Archive for the 'DOS' Category

25
Jul
17

Catacomb Abyss for DOS

Today’s game is quite unusual as it’s an early FPS game supporting EGA 16 colour graphics. It was released after Wolfenstein 3D in 1992, but isn’t a clone as it’s a sequel to the earlier game Catacomb 3D (1991). Both Catacomb 3D and Abyss were made using a earlier version of the Wolfenstein 3d engine, the first being made by id software for Softdisk and the second by staff at Softdisk using the same engine. So in that sense you could consider both to be a pre-cursor to Wolfenstein 3d technology wise.

The story is fairly simple and is a continuation of the first Catacomb 3d series. Nemesis, the antagonist from the previous game is now obviously dead, but his evil minions that are still around have built a memorial mausoleum in the town cemetery and are infesting the area. The local town-folk obviously aren’t too happy about it, so knowing you defeated Nemesis himself they send you in to clean up.

Graphically it’s quite impressive for EGA, artistically the sprites and wall textures are fairly well done for 16 colours. Performance wise the engine performs quite well under dosbox, which was configured at 3000 cycles which is roughly equivalent to a 20Mhz 386. I’d expect it to also be quite playable on 286 machines with the exception of slower ones. The engine however isn’t perfect, monsters can get close enough to you that they are no longer displayed. This tended to happen when they spawned very close and made it quite difficult to kill them. I found using the Xterminators usually helped. I also noticed that the texture mapping on the walls sometimes appeared a bit off, and that text on the walls was often hard to read. Despite the faults, the game looks nice and is quite atmospheric.

Sound support defaults to the PC speaker, which sounds ok. You can switch the game over to using Ad Lib sound, but the user interface and documentation don’t make it clear that it’s available and how to turn it on. I played for ages before realising there was another option. Once you manage to get it working the Ad Lib sound effects are quite effective, but they are loud and some of them are a little crackly. This could be down to imperfect emulation of the FM chip in dosbox, but I suspect it’s the pseudo-digital sound effects that are the cause.

The levels are quite short, but still big enough you can get lost. They rely on destructible walls quite a bit, which fortunately are usually easy to spot. They hide them as blocks that are different to those around them or a short and easily recognisable pattern. With infinite basic shots you should be able to find them fairly easily. There are doors with keys, but they don’t have a nice opening animation instead simply vanishing instead. Which could be the reason they aren’t used very much.

As you work through the game there are a variety of settings, each with their own graphic style, and typical monsters found there. You start off in the “towne” cemetery and work your way into the mausoleum and then crypt for Nemesis. For some reason not clearly explained you then end up deeper underground and then the segment that I’m up to, the aqueduct. On the up side each setting is fairly different visually, and some like the aqueduct change things up with different monsters.

There isn’t a huge variety of monsters in each level, but they get progressively stronger and have more variety in later levels. The basic monsters use melee attacks primarily, which can be a problem if they get too close. Zombies, which appear in the earlier levels, are not visible until they climb out of the ground. This sometimes happens when they are already too close to see, so you may need to use a Xterminator as moving away seems futile. In later levels I’ve seen some more interesting enemies such as floating wizards that shoot fireballs at you, large beasts, and what can only be described as aquatic zombies that hide under the water popping up every now and then.

There’s only really one weapon, a fireball that you can rapidly fire. You can’t charge it like the original 2d game, but you can make up for that with volume of fire. The two spells that you get aren’t really different weapons, but rather variations on the basic fireball. The Xterminator previously mentioned basically just fires standard fireballs in a circle around you, useful when many enemies are close, or you want to hit one you can’t see. The Zapper essentially just sends out a pulse of rapid fire and is less useful as you can achieve the same rate of fire manually.

Controls are fairly similar to those in Wolfenstein 3d, but not quite as refined and polished. Turning and moving are as you’d expect, but the control turning faster is the tab or v key, which can be a little cumbersome to reach. The alternative is to turn much slower, giving enemies more time to hurt you. This aside the controls work fairly well.

