L-system tree · mimo-v2.6-pro

Let me build this. First check the working directory and p5.min.js.

Plan: L-system tree with axiom "F", rules F -> "FF+[+F-F-F]-[-F+F+F]" or simpler. Generation 1-5. Bound expansion — maybe cap string length. Draw progressively: interpret the expanded string, build a list of segments with parent index and depth, then reveal segments over time in order of distance from trunk (or just in order of string traversal which roughly grows from trunk outward). Better: compute each segment's "birth time" based on distance from root (graph distance), so growth progresses from trunk toward tips.

Wind sway: apply rotation at each branch point based on depth and time — i.e., recursively draw with a sway angle offset that accumulates down the tree. Easiest: build a tree structure of nodes (position, angle, length, depth, parent) and draw recursively with accumulated sway = sin(time*freq + depth*phase + random seed) * amplitude * depth factor. Child branches stay attached because we draw recursively from parent's end point with parent's angle + branch angle + sway.

Implementation: build segments during turtle interpretation into a tree: each segment has parent segment ref, x,y start (computed at draw time), angle (local turn relative to parent), length, depth. Actually store: for each segment: parentIndex, localAngle (relative to parent's absolute angle), length, depth. Then draw recursively computing absolute angle = parentAbsAngle + localAngle + sway(depth, time).

Sway: sway angle added at each node = windStrength * sin(t*speed + depth*0.6 + seed) * (depth factor). Since children are drawn from parent's end position with parent's absolute angle, they stay attached.

Progressive growth: each segment has a growth order = depth in tree (or distance from root along segments). Use totalLength accumulation: order = cumulative length from root. Growth time t maps to revealed length. Segment drawn with partial length if it's the frontier segment. That gives nice progressive growth from trunk to tips.

Leaves: at segments with no children (tips), draw a leaf/flower, appearing when growth passes.

Generation control 1..5 (slider or buttons), Regrow button. Regrow restarts growth (with same grammar), maybe randomize seed for wind variation but same grammar. "Changing generation or pressing Regrow restarts growth using the same chosen grammar."

Bound grammar expansion: rules that expand can blow up; e.g. F -> FF+... with generation 5 gives huge strings. Choose rule like F -> "F[-F]F[+F]F" (3^n growth) — gen 5 = 3^5... Let's compute: axiom F, each F -> F[-F]F[+F]F gives length growth ~5x per gen (F count 3^n... actually F count: n0=1, n_{k+1}=3 n_k + 2*? Let's just cap string length, e.g. max 20000 chars, and cap number of segments. Also keep tree visible at all generations: scale the tree to fit canvas based on bounding box after computing positions (without sway), or scale by generation factor. Best: compute layout once (no sway) to get bounding box, then compute a scale and translate to fit canvas with margin. That guarantees whole tree visible at all generations.

But with sway, tree may exceed slightly — add margin.

Let me pick grammar: axiom "X", rules: X -> F[+X][-X]FX, F -> FF. That's a classic tree. Or the "seaweed". Let's use:
axiom: "F"
rules: F → "FF-[-F+F+F]+[+F-F-F]" — this is a nice symmetric tree (from Wikipedia's L-system tree). Angle 22.5°. Growth per generation: F count 6^n? F -> FF + 2 F's inside = 4 F per F... "FF-[-F+F+F]+[+F-F-F]" has F count = 2+3+3 = 8. So 8^n — gen 5 = 32768 F's. Too many. Use max expansion limit and maybe interpret at lower detail.

Alternative: axiom "X", X → "F[+X][-X]FX", F → "FF". Then X count 2^n, F count grows... gen 5: strings grow ~ maybe a few thousand. Let's compute: |X_{n+1}| = 2|F_n| + 3|X_n| ... complex. Simpler: use F → "F[+F]F[-F]F" (each F → 5 F? no: F,F,F,F,F = 5 F's). 5^5 = 3125 F's plus brackets → ~ 3125*... string length ~ 5^n * 6 chars ≈ 18k chars at gen 5. Segments = 3125, fine.

