PLAN.md

Blame: the commit that last changed each line · file · history

`e3bfc714` 2026-10-10 Pavel Safronov	1	# Plan
	2
	3	What is left to do on Nordic Skating, in the order it is meant to be picked up, with what
	4	has been decided about each item and what is still open. The README says what the app
	5	does today; this says what it does not do yet.
	6
	7	Last brought up to date 2026-10-09.
	8
	9	## Where things stand
	10
`2f7e86b7` 2026-10-10 Pavel Safronov	11	Built: the endless lake, autopilot and steering, the synthesized sound, ice whose
	12	thickness can be seen and heard, forks, narrow passes and open sea, the sound button,
	13	the About box and the link to the source. Falling through is written and switched off.
`e3bfc714` 2026-10-10 Pavel Safronov	14
	15	Postponed until the items below are ironed out: game controller, then
	16	multiplayer (the last step of the original six).
	17
	18	## Next
	19
`2f7e86b7` 2026-10-10 Pavel Safronov	20	### 1. Motion — built, waiting to be felt
	21
	22	The problem was that each stride swung the view from side to side and tilted it, the
	23	speed never changed, and steering slid the skater sideways at a fixed rate.
	24
	25	What was built (2026-10-09), all four changes proposed:
	26
	27	1. A speed that breathes with the stride. A push adds about 1 m/s over half a
	28	second; drag takes it back through the glide. Around 7 m/s.
	29	2. Steering that turns the skater. The skater has a place, a direction and a speed.
	30	Input sets how fast the direction changes, up to a 16 m circle, with a third of a
	31	second to lean into it. Paths are arcs by construction.
	32	3. An autopilot that carves. It aims 18 m ahead on a line that wanders up to 6 m
	33	either side of the middle, and steers with the same limits as a person.
	34	4. A head that stays level. The side-to-side sway and tilt are gone. What is left is
	35	a 3 cm rise on each push and a lean into real turns of at most 3.5°.
	36
`c2835cab` 2026-10-10 Pavel Safronov	37	Changed on Pavel's report (2026-10-10): the autopilot fought the skater. It had a
	38	line fixed in advance, and after any steering it went back to it: steer left out of a
	39	right-hand curve, let go, and it turned right again. Now the line is a plan that
	40	steering rewrites. Let go, and the line is centred where the skater has got to and its
	41	next swing begins the way they are going. Nothing eases back to the middle any more,
	42	and where the skater is, not the fork's preference, decides a fork for a skater who
	43	does not steer at it.
	44
`2f7e86b7` 2026-10-10 Pavel Safronov	45	Decided by Pavel.
	46	- The whole lake is safe: falling is suspended, and thickness decides only the sound.
	47	- Impossible ice is allowed: thinner than could hold anyone, down to 8 mm, never cracks.
	48	- More complex paths are wanted later, so nothing here may rule them out.
	49
	50	Kept open on purpose. The skater is a point with a direction on a flat sheet, not an
	51	offset along a one-way line, so turning round is already something the model can do.
	52	One rule stops it: the skater may point at most 50° off the line of the channel
	53	(`MAX_HEADING` in `src/skater.ts`). What would still need doing for a skater going
	54	backwards: forks are entered by passing a distance and are not left by passing back
	55	over it, and only 100 m of shore is kept behind the skater.
	56
	57	Still to judge, by feel.
	58	- Are the push and the glide strong enough to notice, or too strong?
	59	- Is the carving too wide, too tight, or about right? Should it stop in a narrow pass?
	60	- Is the turning limit right for a finger on a phone?
	61	- Should the stride length follow the speed, or thin ice or a pass slow the skater?
	62
	63	### 2. Screen wake lock — built
	64
	65	Asked for when the page opens, each time it comes back from being hidden, and at the
	66	first touch, since some browsers give it only then. Where the browser has no such thing
	67	it is silently skipped. Not checked on a phone: leave it on autopilot and see whether
	68	the screen stays on.
	69
	70	### 2a. Settings, times of day, and a different lake every visit — built
	71
	72	Asked for by Pavel on 2026-10-09, with the reason: one of the main things about this is
	73	to be reloading the page and finding yourself somewhere slightly different.