Catacomb Abyss is the only one of the series that was ever available as shareware, consequently it’s the only one easy to download. From what I’ve played, it’s actually quite decent although a little clunky in some aspects like the controls. Still it has great atmosphere and having short levels means you don’t get as lost as you might with something like Wolf3d. You can buy this along with the rest of the series on the Good old Games website for I think about $8 US dollars.

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27
Jun
17

Chopper Commando for DOS

Back in my teens I aspired to create my own computer games and actually made some nifty little games, but I didn’t ever distribute them. Today’s game, Chopper Commando was made by Mark Currie when he was 15 and did make it out in 1990. It’s a fairly simple arcade helicopter game in which you’re given a mission to complete.

It was written with Turbo Pascal 5 using the Borland Graphics Interface (or BGI). The game uses CGA 4 colour graphics at 320×200 which are mostly drawn using the basic line and fill functions from the BGI library. So artistically the game has a fairly simple line-drawn style that does the job. Sound is also fairly basic, with a few simple beeps coming from the PC speaker.

Upon starting the game you select your pilot from the roster, the number of bombs you can carry and finally the difficulty of the mission. Each difficulty setting has 5 unique missions which is chosen at random each time you play. There is a bit of variety in the missions, some are strictly destruction, whilst others involve deliveries or retrieval of items.

Controls aren’t as intuitive as I’d like, but once I slowed the game down I managed to progress quite well with the keyboard controls. To move you tap the direction you want to move and you gain speed in that direction, in order to stop you have to tap the reverse direction until you slow down and stop. It’s not the easiest way to handle controls, but I managed to make it work for me. I tried using the mouse, but that just resulted in a crash (the helicopter not the game), this could be because I was using Dosbox to play.

Destroying bad guys isn’t too hard, there are four weapons to use for dispatching your foes. First is a basic gun that fires forward. I found it best for shooting targets in the air but the bullets also slow down and fall to the ground, so you can destroy ground targets with it. There are also basic bombs which basically behave like the gun without the forward movement, these are easier to use on ground targets. You have the option to use missiles, but I found they were more likely to get me killed so I didn’t tend to use them. Finally there is a mega bomb which has a larger explosion radius.

Chopper Commando is a fairly simple game, but it has a lot of little extra details that make it charming and fun. The game uses a different colour palette for day and night missions. You can eject from a damaged helicopter and run around throwing grenades until a spare one arrives, and after missions there is a short piece of text from the office that makes fun of you when you die, or congratulates you upon success.

Obviously it’s not very technically impressive, but it’s quite fun. I looked for the Authors website, but it appears to be down, but you can find this on the Classic Dos Games website with a slightly updated version that fixes some bugs and source code.

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04
May
17

Snow White’s Voyage for DOS

Today I’m looking at a platform game called Snow White’s Voyage, originally released by Alive software back in 1996. Of course by this time Windows 95 had changed the scene quite drastically, with most developers having abandoned developing games for DOS. The game has fairly low system requirements, needing only a 386 and about 512K conventional RAM, much less power than many late DOS machines had. So this game is a little unusual when put in the context of when it was released, it’s like it time travelled by about 4-6 years.

The story isn’t quite the same as the fairy tale, the game is divided into 9 episodes with only a few being related to the original story. Each episode begins with a short blurb of story text and a legend of the hazards and treasures to collect for points. The game-play itself doesn’t really rely on the story, so you can ignore it if you wish.

The graphics in Snow White are ok, nothing spectacular, but they do the job. I can totally sympathise, as Alive Software is a one-man software company, I can understand how hard it can be to generate attractive graphics by yourself. The graphics engine seems to be programmed reasonably well, as it appears it would work well on retro hardware like a 386. Although there was one peculiarity, the bottom of the previous level appears to be the ceiling for the one you are playing! Fortunately entities on the previous level don’t seem to be active up there (avoiding slow-down). I’m guessing all the levels are stored together in a single lump per episode. This could have been avoided by restricting the vertical scrolling range, or by only using the tile data from the current level. Apart from looking a bit odd the only problem it introduces is restricting your jump height where it need not be.