Actually with angle 25°, "F[+F]F[-F]F" is a nice bushy tree. Let's use angle 22° and rule F → "F[+F][−F]F[+F]..." hmm.

Let's go with axiom "F", rule F → "FF+[+F-F-F]-[-F+F+F]" (the classic Wikipedia "tree" one), angle 25°. F count per F: 2 + 3 + 3 = 8. Gen 5 = 8^5 = 32768 segments. That's a lot but p5 can draw 32k lines... maybe too slow at 60fps. Cap: max segments ~4000; if exceeded, reduce by... Better limit generation effect by scaling: choose a rule with modest growth, e.g. F → "F[-F][+F][F]" (4 F's) → 4^5 = 1024 segments at gen 5. That's nice and bushy. Angle 20°.

Hmm, "F[-F][+F][F]" gives branches at each node with 3 branches + continuation. Nice tree.

Let's define:
- axiom: "F"
- rules: { "F": "F[-F][+F]F" } → 3^n F's: gen5 = 243 segments. Bit sparse. With F→"FF" too? Let's do rules: F → "FF-[-F+F]+[+F-F]" hmm.

Let me just compute lengths for candidate: F → "F[+F][−F]F" gives 3 F per F: gen5 = 243 segments, string length ~ 243 * 8 = 1944. Tree: each node has 2 side branches and continues. Looks decent but thin at gen 5? Actually depth 5 of recursion — fine, it's a fractal tree.

Better: F → "FF+[+F-F-F]-[-F+F+F]" but limit generation string by capping: since gen 1..5, gen 5 = 32768 segments — too heavy. We could scale down segment length; 32k lines at 60fps in p5 with beginShape... risky.

Compromise: rule F → "F[+F]F[-F][F]" (5 F's) → 5^5 = 3125 segments. With stroke lines each frame plus sway recursion... 3125 line() calls per frame is fine (p5 can do that). Plus leaves at tips maybe ~ hundreds. OK.

Hmm, but recursion for sway: we draw segments in order with iterative stack computing absolute angles — fine.

Actually let's think about the structure more concretely.

Parsing: turtle with stack.
For each char:
- 'F': create segment from current pos with current angle, length L, parent = current parent chain. Push segment, current parent = new segment.
- '+': angle += ruleAngle
- '-': angle -= ruleAngle
- '[': push state (pos, angle, parent)
- ']': pop state

Each segment: {parent, localAngle (angle - parent's angle... but easier store absolute base angle and compute), len, depth}

For sway drawing: recursively traverse segments in order (they're created in DFS order via bracket push/pop... actually creation order is DFS since brackets emulate recursion). But parent index < child index always. So we can iterate in order and maintain absAngle[i] = absAngle[parent] + (angle_i - angle_parent) computed at build time... Let's store turn = baseAngle_i - baseAngle_parent (for root, turn = baseAngle). Then at draw: absAngle_i = absAngle_parent + turn_i + sway_i.

Sway: sway_i = windAmp * sin(time*windSpeed + seed + depth_i*0.7 + phase_i) * min(1, depth_i/maxDepth) ... We want tips to sway more but stay attached — since we compute positions cumulatively (x_i = x_parent_end + cos(absAngle_i)*len*progress), children stay attached automatically.

But positions must be recomputed each frame during sway — that means we compute positions during drawing anyway. But for the fit-to-view scale, we need static positions (no sway). Compute static layout once at build: static positions and bbox; then each frame draw with sway but apply scale/offset computed from static bbox. With sway amplitude small, add margin. Good.

Growth: each segment has growthStart = cumulative distance from root to its start, growthEnd = cumulative distance to its end. Total = max. Progress p in [0,1] mapped to distance d = p*total. Segment fully drawn if growthEnd <= d, partially if growthStart < d < growthEnd (draw partial length). This gives growth from trunk to tips. 

