Shoot ‘em up in the mould of, well, a shoot ‘em up.
Horizontal Scrolling arcade action.
Your Sinclair review (Recovered) courtesy of the YS Rock 'n' Roll Years YS83
Parallax (SAM) FRED £11.99 Nov 1992
Still waiting for a decent shoot-'em-up to appear on the Coupe? Don't blame you. We've had Sphera (giggle) and, erm, that's about it. But wait! Here comes Parallax - a twelve-level horizontally-scrolling MODE 4 (ie 16 colour) blaster with multiple attack waves, end-of-level guardians, power-ups and just about everything else the ancient Speccy game Sidewize had. Oops... yup, Parallax is, in fact, a Sidewize-alike (except with a dinky spaceship instead of the suited space blokey). It suffers from exactly the same problems as that venerable game - it's ridiculously difficult, being more a test of memory than anything else (you have to know the safe spots on-screen for each of the attack waves); you only get a power-up when you destroy an entire wave; and you lose all your power-ups when you die.
The game also throws in some new hassles of its own. Okay, a multiload is nothing new, but this one's so slow you get an embarrassed loading counter. And when you finally battle through to a guardian and defeat it, there's no big rewarding explosion, just a bit of screen flash. And the parallax scrolling of the title is a mite disconcerting - whenever you change direction, it does too. Makes a fellow quite queasy. (Ulp.)
Right, let's move onto the good points. I loved Sidewize to death (I still think it's one of the Speccy's best ever shoot-'em-ups) and I had a fairly good time playing Parallax. It's a tough test of the old reflexes, and there's a clever option at the beginning whereby you choose the power-ups you're going to collect in the game. The graphics are small but neat, bursting with colour and very smooth, and the music is repetitively passable: a fine backdrop to an instantly playable but un-addictive game.
The trouble is, with all its bells and whistles, Parallax has neither the style nor the variety of Sidewize - the waves get very samey and there are far too many of 'em before you reach a guardian. Before ever so long, you're reaching for dear Mr Reset Button and giving him a firm press. In the short term, it's fun. In the long term, you'll still be waiting for a decent shoot-'em-up to appear on the Coupe.
Disc Protection by Simon Cooke included some hidden demos unknown to the publisher.
There was a bug that caused a crash when some of the later levels were loaded, this was fixed with a patch issued on Fred 25 which also had the effect of disabling the hidden demos.
However, even with the patch applied the following message exists in the code : “HERE, USED TO BE SOME ENTROPY DEMOS - AND YOU CAN STILL GET TO THEM IF YOU POKE THE JUMP JUST ABOVE WITH 16607… COOKIE!”
FRED Magazine reported that this game was originally going to span over three whole disks, but Cookie’s clever algorithms managed to squeeze it onto only one.
From Simon Cooke 12th June 2023
The Lemmings/Parallax Copy Protection
(Christopher John White - this was all a while back, so please jump in and correct me if I get any of the details wrong - memory is fuzzy). (I'm also borrowing Anton's disk track map )
Just in case anyone's interested, the Lemmings/Parallax Copy protection scheme came about because of two things - one, trying to cram more data onto a floppy, and two, trying to come up with a mechanism that wasn't easy to crack.
But ultimately it was a lot of messing around and experimentation.
The Parallax copy-protection scheme was a neat one (Maciej Woloszyk sent me an email at one point telling me that it had taken him longer to crack than pretty much any other one he'd come across - a marathon 24 hours hacking stint). It relied on a few tricks - 1KB sectors (aside from the mandatory 512-byte boot sector/directory entry), loading and overwriting the DOS over the top of itself (obliterating many hacks - and the code to load the rest of the game after loading the DOS only came in while it was being overwritten). But the coolest parts were the sector addressing scheme that made it pretty hard to figure out what the hell it was doing, and difficult to copy, as well as adding extra tracks.
Source code for the copier, and the DOS, and the boot sector can be found here:
Boot loader, that loads the DOS over the top of itself:
First the extra tracks... I can't remember if it was common knowledge or just from experimentation but you could get about 84 tracks per disk on a SAM disk. This was about the limit of the Citizen drives, and it was quite possible that some drives might not be able to read the highest numbered tracks, but hey, who doesn't like to live dangerously? The innermost tracks are also spinning much faster (meaning that you'd need to use write precompensation to write data to them correctly), and there's a good chance that you'd run out of space for the entire track if you weren't careful. But luckily, it seemed to work fine.
The next part was realizing that the address data for the sectors on the disk was arbitrary. When you step to a track, the track register is an optional counter to keep track of what the stepper motor is doing, but only if you set the right bit in the STEP commands on the disk controller. Otherwise it doesn't update. Similarly, verifying the track after a step is an optional step controlled by a bit on the controller.
In other words, checking that you're on the track you claim to be is all entirely optional. So the track part of an address doesn't need to be the same as the physical location that the read head is over.
Sectors don't need to be numbered from 1-10 either. You can number them anything you like. So let's number them entirely differently.
Once you've done that, all you need to do to read back a sector is to set the TRACK and SECTOR registers to match whatever you want to read from under the head as it spins past (the numbers can be anything), and then do a read sector command.
I hacked together another copy protection scheme based on this at one point but never put it out into production. The idea was that you'd have multiple sectors on a track with the same address, but one would be full of garbage. You'd have to get the timing just right to read the uncorrupted sector in as it went under the head (probably by reading the index pulse to get the timing right), otherwise you'd have a 50:50 chance of reading garbage data. Hard if you're duplicating a disk the normal way. (Also tempting to do if you could fit 11 512-byte sectors to a track, because then a simple disk copier - even one written in BASIC - would see valid files, which would copy correctly, but they'd come out as garbage... spoooooky...).
The Lemmings copy-protection scheme was designed to cram more than 800KB on a disk, and be mostly uncopyable. I'd figured out from a few experiments that you could probably fit 5KB per track using 1KB sectors, plus some room for a single smaller sector if you reduced the inter-sector gap size when formatting the disk. You can't write out a track in a single pass with the VL-1772-02 due to a weird bug in how it handles data (MFM/FM PLL/encoder issues for some bit patterns), so you need to leave enough gap that you don't trash the sectors to either side with bad writes when writing out the disk in the second pass. This limits how much you can cram on, but it ends up that if you use multiple sector sizes per track you can cram an extra one in.
Using the largest sector size for the majority of the sectors also reduces the amount of space needed for track headers, gaps, synchronization marks, and so on - increasing the space. Which is why you can't fit 11 512-byte sectors on a track, but you can fit 5 1KB sectors and 1 512 byte sectors.
I didn't implement this for Lemmings (IIRC), but told Chris, and Chris took some of the Parallax DOS code for reference and the E-Copy copier source and went ahead and hacked it in. Chris went a bit more conservative for Lemmings and reduced it to 82 tracks per side to make it more compatible with more drives in the wild. (Although we had no hard data on compatibility issues, AFAIK).
To access the hidden demo (if not patched), you’re apparently supposed to hold down keys P, U, R, G and E at the title screen. Purge: No Way Back II was the name of an earlier but unfinished BASIC shoot ‘em up (Demo on Fred 11) as a sequel to ‘No Way Back’ on Fred 8.
I fact I never managed to get this to work. My disk is dated 1995, so maybe the publisher removed it from later copies. Ironically, even if you can find a disk with it included, it will probably never work in SimCoupe since most modern keyboards can’t register five keypresses at the same time.
In the ‘Hidden Demo’ it suggests pressing ‘E’ ‘D’ ‘G’ and INV.