IRF

The ability to slow the game down would be useful for the room 'The Garden' in JSW2 [original version], the crossing of which requires a succession of well-timed, pixel-perfect jumps.  :o

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 walkthoughts were possibly (likely?) mine, I've done several.
Certain rooms however when the bug is in effect do seem to make it deteriorate a bit faster, notably "Inside the MegaTrunk" , staying here and switching emulation speed up a bit (200% is fine) you'll see the status bar start to corrupt. Kitchens can have a similar effect, although the guardians moving horizontally at that stage is erm distracting.
 
A sidenote about the other "big three" bugs: I think half or most of the battle is Banyan Tree, if it were possible to jump from the left side and catch onto a water cell without hitting a guardian, you could then climb it. The "First Landing" object something would have to be done or the item count adjusted to ignore it, same perhaps as "Conservatory Roof"

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 corrupted guardians can cause corruptions themselves, but in an unpoked game Willy would just instantly die on entering those rooms preventing the enemies from corrupting the game further. The cheat POKEs in the video I saw were to prevent deaths from guardians, allowing them to cause further corruption.

Could it be possible that those cheat Pokes have corrupted the corrupted parts even more?

The effects aren't unpredictable and aren't different every time you play - the arrow's trajectory is consistent and writes to the same bytes every time.
To be precise, it corrupts the flying bird, UFO, Esmerelda, giant head, skull, sunflower, and Andre enemies, and any room those enemies can be found in result in the guardians being misplaced and (depending on the room) embedded into walls (which automatically kills Willy on room entry). None of those enemies can be found in First Landing, The Banyan Tree, or Conservatory Roof, the rooms that would need changes in order to make completion possible.
It's possible to complete Jet Set Willy without fixing the Attic bug, though - you can apply the other three POKEs (42183,11; 56876,4; and 60231,0), play the game as normal making sure to only climb the East Wall and get the items in Priests' Hole and Dr Jones and head into the Attic once you have all of the other items. From the Attic, you can go Under the Roof -> Conservatory Roof -> Orangery -> Swimming Pool -> Banyan Tree (left to right - not easy!) -> The Nightmare Room -> First Landing -> Top Landing -> Master Bedroom and complete the game.
You can't complete it twice though, because the rooms with those enemies in don't become accessible again even after beating the game.

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?

Manic Miner's (maybe) the first to have in-game music on the Spectrum, but obviously there are a fair few arcade games that did it earlier; while I suspect everyone here is aware of that I do see it often claimed as though it's the first game ever to do it on any platform, when it clearly wasn't. Rally X is probably the best example of an arcade game doing it earlier:
I can certainly believe it was the first game on the Spectrum to have in-game music though - it was fairly early on in the Spectrum's lifespan and music in games wasn't as ubiquitous at the time.
The part of the claim I doubt is the "thought to be impossible" part - I'm pretty sure the music in Space Invaders is done exactly the same way as Manic Miner does it, and as much as Matthew Smith did a great job with the game design he wasn't the most amazing programmer in the world, at least not at the age of 17, and plenty of others would surely know it to be possible. I imagine most simply chose a higher framerate over trying to have something somewhat resembling music playing; after all, if you want in-game music you have a tape player attached - just play it yourself.
As for the "plays continuously" comment, I suspect it means as opposed to something like Virtua Racing, where short jingles play at checkpoints but leaves periods without music, or Road Blasters, where the music only comes in towards the end of each level. I doubt it's claiming the air countdown doesn't count and has simply confused the two games.

🙂 
No, because Manic Miner was first by a fair way (a year or just under I think) which discounts the "JSW First" part of it. 🙂
I'm also not convinced at all it was the first game to have an in-game tune that "played continuously" during play either, but I would need to research that to find an 82 or early pre-June*** 83 game that did. It could be the first ZX game to do this but as said I'm not convinced.
*** I'm only about 90% sure on that month, the Software Projects re-release of it was late 83
 
 

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?

If it helps, this is using the original game, not the highscore challenge version; I just put it here since it's highscore-related. Finding the maximum total score (without dying) was an interesting challenge in itself. On top of the "improvements" I shared before (all of which are also in this run) I managed to score 1863 points in The Vat; unfortunately it wasn't feasible to do this and also reach the maximum total score in the same run due to the life count.
 

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.

Andrew Broad made the following comments on the Yahoo! Group when he reviewed JSWED back in November 2005:
No Kamikaze
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An interesting name for what I would term "item-retention" if I could afford a wider window. 😉
"A sadistic game designer", eh? 😆

Bonus Room
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Did I read somewhere that the items in a Bonus Room don't count towards removing Maria? Sacrilege!
It's really cool that the screen colour-cycles when you get an extra life, as in Manic Miner.
Perhaps certain JSW games could give you an extra life after you've collected a certain number of items, or exceeded a certain score (to which points are awarded for collecting items and visiting rooms that you haven't visited before).
There's a bug (or useful quirky feature?) whereby erroneous colour-attributes appear in the playing-area if you acquire too many lives. These colour-attributes behave as Water unless associated with a cell-class (but unlike Custom cells, they don't cause the Cell-Class 1 pixel-pattern to appear).
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There are no other references in the Group posts that would shed any light on the issue in question. However, there was also a comment of yours, Ian, in February 2017:
Re: Patch to reset cells' FLASH-bits
Andrew wrote:
> (I encountered a bug in JSWED when setting "The Off Licence" to be a bonus-room: I ticked "Bonus room" in > "Room properties", but when I checked back there, it was unticked. When I playtested it, it /was/ a > bonus-room: the items gave me extra lives, without colour-cycling.)
I have experienced a similar problem; reopening the Options->Room menu causes the Bonus room box to be unticked (after having ticked it previously).  However, when I playtested it, it wasn't a bonus room (no extra lives and no colour-cycling).
The reason I returned to the Room Options menu was to tick the 'No Kamikaze' option, in order to have both options switched on in the same room.  I thought I would see what would happen if Willy collected all the items in a multi-item room, and then died before leaving the room!  The result: many extra lives, which eventually spilled over beyond the status bar and caused corruption across the range of addresses #58xx-#5Fxx (including the attribute file for the entire screen, the primary and secondary attribute buffers for the playing area and the stack - the latter of which eventually led to a system reset!!)