Leaves: at segments whose children count == 0 (tips), draw a leaf at end when d >= growthEnd; scale leaf in with a little pop over a fraction of time. Also could add small leaves on outer branches.

Leaves as ellipses rotated with branch angle, colored with gradient palette.

Colors: background dark navy / gradient sky, trunk brown gradient (stroke color by depth: brown → green), leaves in green/pink blossoms.

Controls: HTML overlay: generation slider (1..5) with label, Regrow button, maybe wind slider? Not required but "generation control from 1 to 5 and Regrow". Keep it simple: range input + buttons +/- maybe. Use a range input styled, plus Regrow button. Also display status text like "Generation 3 — growing 42%".

p5 usage: global mode with setup/draw. Canvas sized to container, e.g. window sized canvas with resize. Keep it simple: createCanvas(windowWidth, windowHeight) with a resize handler... keep fixed to window size and recompute on windowResized.

Also "Regrow" restarts growth — randomize wind seed but same grammar, same generation. Also could randomly vary the grammar? No — "restarting growth using the same chosen grammar" — so keep grammar fixed (maybe allow choosing? not required). Keep the grammar fixed.

"Changing generation or pressing Regrow restarts growth using a different branching structure" (verify: "Change the generation setting and check that growth restarts with a different branching structure"). Different generation → different structure. Good.

Let me write code.

Constants:
RULE = { 'F': 'FF+[+F-F-F]-[-F+F+F]' } too big. Let's do:
axiom = "F"
rules = { "F": "F[-F]F[+F][F]" } — hmm let me pick something visually nice.

Classic "tree 2" from Wikipedia: 
axiom "F", rule F → "F[+F]F[-F]F", angle 25.7°. F count 3^n = 243 at gen5. Segments 243. Fine and clean.

Maybe better lush: rule F → "FF+[+F-F-F]-[-F+F+F]" but with generation cap making gen 5 huge. Let's estimate char counts: F→8 F's plus other chars: string "FF+[+F-F-F]-[-F+F+F]" length 20 chars with 8 F. So |s_{n+1}| = |s_n| - F_n + 20*F_n... roughly s_n ≈ 20 * 8^n /7... gen5: 8^5=32768 F, string ~ 82000 chars. Segments 32768. Too heavy for smooth animation.

Go with F → "F[+F][−F]F" style but slightly richer: F → "FF-[-F+F+F]+[+F-F-F]" is the same as above.

I'll use: axiom "F", rule F → "F[+F][−F]F[−F][+F]"? That's 6 F per F → 6^5 = 7776 segments. Hmm.

Let's pick F → "F[-F][+F]F" (3 F) but with an additional F → "FF"? Two-rule: F → "FF+[+F-F-F]-[-F+F+F]" no.

Simplest good-looking: 
axiom: "F"
rules: { "F": "F[+F]F[-F]F" } angle 25.7, segment length shrink? For an L-system with constant segment length, gen n tree size grows 3x in extent... "keep the whole tree visible" handled by auto-fit scaling. Good — auto-fit handles it.

Actually the growth of extents: at gen 5, tree is large but scaling to fit shrinks segments to tiny. That's fine (fractal look). Maybe scale length as L0 / (1.35^gen) so it stays reasonable, then autofit as safety.

Number of segments 3^5 = 243 at gen 5 — modest but fine. Let's make it richer: F → "FF+[+F-F-F]-[-F+F+F]" limited... 

Alternative approach for richness: allow rule with 5 F: F → "F[+F][-F]F[+F]" ... 

Let me evaluate 5^5=3125 segments; drawing 3125 lines/frame is definitely fine in p5 (canvas 2D). Leaves at tips: number of tips grows too — for F→F[+F][−F]F[+F][−F]? tips ~ leaves count maybe 1000 ellipses, still ok.