Digitised sound and OPL music are supported for the Sound Blaster, and some music with basic sound effects for the PC speaker. The music is implemented quite well, although there are no original tunes, I think the introductory tune is from The Marriage of Figaro and reminds me of a Tom and Jerry cartoon where the music was also used. The music resets every time you die or start a new level, which can sound a bit strange, otherwise it’s generally well done. The sound effects are fairly understated but fairly decent for what they are. PC speaker on the other hand is probably best avoided, it’s not the worst I’ve heard, but it’s not the best either.

The keyboard controls follow a fairly standard layout for platform games of the time, so getting your fingers on the right keys isn’t too hard. Basic movement works well enough but I found the jumping mechanic a bit of a problem. Basically your horizontal movement in a jump is about half as fast as your normal speed. The main problem this creates is difficulty in jumping over obstacles that otherwise shouldn’t be all that hard to avoid. There are also some problems navigating up some tiles that are intended as ladders.

Luckily the game has an easy difficulty option that removes some of the more difficult hazards making it much easier (but still challenging) to progress. The enemies aren’t too hard to dodge, but they are deadly accurate with their projectiles which are difficult to dodge. The worst ones being low flying birds that basically drop un-avoidable eggs on your head. Part of the issue is you basically have to restart the level every time you are hit, making any hit at all very punishing. It’s confusing because you have hearts that are like hit points/health in other games. Fortunately the level doesn’t reset when you start again, so bad guys stay dead if you’ve killed them.

Luckily the levels are quite short, so you’re never sent too far back, but being so short and limited in height has meant there is not that much variety in the map design. I did only get to play the first episode however as I played the shareware episode, and I’ve noted that later chapters do change things up a bit. In the lake for instance the game becomes top-down as you guide Snow White around on a raft, in the later stages of the game you play as Prince Charming, so there’s some variety, just not so much in the shareware chapter.

From what I’ve played Snow Whites Voyage is ok for what it is, but clearly it’s not a classic like say Commander Keen. Alive Software are still around, and you can buy this game in a bundle with some of their other legacy titles for about $5 USD which honestly isn’t too bad if you have any nostalgia for their games.

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07
Mar
17

Space Nightmare for DOS

I’m not much good at shoot’em up games, which is why today’s game, Space Nightmare has a completely appropriate title. It was made by a Canadian company called Microdem in 1994. It is odd for a DOS game as it uses some high resolution graphics and what appears to be Mode X using 16 colours. Like most shooters it has a fairly throw away story about aliens coming to steal our copper, but what’s really important is you get to blow stuff up!

Graphics support is unusual for a DOS game of the period. The menus are drawn at 640x480x256 if set to use SVGA and 640x350x16 for standard VGA cards. In game it appears to use 320x240x16 which is essentially Mode X, but it appears to be only using 16 of the 256 normally available colours in that mode. The game does perform quite well mostly, with some of the smoother scrolling I’ve seen in game. There is some slow down occasionally which seems to happen when the game is loading an image for displaying the first time. You notice this especially when it loads larger images like those for the end of level boss. This might not happen on actual hardware, I was playing using Dosbox.

Artistically the graphics are quite nice and colourful, for EGA. There is dithering in some of the graphics because of the limited number of colours used. This could be a technical issue with the graphic engine, perhaps it only supports a 16 colour mode? Did they limit it for speed? I’m sure they could have gone with 256 colours and not compromised too much on speed and being in Mode X it should have been easy. So the decision to use 16 colours puzzles me.

