Development Diary - Subterranean Stryker

27th July 2001:
I am thinking about doing another remake, this time of Subterranean Stryker. This game has been described as 'Defender with caves' and was published by Insight and written by Mike Follin.

This game would be infinitely more complex than Lunar Crabs in many respects. It had a scrolling upper section, a map at the foot of the screen, shields, fuel, about 5 levels and an actual aim to play for. So much more than left/right shoot !
The original game was almost impossible to play, even the author said so in interviews, in fact the last level cannot be completed.

I wanted to check out the levels and game play before I decided if I could actually do a re-write. I searched the internet for pokes to help me with this, but only found an infinite lives poke. More searching, and I found the Spectrum Software Database included a poke to change start levels (65535,n). At least now I could begin on any level, but the game was still infuriatingly hard to play. How anyone can actually fly around levels 4 and 5 are beyond me!!!

I located Mike Follin's web site and sent him an email asking if there was any other pokes that could switch off collision detection. Unfortunately he said he was un aware of any, but pointed me in the direction of some pointers in the code.

I loaded up WinZ80, fired up the debugger and stepped through the collision code (very slowly). After about 2 hours and many crashes, I found a poke that stopped the shield from being depleted on contact with the caves. (65793,0) This does not stop collisions with aliens, missiles or the 'deeper' rocks.
(for those interested, the outer layer of rock allows minor collisions that deplete the shield. The inner layer kills you)
It does how ever, make the game easier to play, and more importantly, to map.

30th July 2001:
I quickly put together a test app to see if I could get the two levels working together (top scrolly bit and real-time map). I managed it, and was pretty pleased with myself. I only used blocks for the graphics - so nothing really impressive to show. The important thing was that I could manage the screen handling, hopefully the other stuff will fall into place later.

Got an email from Gerard Sweeney in reply to plee for help. He said he would try to hack the game and come up with a method of seeing all the levels without having to actually play it. (Invincibility!)
I poked about a bit more and discovered some more pokes that let you fly through walls. Unfortunately they leave a trail behind the ship, but at least I can map the levels now. I found a few other problems with the pokes after more testing, they cause some sprites not to be displayed (not good for mapping!) and the game crashes if you get killed.
If Gerard doesn't come up with something, I will have to guess the sprite placements on the last 2 levels !

2nd August:
Dug out an old copy of Crash (ish 14) and read the review. It claims there are 8 levels, but the game only appears to have 5. I emailed Mike Follin (original author) for confirmation on this, along with a few other questions like where the hell is the crystal that you're supposed to locate and destroy to complete the game. I couldn't see it on level 5 (but then again - many of the sprites vanished because I was using the above mentioned pokes!) - unless there are more levels !!!!

4th August:
Using the above three pokes, I began to map out the first level.
I made a copy of the original lower map, and stuck it in the code. Using the real-time map and flashing dot (representing your ship) I began to build the first level in the upper section of screen.
A quick visit to the garden with the digital camera, I found a nice looking rock, took a few snaps from different angles, dumped them to Paintshop, reduced them and generally buggered about with them to produce several lumps ready to put into the game.

6th August:
The rocky bits of level 1 are now in place and scrolling about. You can now fly your bright yellow triangle through (literally) the caves, following your progress on the map. Added a shaded sky and a similar thing behind the map. Produced some trees and plants to populate the caves. Still no collisions yet.
Drew the player ship - looked ok for a first attempt so I'll leave it in.

Got emails from both Mike Follin and Gerard Sweeney. Mike confirmed that there are only 5 levels, and that the crystal may only appear if you have completed all previous levels (sneaky!). He also reminded me about the speech (via Currah). I loaded WinZ80 again (the only em that supports it?) and played a bit. There are quite a lot of vocal effects to consider.

Gerard did some marvellous work and supplied me with a hack that lets you fly about impervious to caves/missiles/aliens etc.. and still collect men to allow access to the next level. I will be looking closer at the levels now.

Here is the first picture of level 1 compared with the original. Note that some of the trees and stuff are different, and that the cave does not continue through to the left and the name is spelt wrong.... and.. and.. loads of things that I havn't done yet....(image reduced to fit!)