Let's use: axiom "F", rule: F → "FF-[-F+F+F]+[+F-F-F]" (8 F) but cap expansion with a maxLength guard: expand only up to N generations but if string exceeds MAX_CHARS (e.g. 20000), stop expanding further (bound grammar expansion requirement!). And also maybe interpret with skipping. Hmm but then gen 5 might render same as gen 4 — not great.

Decision: rules = { "F": "F[+F][−F]F" }, angle = 24°. Segments 3^n: gen1=3, gen2=9, gen3=27, gen4=81, gen5=243. Hmm gen 5 with 243 segments is a bit sparse for "lush". 

Let's do two rules:
"X" → "F[+X][−X]X" ... classic plant: axiom "X", X→"F[+X][-X]FX", F→"FF", angle 25°. Then X count 2^n, F count grows 2^n-ish per level; total string length at gen 5 ~ let's compute. Let x_n = count X, f_n = count F, s_n = total length. X → "F[+X][-X]FX": contributes 2 F, 2 X, and fixed chars 8. F → "FF": 2 F, length 2.
x_{n+1} = 2 x_n; f_{n+1} = 2 f_n + 2 x_n; 
x_0=1,f_0=0: x1=2, f1=2; x2=4, f2=2*2+2*2=8; x3=8, f3=2*8+2*4=24; x4=16, f4=2*24+2*8=64; x5=32, f5=2*64+2*16=160.
Total F = f5 = 160 segments at gen 5. Too sparse again.

OK the "8 F" rule: F→"FF+[+F-F-F]-[-F+F+F]", F counts 8^n: gen1=8, 2=64, 3=512, 4=4096, 5=32768. gen4 = 4096 segments is quite nice, gen5 32768 too much. Could handle gen5 by capping: if segments > MAX (e.g. 6000), subsample? That breaks structure.

Alternative: use rule with 5 F: F → "FF-[-F+F]+[+F-F]" — F count = 2+1+1... "FF-[-F+F]+[+F-F]": F's = 2 + 2 + 2 = 6. 6^5 = 7776. Slightly heavy but likely OK if we draw with plain lines and no per-frame allocation issues. 7776 lines + maybe ~2000 leaves per frame... p5 draw might drop to 30fps but acceptable. Hmm, risky.

Let's use 4 F rule: F → "FF-[-F+F]+[+F-F]" no. Use F → "F[+F][−F]F" wait that's 3. Or F → "FF[+F][-F]F" → 4 F per F: 4^5 = 1024 segments at gen5, 256 at gen4, 64 gen3, 16 gen2, 4 gen1. That's a nice progression. String length: per F expansion 12 chars → 12*4^5 ≈ 12k chars — fine, and we can bound with MAX_EXPANSION_CHARS = 20000 and MAX_SEGMENTS = 4000 (safety).

Rule: F → "FF[+F][-F]F"? Structure: F F, then branch +F, branch -F, then F. Hmm, "FF" then branches then continuation... let's instead use F → "F[-F][+F]F" ... eh. I'll go with "FF-[-F+F]+[+F-F]"? count F: F,F,-,-,F,F,],+,[,+,F,-,F,] = 2+2+2 = 6.

Final: axiom "F", rule F → "FF[+F][-F][+F]"? Let's just choose a well-known pretty one at moderate size:

Rule: F → "F[-F][+F][F]" — F count 4: F, F, F, F? "F[-F][+F][F]" → F's: 1 + 1 + 1 + 1 = 4. Yes 4 F. Structure: node continues F, branches left F, branches right F, branches straight F. That's a nice bushy tree. Angle 20°.

Hmm, "F[-F][+F][F]" — at each step the main stem continues and two side branches + one inner. Actually with length ratio constant, this creates a nicely dense canopy. 4^5 = 1024 segments. 

But actually the classic that looks best: F → "FF+[+F-F-F]-[-F+F+F]" scaled... I'll go with my 4-F rule and visually check with screenshots.

