DigitalDuck

Making something run more efficiently doesn't have to mean speeding it up - it can be used to make the game run at a smooth speed (syncing to display refresh and counting frames) instead of speeding up when there are less enemies and slowing down when there are more, or add other more complex elements to the game. Personally I think somewhere between original Manic Miner's Central Cavern with music off (about 12fps) and the GBA version (20fps) is a good speed, which is why I set the default speed to 15fps in Redux.

Just for fun: if you collect the bottom item in Skylab Landing Bay while you're on 33 lives and *99xx points, you're killed by the extra life you're awarded for collecting the item. MM-extralife_VP8.webm

With the life sprite in its first position, you can also get through the corner of the new platform and land on the small platform underneath it. This jump stops being possible at 37 lives.

So I have a couple of corrections to this, namely that I'd missed some things that reduce the life count before some levels become incompletable: Eugene's Lair - at 39 lives, the platform with the black toilet is completely overshadowed by the garbage platform. Unfortunately it's now one cell too high to safely drop down from, and there's no other way down without falling too far. Return of the Alien Kong Beast - at 37 lives, all ways back down are blocked, and again the only way to get down is to fall too far. Attack of the Mutant Telephones - while it's possible to go from top to bottom by jumping through the top of the screen, the platform in the middle becomes an island once you reach 42 lives and there's no way to get up or down from it. Interesting. I'll post about it in that thread if I decide to experiment with that, but it's definitely unique for JSW-style games.

Yes, it's both the playing area and the buffer that's overwritten. When drawing a sprite it adds 256 to the memory address to go to the next pixel row, but naturally the screen attributes follow directly after the screen pixels so they're being drawn to. Even in the most extreme scenario lives are only drawn to pages 80-95 (memory addresses 0x5000 to 0x5FFF) which contain the lower third pixel data for the screen, attribute data for the screen, and the attribute buffers. I'm not sure where the stack is stored, but I don't think it's being overwritten here.

Absolutely - unfortunately this scenario doesn't seem to exist in the vanilla game, but with the right sprites and colours you could have a situation where it cycles between floor, wall, air, and nasty (or the four elements, water, earth, air, and fire), and require the Willy life sprite to be in a certain state to make the level passable (perhaps even requiring floor at some points, air at others, and wall at yet others, so you have to "edit" the level as you play).

Not shown in the video because I just wanted to get something out there quickly, but what's actually drawn on the screen depends on the sprite shown for Willy's lives; as I have the music turned off, it's not cycling. The state I have the sprites paused in is the only state in which items are auto-collected. In all cases at least one of the two blocks drawn is a floor block. I suspect the black cells are actually air tiles, hence the item being collectable; these same black tiles are nasties in Skylab Landing Bay. I actually discovered this a while ago with lives POKEs, this was just my first time seeing if it can occur during normal gameplay. You can experiment yourself with POKE 33879,n. After 48 lives, they start being drawn over the level name and air counter instead. There's a limit to how many lives you can have before each level becomes incompletable (although you can always lose lives until they become completable again). I've split them into three groups: Early blockers: Central Cavern - at 39 lives, you cannot jump over the robot without landing on the extended platform, which blocks your fall to below. Interestingly, it becomes possible again at exactly 46 lives only, as this allows you to walk to the right and drop down that way (similar to what the GBA/PC version allows you to do), but at 47 lives that way becomes impassable too. Miner Willy meets the Kong Beast - at 40 lives, there is no way of getting through the opening after pressing the switch to collect the last banana. Endorian Forest - at 40 lives, the middle trunk and extended platform seal you in the starting section. Return of the Alien Kong Beast - 40 lives, same as Miner Willy meets the Kong Beast. Skylab Landing Bay - at 34 lives, the nasties block a mandatory path. The Final Barrier - at 46 lives, there is no way of getting out of the top-right area after collecting the keys there. Standard blockers: At 47 lives, the "platform" extends covering the entire play area (minus the last two cells, but one of those is always a wall, and Willy can't fit through a gap of one cell). For The Cold Room, The Menagerie, Eugene's Lair, Processing Plant, and The Warehouse, 47 lives is the point at which they can no longer be completed as the entire screen is blocked and cannot be traversed from top to bottom. No blockers: These come in two forms: in Abandoned Uranium Workings, Wacky Amoebatrons, The Bank, The Sixteenth Cavern, Amoebatron's Revenge, and Solar Power Generator, you start in the bottom half of the screen and exit at the top. As a result, platforms stretching across the screen don't inhibit progress at all. You do normally need to revisit the bottom half of the screen in Solar Power Generator, but the platform extends to make that unnecessary long before it's made impossible. The second form is in The Vat, Attack of the Mutant Telephones, and Ore Refinery. While all three of these levels require going from top to bottom to top (or bottom to top to bottom in the case of Ore Refinery), they also have platforms very near to the top of the screen, requiring wall tiles to prevent you from jumping outside of the screen boundaries. These wall tiles are replaced with floor tiles, allowing you to jump through the screen vertically and access the other half of the screen. All of these levels can be completed regardless of the number of lives you have. Whether it should be allowed or not is already contentious enough with what I've already shown - I think we can safely say that if cheats are required then it definitely shouldn't count, so anything with extensive corruption is out. I believe this also means that the maximum attainable life count in the game is 38 (Skylabs limiting to 34 plus four extra lives attainable in one loop).