August 9th:
Put in the collisions with the cave walls. It now plays a nice 'clang' sound when your ship hits something solid.

Now this is working, I drew some pics for the fuel and shield meters, only dull things for the time being, I will do better ones later. Dumped them into the game and thought of ways I could deplete them in code.
Eventually I cheated and overlayed a black sprite that is moved over the meter, giving the appearance of the shield being reduced. (hey! It works!)

I linked this to the collisions and now each time you bump into a wall, you get a 'clang' and the shield depletes.

Mike Follin noted that the game would be nice with wider caves to manoeuvre and some momentum to the ship. The caves are bigger, and I've put a tiny bit of momentum in there. I will see what reactions I get from the beta about this.

At the moment, the black sprite just keep on going - right across the screen and off the other side. I need to put in a routine to blow your ship up when its down to nothing. But first I need to draw an explosion.

I am hoping to get the first level out as a kind of demo/beta thing very soon.
Drew an explosion. I patched it in, wrote some bits that detects when the shield is zero, and then blows your ship up. Flying about the caves is great fun, and much easier to navigate than the very tight originals.

Added a few mushrooms and drew a little man digging. (these are the captives you have to rescue).
I placed a few about in the caves (same locations as the original) and added a routine to pick them up.

August 20th BETA 1 RELEASED
Added a few more aliens and stuck them in their correct places around the cave.
Added a proximity check thing, so when your in range, an alien will shoot at you. It seems to work well, but the aliens can seem dumb at times. I have limited the number of alien bullets to 4 (at any one time) at the moment.
The first level is now quite playable. There is no game-over routine yet, but you can get killed by running out of shield or by hitting an alien, or by being shot by one.

Did some tidying up on the cave layout and tweaked a few things. Put the remaining nasties in position, checking with the original to make sure I got it right.
Finally added a game-over blank screen thing, and a crap intro screen.
There is a lot to be done yet - but I have a fully working version of the first level now, so here it is to download. Your comments are welcome.

Remember, this is just a beta to get feedback. Once all the game 'mechanics' are tweaked, then the other levels should only involve sticking in more graphics and adding the maps etc.
Things I have yet to do (so don't email about it).
1) Sounds when moving your ship
2) Voice effects???
3) UFO (like the original) that appears if you spend too long on a level.
4) Better shield and fuel meters.
5) Change the name on the bar.
6) Markers for men on the lower map
7) The other levels !!!
8) Music?????
9) Loads of tweaks....

August 25th
So, onward.
Level 2 begins with another foray into the garden in search of a suitable rock to photograph. Finding a nice one, I convert it into useable blocks before heading off to the original game to grab screenshots for the map.

Having created the map, I began work putting the blocks into the play area. I am not sure about the rock I used on this level, I'll see how it turns out.

Level two also has a refuelling depot, so I will have to get the fuel gauge working too. Level 1 is just a kind of introduction level, from now on the levels get increasingly harder, so fuel is required to complete them.

Having noticed how slow this page is to load, I added a screenshots section at the top and replaced any images with links. Hope this doesn't inconvenience anyone !

August 31st
Level 2 is now quite far advanced, although I'm still not convinced about the rocks on this level. I will have a look in the garden for something better.

The play area is complete, some of the nasties are in place and I just have the fuel gauge to sort out.
The map at the bottom of the page does not display the men or the aliens, don't know whether to alter this or not?

The fuel gauge is similar to the shield but has different timings. I got it sorted out and it ticks down nicely now.

I added the routine to refuel when the ship comes into contact the fuel nozzle.
I added a nice subtle engine sound when your ship moves.
Added some fossils to the rocks.

5th September
Level two is now fully playable but may make it harder at a later date.

I played a bit more on the original, and mapped out level 3. The lower map has been created and yet another stone from my garden has been photographed and prepared. This one is much better than level 2, so I still may re-do level 2 completely. Because the layout is done, it will only take about 4 hours to completely replace all the graphics.

Looked into some music for the intro screen and found a great XM module. I tried for ages to get this working, and in the end gave up. I replaced it with an equally good (if you've got a half decent sound card) midi file. I am happy to use this, but first I will have to ask the creator if it can be used.