Wait — actually to make it look more tree-like (trunk, then branches), I might use a longer segment at low depth and shrink. Constant length is standard L-system; auto-fit scaling keeps it visible. Fine.

Also add: segments' stroke width based on depth (thicker near trunk), color lerp from brown to green.

Let me now think about auto-fit. Compute static layout positions: for each segment, start point and end point (base angle, no sway). bbox over all points. scale = min((W-2m)/bboxW, (H-2m)/bboxH). offset centers. Apply as translate/scale in draw: translate(offsetX, offsetY); scale(s). But strokeWeight scales with scale() — set strokeWeight(w / s) to keep constant screen width. Or compute positions in screen space manually. Simpler: apply transform and set strokeWeight(weight/scale).

Alternatively compute in world space and multiply positions by scale in code. Transform approach is fine.

Also handle gen 1 tiny tree: bbox small → scale huge → stroke weights handled.

Wind sway during draw: positions computed dynamically. Since we draw in creation order and parent index < child index, we can iterate:
absAngle[0] = baseTurn[0] + sway(0)
xEnd[i] = xStart[i] + cos(absAngle[i]) * len_i * grow_i; yEnd similarly
xStart[child] = xEnd[parent] (children start at parent's end). For '[' pushed states, the branch starts at the current position at push time — which is the current point's... Hmm. In turtle: when we push state (pos, angle, parentSegment), the branch's segments start at that pushed position, which is the end of the current parent segment. So each segment stores its parent segment and offset: start = parent's end point (with sway). But when '[' pushes mid-segment? No — '[' only occurs between segments in our grammar (F commands). So each segment's start = end of its parent segment. Root segment starts at origin.

But careful: a segment's children include both the continuation and branch segments that all start at its end. Yes — with our grammar each F's children begin at its end. Good.

So define segments array where seg.parent = index of the segment whose end is this seg's start (or -1 for root). Draw in index order (parents always before children because we create parent F before its children in the string... wait: in "F[-F][+F]F", the first F is created, then bracket children, then the continuation F. All children come after parent in creation order. Yes.)

But sway: if child's absAngle = parentAbsAngle + turn + sway, and child starts at parent's end, attachment holds. But sway should apply at branch points: child sway should differ per branch. We'll compute sway per segment as a function of its own depth and a per-branch phase: sway_i = windAmp * noise-ish: amp_i * sin(t*speed + seed + depth_i*0.9 + phase_i) where phase_i = per-segment hash. However if the continuation child has same depth... it's fine, it'll look like leaves fluttering.

To keep it physically plausible-ish, sway magnitude grows with depth: amp = baseAmp * (depth_i / maxDepth)^1.2, plus a global gust factor.

Good enough.

Growth animation: growth timeline. d from 0 to totalLength over ~ (2.5 + gen*0.5) seconds. Each segment: draw fraction f = clamp((d - startDist)/len, 0, 1). Then children start positions must use the parent's *current drawn end* point during growth! Yes — since child starts at parent's end, and if parent is partially drawn, the child should start at the partial end and ideally not draw until parent is complete... Actually to keep attachment, children start at parent's current end (partial). But children's growth startDist = parent's endDist, so children are not drawn until parent complete — so during partial parent drawing, no children exist yet. But then children's start point = parent's fully drawn end. Fine. But careful: if child's startDist > d, skip. And when parent is partial, children have f=0. Good. So use xEnd as computed with partial length — consistent.

Leaves: at tips (segments with no children) once f==1, draw leaf at end with pop animation based on (d - endDist) relative to some window. Also maybe leaves on all segments at high depth? Just tips plus maybe small buds. Keep tips only.

Actually many tips at gen 5 (~ hundreds) → leaves ~ hundreds. Fine.

