Alex H

Hello, The problem is that writing to the port direction register (SWACNT) doesn't have immediate effect on the value read from SWCHA. ldx #$00 stx SWCHA ; zero the ouput register lda #$ff sta SWACNT ; set all lines to output mode lda SWCHA ; read port ; the value read from SWCHA should be 0 but in z26 ; the joystick switch states are returned stx SWCHA ; zero the ouput register lda SWCHA ; read port ; SWCHA now reads 0 stx SWACNT ; set all lines to input mode lda SWCHA ; read port ; Reading SWCHA should now return the joystick switch ; states but in z26 it still reads 0. ; This is what confuses MGD into thinking an AtariVox ; is connected. I believe the following gives the correct result for reading the port: read_port = (SWCHA | ~SWACNT) & joystick_switch_states Where SWCHA and SWACNT are the values written to the port data and direction registers. Hope this helps. Alex

Well .. yes .. and I have no idea when .. Sorry to be so slow on the updates. I am still working on it - latest binary attached. First thing to say is that there isn't much change to the actual game since the last version. The level configuration is exactly the same and the blue section is still impossible to pass. (It's still just test data.) I have added a proper title page, PAL modes (BW/Color switch to change display mode) and several other little improvements. There are more powerups in the works but some aren't functioning right at the moment so are disabled in this version. There is one new powerup to find though. The sound effects still need some work. For a clue as to the mystery "deluxe features" that Rob speaks of, see this thread. Yep, MGD now has speech courtesy of Richard Hutchinson's excellent AtariVox module. The AtariVox also stores the preferred display mode and the top 5 scores, with player initials. The high score table is only available when an AtariVox is attached though - not enough RAM to hold the high scores and run the game. For some strange reason the high score table does show up in Z26 though (something not right with the joystick port emulation me thinks) but it doesn't work right of course. (It runs correctly in Stella.) Anyhow, hope you all like the way it's progressing. Alex mgd_291004.zip

There is no EPROM included with the board. The chip you see in the image is a hex-inverter, required when using a standard EPROMs - the EPROM itself goes on the other side of the board and would need to be soldered after it has been programmed. Boards with EPROM sockets are also available so no soldering is required: http://www.atariage.com/store/product_info...products_id=217 However, the combined height of the socket and EPROM mean that it will no longer fit instide a cart shell, so these are best used for development/testing. I use an Elnec (www.elnec.com) PreProm-02aLV to program EPROMS and the EreProm-01A to erase them. I'm very happy with both products (especially the programmer - excellent Windows software and wide range of supported devices) but they seem to be very expensive outside Europe. (Not that these things are cheap in the first place.) Alex

What sort of English was that? Ah, you know what I mean anyway. Buzz buzz!

I never dig get around to unlocking that on my Protector. A few posts on RGV claimed to know, but none of their tricks worked. Yep, there seems to bee some false information out there. You'll find real answer on my website. Aaron, I'm really liking Falldown - very playable. I also like the fact that despite our games being so similar in concept, they are both quite different. Anyway, great job there dude! Alex

Yeah, it's pretty obvious the heli-pack was an afterthought. I coded most of the stuff assuming that the man would only move downwards relative to the platforms, so putting this in has made things very cludgy. The original plan was to make it timed like the skateboard but I had to deal with the plaform collisions - I took the easy way out and just cancelled the power-up. This kind of made the need for a timer redundant. I actually quite like the way it's potentially endless. I can design the stages to account for this, making some easier to negotiate on foot, thus removing the incentive to try and fly the whole time. It would be great if you and other stella list members could help with optimization--if Alex wants it of course. But as a player, I would hate to see any features go away to fit into a certain ROM size. I would love to have even more options with the game. Let the ROM be 32k or 64k, I just want the game to be the best it can be. At the moment it could fit in 4k and there's still plenty of room for optimization. But there's still stuff to add and ultimately I'm thinking about a cartridge release. I want to include a PAL mode (especially since I'm in a PAL teritory) and it would be easiest just to put that in a different bank. (I'll probably include PAL60 too.) The final ROM will probably be 16k. But if it's possible to trim it back to 4k and still keep most of the game elements then I may enter it into the compo. If I get it done in time, of course. (I have a bunch of Vectrex projects on the go too.) Well I am English, what do you expect? Yes, they have been replaced by the heli-pack now. I agree, it does seem to go against the whole nature of the game, and against the nature of the code. Yet it is kind of fun. But I'm not entirely happy with the way it is, so it might end up being closer to how you envisioned it. Alex

Cheers for the great feedback everyone! I have an updated binary for you to try out. Not too much has changed since the last version. The biggest difference is the addition of a power-up. If you liked the skateboard then hopefully you'll find this fun too. This one makes use of the button too. Also, now you only get one power-up for each set of fruit collected. This of course makes it hard to pick up many within the restricted game length, so I have included a cheat to allow quick access to the new power-up. Just flick the Select switch to change the current fruit. (This of course won't be in the final version.) Alex mgd_160704.zip

You mean how to negate a two complements value (number=-number)? Substrack the number from zero. LDA #0 SCF SBC PUCK_H STA puck_H LDA #0 SBC PUCK_H+1 STA PUCK_H+1 should do the trick Argh, got there before me. I just don't think sometimes.

Yes, it adds 1 by setting the carry first. Sorry, that wasn't the best way to go about it anyway. sec lda #$00 sbc puck_h sta puck_h lda #$00 sbc puck_h+1 sta puck_h+1 Much better! Alex

sec lda puck_h eor #$ff adc #$00 sta puck_h lda puck_h+1 eor #$ff adc #$00 sta puck_h+1 That should do the trick.

