IRF

(But of course, when he is eventually drawn with his head down the toilet, he is in the correct location - bottom-right corner, bottom half of the Bathroom.)

Fun(?) fact: if you extend the Bathroom ramp all the way down to the floor, and put a hole in the upper platform directly above the toilet, then during the toilet run Willy will run up the ramp and drop through the hole... But will disappear halfway through the fall... then appear suddenly in the toilet. (ie Without visibly falling through half of the height of the room.) This is because the code which tests for Willy's coordinates at the end of the toilet run doesn't check which vertical half of the room he is in.

Doesn't pressing P during the toilet run stop him in his tracks?

I've seen a walk through where various cheat POKES had been applied, and the corruption progressively got worse (until the machine eventually rebooted). So I think other corruption is possible. Perhaps as a kind of chain reaction. (If a guardian or arrow is corrupted at an earlier stage, then when it is drawn with misdirected coordinates, it too could trample across data or code, and cause further corruption.)

I just had a thought - is it theoretically possible to complete the original Jet Set Willy without applying any POKES, not even the four officially released ones? The Attic Bug corrupts the game data and code in unpredictable ways, so unpredictable that the effects are different every time you play the game. Might it be possible in theory that one effect could be to corrupt the list of guardians in both Conservatory Roof and First Landing, creating an arrow which passes along the character row where the items are located in each of those rooms (an invisible item, in the latter case). Were that to happen, then the white INK of the arrow would auto-collect the items that otherwise can't be collected without using the official POKES, and so the unPOKED game could in theory be completed (provided Willy can manage to complete his journey through the corrupted mansion without one of the many other side-effects of the Attic Bug getting him!)

The internal contradiction in the statement did occur to me (JSW vs MM), but then I suppose the in-game tune in Manic Miner doesn't play during the portal air countdown*, so in that sense it doesn't play continuously. (*Except in Manic Mixup. 😉)

I just saw this on a Facebook post: "MATTHEW SMITH! The creator of Manic Miner and Jet Set Willy. Seen back when he was writing games, and then around 2013. Jet Set Willy was the first game to include continuous music (such as music was on the Spectrum) while you played the game, a feat which up to that point was thought to be impossible. He actually wrote Manic Miner on a Tandy TRS-80." It got me wondering - is that claim in bold actually true?

Thanks for those nuggets from the historical Yahoo! record, Danny! So I obviously considered the scenario of a Bonus Room potentially causing lives overspill (and commented on it) before now! But Andrew Broad's comment, as quoted above, foreshadowed it. The only aspect missing from Andrew's early analysis is that, if the in-game music is playing so that the spare lives are 'dancing', then the erroneous attributes in the playing area will cycle through different colours - because they represent individual graphical bytes of the current dancing Willy sprite, interpreted as colour-attributes. And in certain circumstances, that periodic change in colour can affect the gameplay in different ways (e.g. an errant block might briefly - for one in every four game 'ticks' - become/stop being a Fire cell; or the blocks might auto-collect an embedded item - if the rightmost three pixels are infilled for a particular graphical byte, such as when one of Willy's feet is at a certain position, then this is interpreted as item-collecting white Ink!) EDIT: I went down this particular rabbit-hole, and explored it for some time, back in February of this year in the 'Manic Miner: Highscore Challenge' discussion thread.

Or maybe Andrew Broad or someone else from the Yahoo group from back in the day? Didn't John Elliott take suggestions from the Yahoo membership as he went along developing JSWED through several iterations over the years?

I kind of had tongue in cheek when I made the 'Bonus Caverns option' comment. 😜 Although this discussion has led me to speculate that the primary motivation behind the development of the 'No Kamikaze option' in JSW64 was the need to accommodate the gameplay of Manic Miner in the engine, rather than it being devised as a novelty for JSW-style games (though that is a happy bonus).

Oh, and I concur that the item in Shell Shock! can't be collected in the Yellow and Cyan variants (unless you use Cheat Mode!) (And just to point out - in case anyone was wondering - that item isn't present in the Vector version.)

To answer my own questions (after opening up the game in JSWED): First paragraph - No (and therefore also No. Second paragraph - the Up exit from Shell Shock! is set to itself. The skull is crumbly and won't kill you, but Terry can't fit into the gap to exit upwards anyway (I forgot that his attributes - which are what interact with solid blocks to determine whether and where he can proceed - are bigger than his pixellated sprite.)

The item in 'Shell Shock!' can be collected in the Red Version by taking a route through a room called 'The Point of Fear', which doesn't seem to be accessible in any of the other versions of the game. Have you tried looking using JSWED to see if 'The Point of Fear' exists in the other variants? (And if so, are there any items in that inaccessible room which are thus also uncollectable?) Also, what is the Up Exit setting for the room 'Shell Shock!'? (Again interrogation of JSWED - which I don't have to hand right now - can answer this.) You suggest that the upper area (and item) in 'Shell Shock!' are not just inaccessible, but inescapable - but it looks like Terry might be able to jump up into the room above from the area where the item is located? (Depending on the nature of the white skull in the vicinity - it gives the appearance of a Fire cell, which would block upwards progress, but in the next room below there are identical skulls that are just crumbly blocks.)