Now UI: fixed panel top-left with title, description of grammar (axiom, rules, angle), generation slider 1-5, Regrow button, growth status. Also maybe a "Wind" slider — optional, adds value but not required; I'll include a small wind slider? Task says styling free. Keep controls: generation slider + Regrow. Maybe add wind slider — it's extra; fine but must not break. I'll include it (small).

Actually the verification: "Change the generation setting and check that growth restarts with a different branching structure." So generation change triggers rebuild + restart growth.

Also "Bound grammar expansion" — implement expandLSystem with maxIterations and maxStringLength cap (stop early with a warning maybe). And MAX_SEGMENTS cap during interpretation.

Let's write the code.

```js
const GRAMMAR = {
  axiom: "F",
  rules: { "F": "F[-F][+F][F]" },
  angle: 22
};
const MAX_STRING = 20000;
const MAX_SEGMENTS = 4000;
```

Hmm wait: with rule "F[-F][+F][F]", the 'F' inside brackets are full segments at same length — canopy gets wide. OK.

expand:
```js
function expandLSystem(gen) {
  let s = GRAMMAR.axiom;
  for (let i = 0; i < gen; i++) {
    let out = "";
    for (const ch of s) {
      const r = GRAMMAR.rules[ch];
      out += (r !== undefined) ? r : ch;
      if (out.length > MAX_STRING) { out = out.slice(0, MAX_STRING); return { str: out, truncated: true, gen: i+1 }; }
    }
    s = out;
  }
  return { str: s, truncated: false, gen };
}
```

interpret(str): build segments.

```js
function buildTree(str) {
  const segs = [];
  const stack = [];
  let x=0,y=0,ang=-Math.PI/2, parent=-1;
  let dist = 0; // cumulative distance from root along drawn path
  // we need dist along the path to each segment start: store seg.startDist
  for (const ch of str) {
    if (ch === 'F') {
      if (segs.length >= MAX_SEGMENTS) break;
      const turn = parent === -1 ? ang : ang - segs[parent].baseAngle; // hmm
      ...
    }
  }
}
```
Simpler: store seg.baseAngle = ang (absolute base angle), and turn computed at draw as (seg.baseAngle - parent.baseAngle). Root turn = baseAngle.

seg = { parent, baseAngle: ang, len: LEN, depth: parent===-1?0:segs[parent].depth+1, startDist: dist, endDist: dist+LEN, children: [] }
x += cos(ang)*LEN; y += sin(ang)*LEN; dist += LEN; parent = segs.length (index).

But wait — dist is cumulative along the current turtle path including backtracking? When we ']' pop state, we return to earlier position and dist should revert to the pushed dist. So stack stores {x,y,ang,parent,dist}. Yes.

Also '[' push: {x,y,ang,parent,dist}. ']' pop: restore.

Also add children counts: after building, compute for each seg number of children to find tips: iterate segs, if seg.parent>=0 segs[parent].childCount++. Also track maxDepth.

Then compute static layout: iterate segs in order: sx = parent? parent static end : 0; static end = sx + cos(baseAngle)*len... store for bbox. Actually we can compute bbox from start/end points.

Then growth total = max endDist.

Draw:
```js
function drawTree(growDist, time) {
  const absAngle = new Array(n), ex = ..., ey = ...
  for i: 
    const p = seg.parent;
    const parentAngle = p<0 ? -PI/2 : absAngle[p];  // hmm root baseAngle already -PI/2
    const turn = seg.baseAngle - (p<0 ? seg.baseAngle : segs[p].baseAngle);
    const sway = windAmp * swayEnv * Math.sin(time*windSpeed + seg.phase + seg.depth*0.7) * Math.pow(seg.depth/maxDepth, 1.1) ... 
    absAngle[i] = parentAngle + turn + sway;
    const f = clamp((growDist - seg.startDist)/seg.len, 0, 1);
    const sx = p<0 ? 0 : ex[p], sy = p<0 ? 0 : ey[p];
    ex[i] = sx + cos(absAngle[i])*seg.len*f; ey[i] = sy + sin(absAngle[i])*seg.len*f;
    if (f>0) draw line(sx,sy,ex,ey) with color/width by depth; 
    if (f>=1 && childCount===0) drawLeaf(ex,ey,absAngle[i], seg, time)
}
```
Wait — root baseAngle is -PI/2 and parent is -1: turn = seg.baseAngle - seg.baseAngle = 0 → absAngle = parentAngle(-PI/2) + 0. Fine if I set parentAngle for root = -PI/2 and turn 0. Or just handle: turn = p<0 ? 0 : seg.baseAngle - segs[p].baseAngle, parentAngle = p<0 ? -PI/2 : absAngle[p]. But careful: seg.baseAngle for root is -PI/2 already so it works either way. Use that.