Sound comes from either the PC speaker or a Sound blaster card. I couldn’t test the PC speaker sound unfortunately because the game disables it as an option if it detects a sound blaster, which I guess is fair. The music is ok, although the tracks all sound fairly similar they do fit the theme of a shooter like this one. Sound effects are also ok, although weapon sounds get louder as you upgrade them. I suspect it plays the sound once for each shot in air, so once you’re upgraded it adds the sound from many shots together. It could have been implemented better, but you can turn down your volume as needed to compensate.

When starting the game you get to choose between one of three ships. Dynamite only fires forward, but is one of the faster ships, upgrades simply add more projectiles. Blaster is slower, but upgrades add increasing amounts of spread shots which can effectively blanket the upper screen with bullets. Lastly Cancer fires forward only at first, but upgrades add shots going backwards and to the sides equally. I found Cancer the most successful as it allowed me to combat foes coming from more directions much easier.

The enemies are mostly mobile air units of some type. They will often fire a burst of bullets directly at you, so dodging is absolutely necessary. I found this quite hard as the hit boxes for your ships are quite large. You can end up being trapped by several barrages and can’t avoid taking a hit. This wouldn’t be a problem if being hit didn’t take _all_ your power-ups, which leaves you very vulnerable. Whilst you can take more than one hit before dying, this is severely punishing.

I found this game quite hard, I couldn’t get past the second level after many attempts. This could just be because I’ve never really been all that good at this type of shooter. I think that having more than one life, and not losing your power-ups when hit would have made this much more playable for me. People who are fans of vertical shooters (and are better than me at it) will probably find some fun, as long as you’re good at dodging.

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31
Jan
17

Creating a benchmark: part 6 problem solved!

Quite some time ago, in fact more than a year ago now, I was working on a basic series of benchmarks to test the comparative performance of the Borland Graphics Interface (BGI) versus a hand coded graphics library. I ran into a problem with my hand coded library not working on some of my real hardware. I ran the tests on a Pentium MMX @ 200Mhz and a 386sx @ 20mhz, it ran fine on the newer machine whilst failing on the older one. I figured perhaps I was overloading the older graphics chip.

So coming back to the problem today with a renewed sense of determination, I did some reading. There happened to be a book in the university library about programming VGA graphics, and I noted that all of their code only copies single bytes to graphic memory at a time, I was copying 2 bytes (a 16 bit word) at a time so wondered if that might be the issue. I changed it and the program still crashed almost immediately.

After some tinkering and some basic math I worked out that sprites being drawn near to the bottom of the screen were the cause of the problem. The test algorithm actually allows sprites to be drawn partially obscured by the right or bottom edge of the screen. On most VGA cards this isn’t a problem, but the trident chip in the 386sx didn’t like any pixels being drawn outside of the visible frame buffer. After writing some basic clipping into the sprite routines the program worked all the way through.

I’ve tested 3 different programs on two different real machines (as opposed to emulation). BGIbench is the original program that uses the provided graphics libraries that came with Turbo Pascal, I’ve used it in conjunction with the VGA256 BGI driver. VGABench is the initial lazy implementation of a hand made graphics library, it’s implemented entirely in pascal and isn’t optimised at all. Lastly is VGABench2 which is an optimised version of VGABench using assembly where necessary, and in the case of line drawing a better algorithm. All three programs were coded and compiled with Turbo Pascal 6.0 and use the same basic test code.

Each program performs 7 tests based around primitive functions found in the BGI. Each test counts the number of primitives that can be drawn over a period of 30 seconds. VGABench doesn’t have a function for drawing circles so it has no results for that test. The tests in order: put-pixels simply draws individual pixels a random colour. Filled Boxes draws solid coloured rectangles in a pre-defined pattern. Circles draws a number of concentric circles in a per-determined way. Random lines does what you’d expect, drawing lines randomly. Horizontal and vertical lines are similarly obvious. Finally the sprite test draws a 10×10 bitmap at random locations on the screen.