🙂 
That's quite possible. And John Elliott could actually confirm it if he stumbles upon your comment one day.

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).

It's a good question!
I'll start my reply with the contentious bit ;). I really don't think that it's called the 'Bonus Room', not 'Bonus Cavern', feature because it was designed with JSW-style gameplay in mind. I know you always make a point about the distinction between rooms and caverns, but I don't think it's universally accepted or applied. 'Room' is the most generic word for a screen in the game and I'm pretty sure that's why the feature is called the 'Bonus Room', without any deeper meaning to it.
Moreover, the distinction between JSW-style and MM-style games (and also rooms) is blurred in JSW64. You can have a room with a portal which is the only way out, but you can also have a room with a portal that simply acts as a teleporter, because you can also exit this room through one or more "JSW-style" exits. JSW64 is a "place" where the distinction between rooms and caverns as per your definition is particularly vague.
Anyway, I've carried out some testing in response to your query and the result is that there is an easy - although admittedly imperfect - solution to the problem you've envisaged. It's keeping the "No Kamikaze" option deactivated.
Let's start from the basics for anyone interested. Both the "Bonus room" option and the "No Kamikaze" option can be activated or deactivated (ticked or unticked) in the following way: right-click "Rooms" (a menu appears), go to "Room options" (JSWED's manual mistakenly calls it "the Room properties screen" - this should be corrected as it's confusing) - another menu appears - go to "General", there they are.
With the "No Kamikaze" option ticked, the game plays in the room in question as in MM, i.e. if you die after collecting an item, when you respawn, the item (or items) you collected before dying are restored and your item count is adjusted to what it was before collecting them. If you collect more than one item in such a room and then lose a life, you will have a net gain of at least one life (more if you have collected more items) and so there is a clear and present danger that the extra lives you keep gaining in such rooms (if there are many of them) could start to spill over beyond the bottom of the status bar.
The easy solution to this is to have the "No Kamikaze" option deactivated. With this, the game plays as in JSW, so after you have collected an item, it's not there any more also after you lose a life. However, this doesn't affect the ability to leave the room via the portal - you collect an item, you die, the item is not there any more, but once you have collected all the other items in the room, the portal starts flashing. The program remembers that an item has been collected.
I know, it eliminates the challenge of having to collect all the items in the room without losing a life. Oh well...

I fully agree with all of your comments, Ian 🙂 .

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.)

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.)

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.

In view of lack of any further feedback that would contradict what has been established so far, I published the videos of walkthroughs of the four versions of "Terry The Turtle" on the JSW Central YouTube channel. Here they are:
Yellow (Normal)
Cyan (Intermediate)
Red (Hard)
Vektor (Special Edition)
There is one correction I need to add, though, to what I wrote before. There is one uncollectable item in the Yellow and Cyan versions that I failed to mention. It's in the room "Shell Shock!" (023). I am pretty sure it cannot be collected, because, first, there is no way to get where it is to grab it, and, more importantly, the player gets trapped in that section of the map, so even if they could reach it and collect the item, they would have to desist from it in order not to get trapped.
So my final verdict on the collectability of the items in "Terry The Turtle" is as follows:
Yellow version: It is possible to collect 93 out of 157 items. 89 items can be collected without loss of life. Four more can be collected if you deliberately sacrifice one life in the room "U-852 Secret Load & Kill Screen" (124). The uncollectable items are: the uppermost item in "Hidden Chamber" (012), the item in "Shell Shock!" (023) and 62 items in "U-852 Secret Load & Kill Screen" (124) (including 13 items in the enclosure at the upper left and 49 items in the central part of the room).
Cyan version: It is possible to collect 61 out of 73 items, all of them without loss of life. The uncollectable items are: the uppermost item in "Hidden Chamber" (012), the item in "Shell Shock!" (023) and 10 items in the enclosure at the upper left in "U-852 Secret Load & Kill Screen" (124).
Red version: It is possible to collect all 48 items, without loss of life. This is the only version that is item-completable.
Vektor version: It is possible to collect 72 out of 135 items (even though the message on the status bar suggests there are 68 items to collect). In fact, 68 items can be collected without loss of life. Four more can be collected if you deliberately sacrifice one life in the room "U-852 Secret Load & Kill Screen" (124). The uncollectable items are: one item (either one) in the room "STYX - THE RIVER OF HATE" (068) (when the player falls down from "DESCENTION" [069], they can collect either one or the other item; later on, there is no way to go back and fall down again in order to collect the other item) and 62 items in "U-852 Secret Load & Kill Screen" (124) (including 13 items in the enclosure at the upper left and 49 items in the central part of the room).