	74
	75	What was built.
	76	- A settings box, opened from the top left, at the foot of the screen so that what
	77	it changes can be seen changing behind it. It is the control panel new options go in.
	78	- Impossible ice is a setting, off by default.
	79	- Four times of day: day, dusk, night under the Milky Way, and the aurora. The
	80	setting starts on "Surprise me", which is whichever the lake comes with.
	81	- Every visit is another lake: a number from 1 to 999,999 picked on opening, which
	82	decides the water, the ice, the trees and the time of day. `?seed=` asks for one by
	83	number, so a lake can still be come back to, linked to, photographed, and, later,
	84	shared between players.
	85	- Randomize, a button beside Settings (and the R key): another lake at once,
	86	without a reload, and put in the browser's history so that Back returns to the lake
	87	left. A reload still gets a new lake; which lake a page shows is kept with its place
	88	in the history, not in the address.
	89	- The Source link left the top bar to make room; it is in the About box.
	90
	91	Still to judge.
	92	- Are the Milky Way and the aurora right? The aurora moves, slowly; a still picture
	93	cannot show whether it moves well.
	94	- Is night too dark to read the ice by, on a phone outdoors?
	95	- Is "slightly different" different enough? Only the lake and the time vary now.
	96
	97	Ideas for more variety between lakes, none started: a moon and its phase, falling
	98	snow, mist that thins and thickens, wind in the sound, dawn, how wooded the banks are,
	99	how hilly, the colour of the aurora, how fast it moves.
	100
	101	Ideas for more settings, none started: speed, how far the autopilot carves, how long
	102	the strides are, how much the ice cracks, falling through, the haze.
`e3bfc714` 2026-10-10 Pavel Safronov	103
`0045befd` 2026-10-10 Pavel Safronov	104	### 2b. More in the scene — partly built
	105
	106	Pavel, 2026-10-10: more details in the scene are welcome, and named these.
	107
	108	Built, waiting to be looked at.
	109	- In the sky: shooting stars at night; a comet over one night lake in three; an
	110	aeroplane and its trail over two day or dusk lakes in three.
	111	- Weather: clear, snow, or a blizzard, as a setting that starts on "Surprise me".
	112	Falling snow that streams past the skater, wind from a direction of the lake's own,
	113	the wind's sound, cloud over the sky, and less distance to see through.
	114
	115	Still to judge. Is a blizzard thick enough, and is 200 m too little to see by? Is
	116	the wind too loud over the ice? Are shooting stars too frequent? The aeroplane is
	117	silent; should it be?
	118
`b2c4db9f` 2026-10-10 Pavel Safronov	119	Built since, waiting to be looked at (2026-10-10).
	120	- Cracks made by the skater, and skate tracks. The marks are drawn on a picture of
	121	the hundred metres square of ice round the skater. Tracks and the scratch of each
	122	push are always left; cracks are drawn where they are heard, and a push on cracking
	123	ice starts more. Seen working as a drawing; the cracks have not been seen in the app
	124	itself, only the tracks.
	125	- A long island in the middle of the lake: see "Channels that part and join again".
	126
`94b3b29f` 2026-10-10 Pavel Safronov	127	Improved on Pavel's look at them (2026-10-10), waiting to be looked at again.
	128	- The cracks the skater makes were too thick and pixelated. They were drawn into a
	129	picture with ten pixels to the metre. They are now lines of their own, a pixel wide at
	130	any distance, and a crack runs out from its middle at 28 m/s instead of appearing whole.
	131	Tracks and push scratches are drawn the same way.
	132	- The cracks the ice already has were not realistic: thirty jagged lines at random.
	133	They are now a network made the way ice cracks: a few long, nearly straight runs, and
	134	later cracks that leave an earlier one at a wide angle and stop at the next.
	135	- Still not done: the picture of the ice's own cracks repeats every 32 m, and they are
	136	painted, so close to they are softer than the hairlines the skater makes.
