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.)