It's just occurred to me that a specific solution for this problem for the game Terry the Turtle - given the fact that the Terry sprite is less than one character-row in height, would have been to modify the game engine so that the remaining lived on the status bar only occupied a single character-row. That way, twice as many remaining lives could have been fitted in without causing the spillover/corruption that you describe.

How does the Bonus Room feature work in a Manic Miner game, where each collected item in a room (or technically, cavern) is restored when you lose a life and needs to be recollected? If you collect more than two items in such a cavern and then lose a life, isn't there a danger that the extra lives gained could start to spill over beyond the bottom of the status bar, causing corruption of the playing area (as happens in Terry the Turtle)? I think the Bonus Room feature was designed with JSW-style gameplay in mind, where each item can only be 'cleared up' once per game. (I guess that's why it's called the 'Bonus Room', not 'Bonus Cavern' feature.)

The in-game music should change if you can find a way to activate the Cheat Mode but I don't think that has any effect on the title screen tune.

A couple of beneficial game play changes are noticeable from the walkthrough: - The item on the edge of Conservatory Roof is now collectable; - You can safely drop down either side of a rope from the room above, provided you get the timing right (which you can also do because you can preview the room below from above).

I take it that isn't just to have the score routine follow on straight afterwards (sparing the need for a jump), but instead a more profound rewrite? Could it be applied to every bit of the game code which creates a sound? If so, that could save quite a few bytes overall.

I'm guessing from the name that Eddie's Forest is an updated version of (or loosely based on) The Endorian Forest?

That much is technically true, in so far as the room Hidden Chamber is first encountered early on in the game (before Styx) - where only the area to the right of the partition in that room is accessible - and then later on in the game (after Styx, I believe) a pair of teleporters allows you access into the area of Hidden Chamber to the left of the partition, and back again to the same 'zone' (the jungle-themed area - not sure how that works in a sub-aqueous environment but there you go)... ... That's where the problem lies - once you teleport back to an earlier part of the layout, you cannot do anything but teleport forwards again. So a second bite of the Styx Cherberus isn't possible.

However, I have now managed to find a way to collect those two awkward items in Cheat Mode. I manoeuvred Terry to an equivalent position to directly underneath the two items, in another room, and then switched rooms (via the cursor-based JSW64 Cheat Mode room-swap mechanism). That way, I got Terry embedded in the floor directly underneath the items, with his sprite's pixels aligned with the items as much as possible. I then jumped straight upwards. When you are mid-jump, the sprite's INK attribute stretches up through three character rows at times, and since the Terry sprite is only about five pixels high, an attribute collision with the items was able to take place before a pixel collision with the guardian caused either death, or (with Forcefield activated) the switching off of the Draw Willy routine (which needs to be executed in order to collect items). VID_20240430_094214.mp4

Using the JSW64 Cheat Mode, I managed to collect all the items in Hidden Chamber, and all except for two of the items in the Secret Load and Kill Screen. petal_20240430_105805.mp4 The problematic items in the latter are sandwiched in a single column between two static guardians in the middle of the screen. It seems that when you touch a guardian whilst the Forcefield is activated, the game engine doesn't draw Terry as usual, in anticipation of his demise - it's just the death that is curtailed. So you have to wander around invisibly until you are clear of all guardians, and then the Terry sprite reappears. But this means that Terry's INK attribute (I guess item detection in this game is based on green INK, not white?) is never drawn over those two items, in order to allow them to be collected. I did try moving Terry to be positioned over those two items and then switching off the forcefield, but then death occurred before the collection. petal_20240430_095000.mp4

I have interrogated the code for the Yellow Edition. I looked at all the rightward exits from the rooms (at Offsets #EA in each pair of pages across the four banks of room data), but I couldn't find and trace of a room exit that would lead into the Forbidden Holy Grounds at the top left of either the Hidden Chamber or the Secret Load and Kill Screen. I then scrutinised the teleport code (which took a while as I had to re-learn where the teleport data is stored in JSW64, and what format it is stored in), in case any teleporters (other than the ones you already know about) could provide access to those unobtainable items. But alas, no such luck. *** I didn't investigate the uncollectable items in the Cyan Edition because, based on your description, they just seem to be a subsection of the uncollectable ones from the Yellow Edition? *** I didn't check out the Vector Edition either, but if you say that there is no way to be able to drop down into Styx twice during the same game (presumably because the linear nature of the route doesn't allow for that?), then I can't see how you can collect both items (unless a gust of wind can blow Terry sideways as he descends - or I suppose it might be a sea current given the nature of the setting - or unless he can take a fat pill to expand his sprite across four columns!) *** So in summary, I couldn't find a way to obtain any of the 'Forbidden Holy Items', but at least hopefully I have put your mind at rest that you haven't 'missed a trick' in that regard!? [Of course, there is always the JSW64 Cheat Mode...]

I'm sure patches could be devised in JSW64 which replicated both the safely-break-a-long-fall trampoline and the vacuum descent blocks. Even if they involved an adjustment to Willy's air fall counter, etc, based on a check of Willy's coordinates compared against a hardwired value (the air cells just above the blocks in question), rather than recreating generic new block types and associated major changes to the game engine. (Though the latter would be preferable if you wanted to create brand new caverns and employ the new blocks elsewhere.)

Well if you're trying to replicate the original caverns, and since the 'technology' is readily available (via the patch vector system)...