`c2835cab` 2026-10-10 Pavel Safronov	137
`b2c4db9f` 2026-10-10 Pavel Safronov	138	Still to judge. Are the tracks too faint against the ice's own cracks, which are the
`c2835cab` 2026-10-10 Pavel Safronov	139	same colour? Should they fade with time?
`b2c4db9f` 2026-10-10 Pavel Safronov	140
`893cda77` 2026-10-10 Pavel Safronov	141	- Snow drifts (2026-10-10): snow lying on the ice in streaks down the lake's wind,
	142	under falling snow and more in a blizzard. A drift slows the skater to about half
	143	speed and takes the ring out of the ice: the "bad ice" of the first description of
	144	this app. Still to judge: is half speed too much of a penalty for a relaxing skate,
	145	and are there too many drifts in a blizzard to find a way between?
`0045befd` 2026-10-10 Pavel Safronov	146
	147	Further ideas, none started: a moon and its phase; mist that thins and thickens;
	148	dawn; how wooded and how hilly the banks are; the colour of the aurora; birds; a far
	149	shore with the lights of a house at night; satellites; a bare rock, as in the film.
	150
`b2c4db9f` 2026-10-10 Pavel Safronov	151	### Channels that part and join again — built, waiting to be tried
`0045befd` 2026-10-10 Pavel Safronov	152
	153	Pavel's question: is this something like a long island of grass in the middle of a
`b2c4db9f` 2026-10-10 Pavel Safronov	154	lake or river? Yes, and that is what was built (2026-10-10): a low bank of reeds
	155	180 to 480 m long, in the middle of a channel, with water both sides that is one water
	156	again beyond it.
	157
	158	It turned out simpler than a fork whose channels rejoin. The island is a thing standing
	159	in one channel, like an islet but long: the channel is made wider by the island's width
	160	where it stands, and the skater has the water on whichever side of it they are on. No
	161	channel is left or joined.
	162
	163	Still to judge. Is one every 5 km right? Do the reeds read as an island from a
	164	distance, or as a smudge? Should some islands be wooded, like the ones at forks?
`0045befd` 2026-10-10 Pavel Safronov	165
`3f3d6bce` 2026-10-11 Pavel Safronov	166	### 2c. Pace — built, waiting to be felt
	167
	168	Asked for by Pavel on 2026-10-10: a peaceful meander, something faster, and something
	169	ridiculously fast, as if training for the Olympics, with whatever between makes sense.
	170
	171	What was built. Five paces: Meander (13 km/h), Cruise (25, as it was), Brisk (36),
	172	Racing (45) and Olympic (54). A button at the bottom right steps through them; so do
	173	the up and down keys and a controller; and they are in Settings. Strides shorten and
	174	quicken with pace, the skater crouches, the view widens, the air rushes, the turning
	175	circle grows, and the autopilot looks and steers further ahead.
	176
	177	Still to judge.
	178	- The names, which Pavel was not sure of.
	179	- Is Olympic fast enough to be ridiculous? It is a real speed skater's pace. There is
	180	room above it, though the lake's bends and narrows were made for 25 km/h.
	181	- At a racing pace a skater is kept well back from the shores, so in ordinary water
	182	there is not much steering to be done. Too restrictive?
	183	- Should a pass, a fork or a bed of islets slow a racer down?
	184	- Does the wider view at speed feel fast, or only odd?
	185
`8b498d51` 2026-10-10 Pavel Safronov	186	### 3. Installable app — built, not yet tried on a phone
`e3bfc714` 2026-10-10 Pavel Safronov	187
`8b498d51` 2026-10-10 Pavel Safronov	188	A web manifest and a service worker, made by `vite-plugin-pwa`. Installed, the app has
	189	its own icon, opens full screen with no browser bars, and works with no network: the
	190	whole of it is kept on the phone, and nothing is fetched after that. A new version is
	191	taken up the next time it is opened.
`e3bfc714` 2026-10-10 Pavel Safronov	192
`8b498d51` 2026-10-10 Pavel Safronov	193	Checked in a desktop browser: with the network off and the server stopped, the app
	194	opens, opens a lake by number, and Randomize works. Not checked: installing it on a
	195	phone, on either Android or an iPhone.