Precisely. The fruit is always in the gaps between platforms so on any given scanline there is either 1 sprite + playfield (asymmetric), or just 2 sprites, never 2 sprites and playfield. It should be up and running, yet it might be complicated to find the right spot to enter it. Ah, so you have to click "Easy unsubscribe" rather than "New User/Get Password" to subscribe to the list. That is pure genius! I guess I understand why they use the tag line "We're just better." Alex

I did consider using the button to flap his arms and slow his descent, but I don't want to change the feel of the game too much since it worked so well on the Vectrex. If it ain't broke don't fix it kind of thing. I still have more power-ups to add though so perhaps I'll use the button for something there. I wonder whether a jet-pack might be fun? Or how about being able to jump on the back of a Joust buzzard? (Now this really is screaming 2 players.) Not sure if I can do that though - getting ahead of myself a little here. Agreed, a high score is a must. My best is around 70, but this is only test data and the blue screen (of death) is designed to kill you before running into random data. If you're lucky and manage to pick up a few down-arrows and skateboards at the right moment you might get a little further, but not much. Alex

Thanks Rob, you answered my question before I even asked. Good to know it works ok on the real hardware. No screen rolls, glitches or anything? Yeah, I was guessing that the kind of harsh trip to the copyright screen was just a placeholder. Yes. I haven't really worked out quite what I'm going to do here. Showing a tally of items collected and high score sounds good but will depend on available memory once everything else is in place. Hmm, I'd kind of decided that 2 players wasn't really an option. The problem is displaying 2 sprites and the platforms with colour changes on the same scanline. I would almost certainly have to switch to a 2-line kernel and lose sprite detail, which I didn't want to do. Either that or draw the players on alternate frames. But I do agree that 2 players would be pretty cool, so I shall leave it as something to ponder. Is the Stella list down? I will most certainly subscribe if/when I can. Thanks for all the great feedback everyone. Glad to hear poeple are finding it playable. I'll have a good think about the suggestions and see what I can come up with. I'll continue to post updates here. Alex

Hello people! Since I've already spilt the beans about my new game in another thread, I thought I'd post a little update. For those who don't know, I've been writing homebrews for the Vectrex for a little while, Protector (Defender clone, nothing to do with the Jag game of the same title) probably being the most well known. Anyway, tucked away in the initial limited edition release of Protector was a hidden bonus game Spike Goes Down, a game which is well suited to the Atari 2600 hardware. So, I recently started work on the 2600 version (title tbc) and here's how it's looking so far... I've only just started putting in level data, so you can't get very far. (Blue level will finish you off.) With regard to the collectible objects, picking up 4 fruits in sequence will open up the power-ups. (I haven't drawn the 4th fruit yet, so for now it shows as a bronze question mark). The skateboard increases speed (on the x-axis) for a short time - good for negotiating levels with long platforms/small gaps. The down arrow increases gravity slightly - you need to collect several of them to really feel the effect. The red stop sign temporarily slows the scrolling, the silver question mark doesn't do anything yet. Miss a fruit or power-up and you have to start back at fruit 1. I'll almost certainly change the way this works, and the stop sign doesn't really do much for the gameplay so I'll probably ditch that. All feedback welcome. Alex mgd_090704.zip

Cheers for the pos feedback people. I'll start a new thread when I have an update, rather than muscling in on someone elses. Aaron: I like your 2 player mode. 1 player vs. CPU would also be pretty cool - any chance of this? Cybergoth: I've not been very efficient with ROM usage and have already gone over 4k, so it's unlikely I'll be able to enter it into the mini-game compo. Godzilla: I'd very much like to include music in the 2600 version but it's not going to be easy, so no promisses at this stage. I'll post with an update soon. Alex

Oops! Let's try attaching the binary again... go_down.zip

Talking of coincidences, I just tried your demo and had to post. I wrote a very similar game to this on the Vectrex called "Spike Goes Down". It was the hidden bonus game included on the limited edition Protector (Defender clone) carts. Anyhow, I just started writing my first Atari 2600 game, and guess what game I'm doing? Check out the attached binary...

Just played a couple of quick games on a real Vectrex (VecFlash multi-cart) and I'm liking it! Only got to level 4 so far (never was any good at Thrust) but everything seems to be there, it's well executed and very playable. Thumbs up from me! Alex

I will be releasing a ROM image soon, but it still needs a real Vectrex to run (via multi-cart, VecRAM, ROM simulator, whatever). My games are not compatible with any emulator I have tried. MESS renders a blank screen, outputs garbage sound and the controller buttons seem to be pressed randomly. DVE has the exact same problems with sound/controls but does at least try to display something, although it's still very broken. Perhaps this release will encourage people to hunt down a real Vectrex, or at least prompt the emulator developers to fix them? No. Both games fit into 32K so there would be no cost saving by excluding one game or the other. It's just a convenient way of releasing YASI and making Protector available to those who missed out at the same time. If I'd had another game completed then I probably would have re-released Protector on one cart, and put YASI and whetever on another. BTW, the hidden game "Spike Goes Down" is not included in this version and will remain exclusive to the Limited Edition Protector. Heh, and if you don't like the idea of having the same game twice, then I don't know what you'll make of my current project. It actually requires that you have 2 copies! And 2 Vectrexes! Alex www.herbs64.com (still not updated yet.)

It's a joystick interface for the Sinclair ZX Spectrum.