertia and speed routines (as per Lomaxx's suggestion)


Improved gun turret firing routines


Improved bullet to background collision detection


Fixed life counter


Added keyboard hi-score input


Added splash screen


Added remembers last mission on menu screen and left at zero will go to highest avalable


Any further bug or comments on the changes let me know


Dave

 

[lomaxx]

First of all for the 50 levels(!), improved gun turret firing routines, improved bullet to background collision detection, fixed life-counter, keyboard-input for highscores(!), splashscreen and the remember the last levels+left=maximum(!)


Thank you! Thank you. Thank you. Thank you. Thank you! Thank you. Thank you!


These are great advantages.


Now for some more things. I hope i don't annoy you.


- level 06 is bugged. A turrets moves around when the screen scrolls. I din't play much more levels yet.


I again compared the amiga-version with your remake:


- fuel consumption is too high. While i have ~89 fuel level when finishing level 1 of the Amiga-version, I have only ~65 left when i do the same in your remake. Also i noticed that in the A-version you do not get 99 fuel on a level start. But still when you die. This makes the fuel-containers much more interesting.


- left/right-slowdown seems nice now


- gravity is too strong. That might be my fault as i didn't accurately describe how the ship behaves on the Amiga. On the Amiga the gravity is (as already said) a considerably lower. Without thrust the ship slowly gets faster up to a speed that i still would describe as "floating down". But if you thrust downwards it still get's faster.


With cargo and without thrust the ship accelerates faster and up to a higher maximum-speed than without cargo. Thrusting down increases both (i think).


Well - I must admit it's hard to compare. Also I am not sure if my emulation is running at maximum-speed on my computer which might make it harder to compare. But one thing i am quite sure about is that in your version, if you thrust down, and then stop thrusting down, the ship magically slows down again at once.


And one last thing for now: Could you map the Y-Button in the menu to "start game", too (parallel to the "start"-key)? The start-key is somewhat out of reach. The Y-button more comfortable, but still i would leave the start-key active.


In any case: Thanks again! I will report back if i find more bugs in the levels.


Ah wait: I still have a question left. How do you implement the flight-paths of the ships? By observation of the Amiga-game and rewriting them manually? That would be quite some work.

 

[lomaxx]

Blah, the more I test, the more unsure i get how much gravity should be changed. :/ Maybe test without sprite/background-collisions would good. letting the ship drop from the topmost position to the bottom of the level with and without cargo and stopping the time. Don't feel pushed by me to spend a lifetime on this. It's already quite okay.

 

[Dave18]

I'll fix the fuel consumption and level 6 bug and release another version soon.


I've also changed the code so if you stop thrusting when flying downward it gradually returns to 'floating' speed rather than instantly.


I had to implement the flight paths by observation and manually copying. Most time they run around a loop so I made it so I could just choose the top left and bottom right corners and it would work out the rest (and also snap the coords to an 8 x 8 grid). It took a while to recreate each level but you halved the work by producing the png files for me.


I'm am currently looking into getting two player working over a network connection. It's my first foray into networking so not sure how it's going to go.

 

[lomaxx]

Few more minor differences and thoughts ment as inspiration:


- In the A-version crashing results in the loss of the autofire-powerup, but you keep the powerup if you make it to the next level.


In your version it's the opposite: you die -> you keep it, you finish the level -> you lose it


- In the A-version you can shoot the shots of the enemies. Actually this is really unimportant, as the chances to do that on purpose are very, very low.


- Is there a pause-mode in your game?


- Is there a mute-button in your game? (ok, you can turn down volume, but you might want to play with a mp3-player in the background and without the shooting-sounds.)


- I wondered if it's of interest to have to unlock the levels in packs of 5, like in the A-version. There you get a password every 5 levels and until you got that you have to start with the password before or at the start. As you got the level selection implemented, this would mean that e.g. you have to make it to level 5 ( or 4?) to be able to select level 0 - 4 (erm, or is it level 1 to 5, ....confusing) and so on.

 

[Dave18]

I've uploaded an update to the repo.


Fixed:


Fuel consumption


Fuel refilled on level completion


Added:


Best level selectable only increases in batches of 5


Pause - Press P (disabled in online mode)


Preliminary online two player support


Note about online mode:


I've only tried this over my local network using a version compiled for windows as the second player. If I use the windows version as host it runs ok but using the Pandora as host is very slow. I've only tried it using the Pandora's internal wifi which is pretty slow so a USB wifi stick might improve performance. I've attached the Windows version for testing purposes (although it's fully functional - default keys are the Pandora equivalents).


The host will have a number of the top left, this is how many millisecs the host is waiting for a reply. It can be adjusted using the 1 & 2 keys. Any feedback on what values work bet is appreciated.


The networking basically sends keystrokes which means that each frame must be kept in sync, even one missed keystroke can cause huge differences between the two versions. This means that if a lot of packets are lost the game will slow down while getting back into sync. Enemies that are on preset flight patterns will be the same for both players but tanks (the green things) and enemy shots will be unique to the local machine (for this version at least).


Edit - forum won't let me upload windows version - I get 'Error You aren't permitted to upload this kind of file'. PM me with you email address if you want a copy.


More edit! - changed from rar to zip and uploaded fine.


All feedback appreciated.


Enjoy


Dave

GravityForce.zip

 

[Dave18]

Lomaxx, have you had a chance to try out this new version? Hopefully it plays more like the original now.


Dave

 

[lomaxx]

I didn't play much more yet. Christmas consumes too much time for consumption of food and drinks. And then there are all these relatives that weren't supposed to appear. Additionally there have been a lot of other releases that I fiddled around with. And last but not least I wanted to leave you in peace during these stressing days.