	196
`3f3d6bce` 2026-10-11 Pavel Safronov	197	The icons are supplied by Pavel: a skate for the app and the pace button, and a
	198	speaker and a crossed-out speaker for the sound button, all by Icongeek26, from
	199	Flaticon, credited in the About box and the README as the licence requires. The Tilt
	200	button has a phone in a hand for on and a phone by itself for off, also supplied by
	201	Pavel; to confirm: whether those two are by Icongeek26 as well. The artwork is
`8b498d51` 2026-10-10 Pavel Safronov	202	`assets/skate-shoes.png`, and `npm run icons` makes the home-screen and tab icons from
	203	it, pale on the colour of black ice.
	204
	205	Open. It opens in whichever orientation the phone is held. Should it lock to one?
`e3bfc714` 2026-10-10 Pavel Safronov	206
`df2b8215` 2026-10-10 Pavel Safronov	207	### 4. Islets to skate round, and turning right round — built, waiting to be tried
`e3bfc714` 2026-10-10 Pavel Safronov	208
	209	Pavel's idea. In the film the skater does a loop around a patch of grass and then
`df2b8215` 2026-10-10 Pavel Safronov	210	carries on. Add that, as a kind of fork or obstacle. More complex paths are welcome.
	211
	212	What the film shows (looked at 2026-10-09): from 2:12 to 2:35, a skater weaving
	213	among small tufted islets of reeds standing in the ice, several to a cluster. Also a
	214	bare rock in the lake at 1:52, and at 0:35 ice covered in looping white skate tracks.
	215	And at 1:17 the ice is measured on camera: 45 mm. The sound alone gives 41 mm.
	216
	217	What was built.
	218	- Islets: reeds on humps of frozen ground, 5 to 15 m across, in beds. The autopilot
	219	steers round them; a skater steering at one is turned aside at the last moment, and
	220	nobody can get onto one.
	221	- Turning right round. The limit on how far off the lake's line the skater could
	222	point is gone from open water. Held over, the skater circles, 16 m in radius, and can
	223	skate back up the lake; let go and the autopilot turns them down it again. The land,
	224	the ice's thickness and the view all follow whichever way the skater faces.
	225	- A touch chooses at a fork. With steering now turning, holding it over until the
	226	fork would be a circle, so a touch one way within 200 m of a fork is taken as asking
	227	for that side.
	228
	229	Still to judge, by feel.
	230	- Is circling an islet with a finger possible, and pleasant? The circle is 16 m in
	231	radius whatever the islet's size.
	232	- Is it too easy to turn round by accident? Holding a steer for seven seconds does it.
	233	- Are there too many islets, or too few? Do the reeds look like reeds?
	234
	235	Not done, and wanted or possible.
`0045befd` 2026-10-10 Pavel Safronov	236	- Forks of three. Channels that part and join again: see the section of that name.
`df2b8215` 2026-10-10 Pavel Safronov	237	- A bare rock, as in the film. A drawing of the skater's own tracks on the ice, as in
	238	the film: with loops now possible, they would show them.
	239	- Forks cannot be gone back through: a skater who turns back above a fork stays in the
	240	channel they chose, which is the right water but would matter if tracks were drawn.
`e3bfc714` 2026-10-10 Pavel Safronov	241
`8b498d51` 2026-10-10 Pavel Safronov	242	### 5. Check the chirps against the film — tried, and the film cannot say
`e3bfc714` 2026-10-10 Pavel Safronov	243
	244	Pavel's request. The falling "pew" of a distant crack is the one part of the sound
`8b498d51` 2026-10-10 Pavel Safronov	245	that comes from the model alone.
	246
	247	What was tried (2026-10-09), three ways, the last kept in `tools/analyse-video.mjs`:
	248	1. Follow the loudest frequency down after each burst and fit it: 3 of 124 fitted.
	249	2. Split each burst into bands from 1 to 7 kHz and time each band's arrival, to test
	250	the one thing about a chirp that does not depend on where the crack was: that
	251	arrival times fall as frequency to the power -0.6. 3 of 203 bursts had any spread.