10th September
Level 3 is coming along nicely now. The levels caves are complete, but some minor re-working was needed to make the game playable. The original had impossibly tight tunnels, so I have widened them a bit, and as a result, the cave has changed very slightly in layout. The aliens are in place, the collisions need a bit of tweaking, and a bit of work is required on the real-time map. Looking good though.
The author of the midi tune I mentioned above was Bjorn Lynne (www.lynnemusic.com). He has kindly agreed to let me use it in the game - so now we have some music.

17th September
Level 3 complete - phew. Havn't had a great deal of time to look at the game recently, so not much progress. I did bits when I could and stayed away from the heavier stuff. So I managed to do a better middle bar thing with the correct name on it, better shield and fuel displays, and few minor tweaks that I can't quite remember !
I hope to make a start on level4 soon.

24th September
Work begins on level 4. More stones from the garden and a quick look at the original using the pokes.
I created the lower map and began work making the actual caves. Again, because of the impossibly narrow tunnels on the original, I have had to make some changes to make the game work better. I doubt anyone actually played the original this far, and even if they did, a slight change in the cave layout would be the last thing on their minds. The main caves and buildings are in place, the obstacles are in, so are the plants, mushroom and men. Didn't have much time for grabbing pictures, but next update I will make sure there's something to look at.

30th September
Level 4 finished. It looks brilliant !
I just have put the aliens in place and added a few collision detections.
I had to spend ages tweaking the lower map to make it fit the actual screen again.
I went back over the previous levels and tweaked them a bit.
Also got my partner to do some test vocals to see how they slotted in. They sounded cool after some tweaking, so I will re-do all the vocal stuff soon.

Here as promised, is a picture of level 4. Checkout the new bar and meters.

6th October
Level 5 begins with a quick look through the original and all of the stuff that’s in there. I notice that the original threw all of the obstacles from the previous levels in here, making it a very taxing stage. There’s some new stuff here too, like the pipe spewing chemicals and best of all, a subway train !!

Another thing I noticed on this level, but was also on some other levels, was the obstacle that you had to fly through that caused a shield hit. This level has loads of them, but I will cut them down a little as my shields deplete more than the original.

Drew the stuff I needed, including a nice train, and began work on the layout.

Yet again I had to slightly modify this level due to the tunnels on the original, but not much has changed. The original is really packed with obstacles, so much so that is was far too difficult. I cut them down a bit to make the game slightly easier to play.

October 21st
Still unhappy with the stones used for the caves on level 2, (compared to the other levels), I went in search of something in the garden to photograph. I found one at last, and soon had a collection of stones ready for the games. I replaced the whole level’s cave system with the new graphics, and it now looks much better. This was a long process, so the game hasn’t moved forward.

October 29th
I tried to get my head around how to place some markers for the men on lower map, and make them disappear when their play area equivalents are collected. I tried out a few methods and settled for one that seemed to work the best.

Level 1 now has the markers working and is complete except for the vocals.
I will work my way through the levels one by one, doing all the tweaks to complete the levels.
I have yet to decide what to do for the end sequence…
Found a bug in all levels that didn’t check collisions with the force field – meaning that all you had to do to complete a level was fly through it !

Re-did the vocals for all (as far as I could tell) of the original Currah stuff.
Level 1 and 2 are fully complete now, and I am working on level 3.
Still haven’t got an idea for an end sequence yet.
Souped up the intro a bit, with some nice graphics and the tune from Bjorn. It now looks a lot better.

November 3rd - Yippee!
Created a sort of end sequence, which on paper looks great, but the graphics are a bit of a let down. Added another tune by Bjorn to accompany the end.
Went through each level – playing it and making a few mods to improve game play.
I now know that each of the levels can be finished – although level 4 is very hard (for me at least).
Did a few minor tweaks to the intro.
I suppose this is now officially beta 1. Lots of play testing ahead….

November 9th - Nearly there...
More play testing of beta 1.2... nothing much to add ....

....coming very very soon.....

November 19th - Version 1 Released.
Yep its ready. Grab it now and let me know what you think.