What did I do and what not: I didn't test network-mode since I got no own windows-pc nearby and there is no one who would want to play with me anyway. My own interest in challenging others is low too. But I made a quick game to see if the gameplay (mostly regarding fuelconsumption) is at least good enough to make it to level 5. It is. Although I find your remake considerable harder. For a 100% comparison I still would need a decent PC in order to be sure that emulation is fullspeed, but it seems to me that in your remake the ship turns faster and thus landing is not that easy. Also I'm still not sure about the gravity- and thrust-balances. I don't want to judge that without taking a closer look again. If i remember right, then the ship still slows down, after thrusting down more than the original (if that slows down at all).


I must take another look soon.

 

[lomaxx]

Very small thing: Sometimes I launch PNDs from a terminal by entering "pnd_run <path_to_pnd>/<pndname>" and so far this always worked. Your PND is the first that i noticed where by default the documentation launches instead of the game itself. I still can run the game that way by specifying "-X 1" at the end, so this is just a very minimal bit of inconvenience, but if you fell like it you could swap the positions of the documentation and the game in the PXML-file. Not worth an version-update itself, but could be implemented with a future update.


I will enjoy some more GravityForce now.

 

[lomaxx]

I played the 5 first level again without dying in order to test fuel-consumption. I think the left fuel was at 37 when i reached the upper fuel-tank in level 4 and i didn't really try to safe fuel. In the Amiga-version I made a quick game to the same level and entered the level with 07. This isn't a very precise comparison, but I think you can increase fuel-consumption by 10% for now. Although this balancing might also change in case you modify the gravity/thrust-mechanism.


Also in the Amiga-version a fuel-container gives just 50 fuel, not 100.


Additionally I noticed that the backspace-key does not work when entering your name for the high-score. Cursor left works though.


Still I am struggling with setting up a decent Amiga-emulation. Tried the uae4all on the Pandora, but for some reason i can not make the game run. It hangs after starting a game, when a level is supposed to load.

 

[Asmo]

Very nice, gravity games just never get old.


Not meaning to take any of the limelight from Gravity Force, which is great, but because it's something any Win PC users who enjoy this genre may have missed out on, Neon-powered "Thrust Xtreme" ( Download ) is a joy. It's vector graphics and gameplay are just sublime.

 

[lomaxx]

I played some more GravityForce. Reached a new highscore of 3670.


These are the notes i took this time:


- In level 13 you can shoot the two cargo-boxes at the top of the level. I think it's the right, large box that causes an exploding sound when shot, but the box does not vanish so this is a minor bug


- Also in level 13 I noticed that the range of the magnet-wall is too short. I compared it to the amiga-version level 13. There ,no matter how close i stay to the left wall, I get attracted by the magnet-wall. I don't know if the magnet-walls always have the same range or differ from level to level, but in that level 13 it's too short.


- One time while playing I was hit by a bullet but not destroyed if I don't remember wrong. The only logical explanation I had was, that maybe the flame of my thrustengine blocked the shot. I tried to achieve this on purpose, but didn't manage to get it done. Anyway, this is so unlikely to happen, that it doesn't really need to be investigated.


- In the Amiga-version you crash when you land on the debris of one of those green tanks. In your remake you can land on (behind) it.


- I tried to compare the ships-control of the two versions by doing a "turn-launch", meaning that when landed, i push the joystick/pad into one direction and then thrust. On the Amiga-version you most of the time manage to start that way without crashing (only when no cargo is loaded), although sometimes (rarely) you DO also crash. In your version the ship hangs for a second or so. You manage to start when turning left, but always crash when turning right. This difference is probably also related to the gravity-differences (see below). I just write this as a side-note.


- maximum drop-velocity seems to be ok. At least it's the same for your ship and for enemy ships, just like it is in the Amiga-version


- acceleration cause by gravity is quite a bit slower on the amiga-version. I tried to compare it to the background-graphics. On the Amiga I believe to have noticed a length of roughly two screens until the maximum velocity is reached. In your version this seems to be the case after less than one screen.


- turning speed is a bit lower in the Amiga-version, which i think is better as sometimes putting the ship into position for landing is a bit awkward. I tried to compare both versions in level 16. From the top of the rightmost, long shaft to the bottom of the level, i managed to do nearly 12 turns with your remake before crashing. In the amiga-version i managed to do 12 without crashing, (but it still was close to crashing). Also keep in mind that in your version acceleration is higher so the overall time i had to the turns in your remake was shorter.


- When thrusting down in both versions the maximum-speed gets quite high. Not sure if it's the same in both, but should be fair enough. However in your remake you still slow down to normal falling-speed a lot faster when stopping to thrust downward. I think you can at least set break-down-intensity to half of what it currently is. But this might also be related to the differences in gravity to some extent.


Overall i think your remake is a bit harder. By carefully reducing gravity and turning-speed this should get closer to the original-version.


As a reminder the things from the last post:


- fuelcontainer from 100 to 50


- backspace-key in highscore


- adjust fuel-consumption. If you decrease gravity then I think you can at least reduce it by 10%.


Again: These are just proposals. It's completely up to you how close you want to get to the original version. =)

 

[Dave18]

Thanks Lomaxx, I'll adjust for next release.


Now I've got a USB wireless adaptor I can confirm that you can host using the Pandora this way. Internal wifi is a bit slow though (although seems ok for client).


Has anybody tested online play in anger......? *ahem* Milkshake *ahem* (as you requested it).


Dave