	252	3. The same in the band just above the note, where the chirps' sound is: 3 of 122, and
	253	those three disagree with each other.
	254
	255	Finding. In nearly every burst every band arrives within 30 ms of every other. The
	256	likely reason is that the microphones were close to the skater: a sound from close by
	257	has had no distance to spread out over. The film gives the note (740 Hz, so 4.1 cm) and
	258	not the chirp. Not looked at: the reassigned spectrogram, which sharpens a ridge but
	259	cannot put spread into a sound that has none.
	260
	261	What would settle it, if it matters: a recording made some hundreds of metres from
	262	the cracks, with the ice's thickness known. The paper's own data are of that kind.
`e3bfc714` 2026-10-10 Pavel Safronov	263
`9f2e2509` 2026-10-10 Pavel Safronov	264	### 5a. Tilt to steer — built, not tried on a phone
	265
	266	Asked for by Pavel on 2026-10-10. A setting, off by default, shown only on phones and
	267	tablets: lean the phone like a wheel to steer, level to let the skater skate itself.
	268	Dragging still works with it on.
	269
`fe6b506c` 2026-10-10 Pavel Safronov	270	Tried by Pavel on a phone, 2026-10-10: it works. Turning it on in Settings was
`df03cd8b` 2026-10-10 Pavel Safronov	271	cumbersome, so there is now a Tilt button at the bottom left of the screen, hidden
	272	where there is nothing to tilt, and the setting is gone. Tilt, the rotation lock and
	273	full screen in a browser tab all confirmed working by Pavel on a phone.
`fe6b506c` 2026-10-10 Pavel Safronov	274
	275	Also asked for: the screen should not turn with the phone while tilt is on. Built with
	276	the browser's own rotation lock, which Android gives to an installed app or a page in
	277	full screen (so a tab goes full screen while tilt is on) and an iPhone does not give to
	278	a web page at all. Not tried on a phone.
	279
`9f2e2509` 2026-10-10 Pavel Safronov	280	Checked in a desktop browser pretending to be a phone, with made-up tilt: the setting
	281	shows, is remembered, and leaning turns the skater. Not checked: a real phone, where
	282	the things to judge are whether 4° of rest and 28° for full steering are right, whether
	283	leaning is the right way round in each orientation, and whether an iPhone's request for
	284	leave appears and works. It needs HTTPS, so it can only be tried on the live site.
	285
	286	Open. There is no way to set which lean counts as level: it is level. Someone lying
	287	on their side cannot use it.
	288
`e3bfc714` 2026-10-10 Pavel Safronov	289	### 6. Phone controls
	290
	291	Waiting on Pavel, who is still trying the touch steering and will send feedback.
	292	Nothing to do until then. Steering and choosing a fork have only been checked with the
	293	keyboard, never with a finger. Item 1 will change how steering feels, so feedback given
	294	before it lands may need giving again.
	295
	296	## Later
	297
	298	### Competitive mode
	299
`2f7e86b7` 2026-10-10 Pavel Safronov	300	Decided: low stakes for now. The aim at present is something fun and relaxing: nobody
	301	falls through and nothing is scored. Falling is written and switched off (`RULES` in
	302	`src/skater.ts`), and would be part of this mode. A competitive mode for people who want
`e3bfc714` 2026-10-10 Pavel Safronov	303	one is a maybe, as an option beside the relaxed one and never instead of it. Ideas: time
	304	spent on singing ice, distance without falling, a set course against the clock.
	305
`94b3b29f` 2026-10-10 Pavel Safronov	306	### A figure, and a view from behind them
	307
	308	Asked about by Pavel on 2026-10-10: what would it take to add a figure and make this a
`da5f527b` 2026-10-10 Pavel Safronov	309	third-person game? Not started, and not decided: Pavel is thinking it over. In short: the lake needs nothing, the skater already
`94b3b29f` 2026-10-10 Pavel Safronov	310	knows everything a figure would act out, and the work is the figure itself.