It seems that it's still collectable when another attribute is printed over an item - this happens in Abandoned Uranium Workings. It also seems that the bug is consistent in what it puts on-screen. My main concern is that it isn't possible the first eight (at minimum) times you complete the cavern, and these are clearly different caverns to those intended due to modified terrain.

I played through, albeit not in real-time (so savestates, rollback etc.) - I'm doing it for a max score run because I think it's interesting to watch the game disintegrate as you play. It takes about two hours of perfect play to get to this point so I don't recommend it.

In short: earning enough extra lives corrupts the screen, which acts as floor tiles in most caverns and allow routes that aren't normally available. The following five scores are shown in the video: Abandoned Uranium Workings - 1856 Miner Willy meets the Kong Beast - 4142 Wacky Amoebatrons - 1377 Attack of the Mutant Telephones - 1750 Ore Refinery - 1884

It doesn't use any POKEs, it's possible in both the original Bug-Byte and Software Projects versions without any modifications. However, it's not possible in the high score challenge version of the game.

I've managed to complete Abandoned Uranium Workings with 1856 points, but it's in a very non-standard way and probably shouldn't count in the rankings... I'll reveal more when I'm done exploring other levels.

Sounds like a great idea for another game...

This is the definition I was thinking of - although levels needn't specifically be completed in a linear order (for example, most Mario games have a fairly open structure where you choose a level, and completing that level grants access to additional levels) they are self-contained challenges which have a clear definition of "completion". In the case of Manic Miner, completing a cavern gives you a score bonus based on how quickly you completed the room and then loads the next cavern, refreshing your air and providing a new checkpoint to return to when you die. So each cavern definitely counts as a level. This is an interesting one. I'd definitely say 10 levels and 20 rooms, but I'm not sure if I'd count it as 20, 10, or even 0 caverns (the last being the same way I wouldn't consider the whole of Jet Set Willy as one cavern). The C16 version of Jet Set Willy II is split into four parts this way as well - although you can load each part at any time and there's no requirement to complete them (in fact I'm not even sure it's possible to complete most of them). Personally I'd refer to these as levels as well, as they're effectively just larger versions of the Double Miner case, but it would be interesting to know how this was referred to in the manual. The SAM Coupe version of Manic Miner has three sets of caverns, and the title screen asks you to select a "game"... I'm thinking Deserted Isle is a cavern after all.

For me the difference is that in Manic Miner, you're not free to exit at any time - you must collect all items and then head to the portal, and after heading to the portal you can't return (unless you complete a full loop of the game). In Jet Set Willy, you can (almost) always exit a room without collecting any items, and return later should you wish to. I could define a "room" as one screen of the game, such that both Solar Power Generator and Emergency Generator are rooms; but to make a distinction, Solar Power Generator can also be considered a "level", whereas nobody would consider Emergency Generator as a level, for the reasons above. In that sense, a cavern is a room that is also a level. ... is Deserted Isle a cavern?