At first glance it’s pretty obvious that optimised, hand written code is significantly faster on the Pentium, particularly for filled boxes and sprites where VGABench2 achieves roughly twice the output to the screen. I managed a five-fold increase in the rate of drawing circles, which is impressive as circles are the hardest to draw. The first VGA Bench however is not really much better than the BGI and in some tests actually performs worse. You’ll note that the put-pixel tests all come out fairly close in terms of results, this is because there is little to optimise there.

I suspected that the reason VGABench2 performed so well is because the code copies 16 bits at a time instead of 8bits. I tested this out by changing it to copy 8bits at a time and found it was still faster than the BGI, but by a much smaller margin. VGABench2 copying 16bits yields about 156k sprites, but modifying it to copy 8bits yielded about 80k compared to BGI which achieves around 73k sprites. The first VGABench demonstrates how important optimisation is. It copies data 16bits at a time, but doesn’t even achieve the performance that BGI does, managing around 68k sprites.

386sx-20

The picture looks quite different on the 386sx machine, with the performance looking much more even with a few exceptions. The BGI seems to perform comparatively well across most categories only lagging behind in drawing circles, filled boxes and sprites. My first lazy implementation, VGABench seems to lag behind in pretty much everything except drawing filled boxes, which barely outperforms the BGI.

The results for VGABench2 are good, but not as good as on the Pentium machine. Line drawing is basically the same speed as the BGI. Filled boxes achieves about twice the speed, and circles about 5 times the speed, but the sprites are comparatively slower at about 1.5 times the speed. The explanation for the performance of sprites and filled boxes is interesting and is related to how the test is implemented. The filled boxes are drawn in a deterministic way, a grid of 10×10 sized boxes, the sprites are distributed randomly. Filled boxes end up being drawn pretty much always on even addresses, and sprites will be drawn on even and odd addresses around the same amount. This affects speed because of something called word alignment.

The 386sx, 286 and 8086 processors have a 16 bit data bus, which means the processor can access 16bits at a time. The memory is organised as a bunch of 16bit words, so when accessing 16 bits on an even address only a single memory word is accessed, and when a 16 bit access needs an odd address, two memory words are required. This means doing 16bit reads/writes on odd addresses are half as fast as on even ones, in fact they are about the same speed as an 8 bit transfer.

In beginning to sum up the series, it’s important to remember why I started it at all. Basically I remembered hearing many people discouraging use of the BGI mostly because it is slow compared to hand crafted code. The tests I’ve done have confirmed this, but I feel that it’s also shown how a lazy (or poor) implementation can be even slower. My optimised code is faster, but took a lot of time and effort to create and is missing many features that the BGI provides, such as support for other graphics cards, clipping, and other graphics primitives that are more complicated. I can see why many people without the time and know-how would have found it easier to simply use the graphics library provided.

That being said, hand written optimised code certainly has an important place as well. It was pretty fun and challenging to try and make something faster, even though I almost certainly didn’t get my code anywhere near as fast as more proficient assembly programmers. Also it’s hand optimised code that made many PC action games possible at all. Gaming on the PC would be very different without the hardware guru’s that could squeeze amazing things out of basic hardware. Writing this has made me reconsider my stance on sticking with the BGI for my platform game, I probably won’t gain a lot of performance, but I may be able to get it to work on older hardware as a consequence.

Code and binaries are available from the pascal downloads.

16
Jan
17

Mad Painter for DOS

I’ve been away on my usual holiday break and recently got home. Whilst I was away at my parents place it was really quite intensely hot, like 40+ degrees Celsius in the shade. It’s not unusual to get a few days like that where they live, but the heat seemed to linger for longer this year. In heat like that (and without air conditioning) you can’t really do all that much, most people usually just try to keep cool and lie down during the worst heat of the day.