	311
	312	What is there already. The skater has a place, a direction, a speed, a rate of turn,
	313	and a stride with the moment of each push in it (`src/skater.ts`): everything a figure's
	314	pose is made from. The world is drawn round the skater and would be drawn round a camera
	315	a few metres behind them without change.
	316
	317	What it needs.
	318	1. A camera that follows: some metres behind and above, easing after the skater
	319	rather than bolted to them, and kept out of the banks, trees and islets, which in a
	320	pass 5 m to a side is most of the problem. And a way to choose the view.
	321	2. The figure. There are no models in this project and no way of loading any. Either
	322	one is made here of simple shapes, in keeping with trees that are cones, and moved by
	323	rule from the stride (push leg out and back, the other gliding, arms swinging, a lean
	324	into turns); or a made model with made animations is brought in, which means a loader,
	325	a megabyte or more to download and keep offline, a licence to honour, and finding a
	326	skating animation, which are rare. The first is the recommendation.
	327	3. What a figure shows up. A shadow under it, or it floats. Tracks from each skate in
	328	turn, not one line down the middle. Something to see it by at night. A faint
	329	reflection in black ice would be cheap and would look like the film.
	330
	331	The risk is the figure's movement: an awkward skater is worse than none. The view
	332	from the eyes should stay, as a choice.
	333
	334	It is also most of multiplayer. Other players have to be drawn as something, and
	335	this is the something.
	336
`da5f527b` 2026-10-10 Pavel Safronov	337	How it would be done, if it is: in four passes, each something to look at.
	338	1. The camera that follows, a stand-in shape for the figure, and the choice of view.
	339	2. The figure, and its stride.
	340	3. Its shadow, its reflection, and tracks from each skate.
	341	4. Tuning, which for the figure's movement will take some going back and forth.
	342
	343	About as much work as the long islands and the tracks on the ice together.
	344
	345	To decide first.
	346	- Made here of simple shapes (recommended), or a model brought in?
	347	- Which view the app opens in, and how the other is chosen: a button, a setting, both?
	348	- One figure, or a choice of them, which multiplayer would want anyway?
	349
`893cda77` 2026-10-10 Pavel Safronov	350	### Game controller — built, not tried with one
`e3bfc714` 2026-10-10 Pavel Safronov	351
`893cda77` 2026-10-10 Pavel Safronov	352	Either stick or the direction buttons steer; Y or triangle goes to another lake; X or
	353	square turns the sound on and off (2026-10-10). The stick's mapping is tested; no
	354	controller has been connected to it. To judge with one in hand: the 15% rest in the
	355	middle of the stick, and whether the buttons are the right ones.
`e3bfc714` 2026-10-10 Pavel Safronov	356
	357	### Multiplayer
	358
	359	Postponed. The lake is the same for everyone given the same seed, so players need only
	360	share a seed and send each other where they are. `~/code/touch` and
	361	`~/code/cat-playground` do this peer to peer with peerjs, with no server.
	362
	363	## Settled
	364
	365	Raised, answered, and needing nothing more.
	366
	367	\| Item \| Outcome \|
	368	\|---\|---\|
	369	\| Repository was private, so the in-app links led to a sign-in page \| Made public by Pavel, 2026-10-09 \|
	370	\| No licence \| MIT, in `LICENSE` \|
	371	\| The credit for the paper the sound's physics is from was partly from memory \| Checked against the journal's page on 2026-10-09: authors, title, volume, pages, DOI and CC BY 4.0 licence are all as the README has them \|
	372	\| Forks are two-way, not "multiple" \| Fine as they are for now; more complex forks are part of item 4 \|
	373	\| Thick ice does not sound "bad"; the bad ice is the thin end \| Fine as it is \|
	374	\| Frame rate on a phone, including at sea \| Good, by Pavel's testing \|
`2f7e86b7` 2026-10-10 Pavel Safronov	375	\| Falling through has no cost and nothing is scored \| Falling is switched off altogether for now (2026-10-09); see Competitive mode \|
	376	\| Only the middle 3 m of a channel was guaranteed sound ice, and the autopilot was to wander \| Gone with falling: the strip of sound ice was removed. Turning falling back on needs a safe line for the autopilot first \|