It’s usually a good time to sit and play a game, I usually favour something that doesn’t tax my brain too much which leads us to today’s game. Mad Painter is a fairly simple arcade style maze game. Essentially you are driving a paint truck for your city, painting the road markings as you drive around. You have to paint all the roads to progress to the next level, avoiding a few cars driving around. You’re scored based on how much of the level you paint. I’m playing the shareware episode which only has one city.

The game has EGA graphics and PC speaker sound support. The level is larger than the screen and scrolls around impressively smoothly even on lower speed hardware. In fact you’ll probably want to go for an older 286 machine, an upgraded XT or AT or equivalent cycles in Dosbox. The game runs quite fast even on slower hardware, playing ok at ~500 Dosbox cycles, and probably optimally at around 1000 (about a 286 @ 12Mhz using TopBench to benchmark). Despite this in game speed, the menus and transition screens take much more time to draw and animate. Looking at the graphics in game I wonder if it is using a hacked text mode to achieve the speed, and the other screens use a genuine graphics mode. Sound is pretty basic, but not bad, and you can turn it off if you don’t like it.

The game controls in much the same manner as Pac-man, allowing you to anticipate a turn before you arrive. The maze however is no-where near as dense, so there are fewer places to turn and more potential to be trapped by enemies. Luckily there are only two cars which are however driven by maniacs who speed around like they are driving a super car. It is their speed which makes them hazardous, as they drive randomly and will not seek you out.

Mad Painter serves its purpose well, it’s a fun little distraction that you can quickly play and not have to commit too much effort or time.

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25
Dec
16

Xmas Skyroads for DOS

This year I thought I’d try to get a Xmas themed post out before rather than after the day. To that end, today I’m looking at the Xmas edition of Skyroads made in 1993 by Bluemoon Interactive. It’s essentially a driving game, where you navigate a small craft on the sky roads merely trying to get to the end. Like most other Xmas themed games it is a re-skinned shareware game, but unlike those it is shareware itself with an expanded registered version that you could buy. This will be my first time playing Skyroads of any kind. I’ve heard this one is more difficult than the original, so you should keep that in mind and perhaps play the original first.

The games VGA graphics are fairly well done, most of the detail and artistic effort appearing in the backgrounds for the levels. There aren’t many sprites or animations mostly because of the game mechanic more than anything else. The level scrolls towards you and your ship, and does so quite smoothly, but it lacks any detail (such as texture mapping) it basically consists of coloured shapes. Altogether it’s fairly minimalist, but colourful and attractive.

There are minimal sound effects for much the reason there are few sprites, the sound system mostly shines through its background music, which is pretty good. There is plenty of variety and it suites the atmosphere of the game quite well. Interestingly Bluemoon had quite a but of expertise in making music software for the PC. They had made a music tracker called Sound Club, which clearly had a part in making the music here.

The controls aren’t as well engineered as I didn’t get along with them as well as I’d hope. The key layout is fine, only the arrow keys and the space bar are used, but it feels like there is a mild lag in the game controls, as I continually felt that the game was missing key presses. In this game that’s quite important, as precision is key, especially as the levels are fairly challenging. It affects me enough that even on levels I know and have beaten the problem arises.

Mechanically the game works quite well with a few minor exceptions. Jumping and moving feel nice when the controls respond in time, and the ships behaves in a reasonable way. You can’t change direction whilst in mid-air, and some areas of the level can prevent you from changing direction. The only annoyance is the occasional time you collide with an obstacle or fall off when it feels like you shouldn’t have, luckily this isn’t a common occurrence.

I found Xmas Skyroads a little too difficult, but I’m not really who this game was made for. It’s really for anyone who enjoyed the original and wants a more difficult challenge and on that it delivers. I could only beat a handful of the levels, but that’s to be expected. The Xmas theme is fairly light on the ground, it mostly just applies to some of the back grounds, so it’s quite playable at any time of year without feeling too out of place. Bluemoon Interactive made this and the original freeware quite some time ago, you can find it on their website.

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