Sway at depth 0 should be ~0 (trunk base fixed): amp = pow(depth/maxDepth, 1.2) → root depth 0 amp 0. But if maxDepth = 0 (gen... always ≥1 so maxDepth ≥ 1). Good.

Growth speed: totalDist known; growth duration = clamp(totalDist/... ) Let's set duration seconds = 2.2 + 0.35*gen, and animate growDist = easeOut? Linear is fine, or use ease so it's smooth. Use easeInOut-ish: growProgress = 1 - pow(1-t, 1.6) maybe. Simpler: linear with slight easing.

Actually totalDist can be huge at gen5 (1024 segments * LEN). Time-based progress independent of size is fine.

Wind: continuous. windAmp = base 0.045 rad * gust factor where gust = 0.6 + 0.4*sin(t*0.3) etc. Plus wind slider multiplies.

Leaves: color varies per leaf via hash: green shades, some pink blossoms at higher gens? Let's do green leaves with slight hue variation, and small blossoms (pink) randomly on ~15% of tips. Use sin-based pseudo random from index.

Leaf drawing: ellipse rotated to absAngle; size ~ LEN*0.35 clamped screen size? Since world space is scaled by `s`, leaf size in world units would scale with tree. Use leafSize = seg.len * 0.5 maybe, with min/max. Fine.

Also pop animation: leafScale = clamp((growDist - seg.endDist)/(seg.len*1.5), 0, 1) eased.

Colors:
- background: vertical gradient sky (draw with rects or a few lines) — draw gradient using a loop of rects in screen space before transform.
- trunk color: lerp from #6b4a2f (brown) at depth 0 to #2f6d3a green at maxDepth. strokeWeight: map depth 0..maxDepth to 7..1, but scale with tree size — use world weight = ... Since we apply scale(s), strokeWeight(w/s). Let's compute worldWidth = map(depth) * (something like LEN*0.12) so it scales with tree automatically. Then screen width = worldWidth * s. Hmm, when tree is small (gen 1) and scaled up hugely, widths scale too — good, keeps proportion. Let's set strokeWeight(worldW) inside transformed context and it scales automatically. But min screen width 0.75 px. Let's compute: weight = max(0.6/s, worldW). Good.

Ground: maybe a soft ground ellipse/hill at bottom. Optional nicety. Add subtle ground shadow ellipse under tree — but tree base is at origin which we map to bottom-ish of canvas. bbox includes the tree from y=0 downward (since -PI/2 goes up, y negative). Auto-fit centers bbox in canvas — the trunk base would be near bottom edge of the fitted box. Fine.

Let's set canvas fill area: full window with panel overlay.

Now write the HTML file. Include <script src="p5.min.js"></script> then my script.

Check the file exists in cwd first.

Then run browser to verify.

Let me write the code now carefully.

Pseudo-random: 
```js
function hash(i){ const x = Math.sin(i*127.1 + seed*311.7)*43758.5453; return x - Math.floor(x); }
```
seed changes on Regrow.

UI HTML:
```html
<div id="panel">
  <h1>L-System Tree</h1>
  <div class="grammar">axiom: F<br>rule: F → F[-F][+F][F]<br>angle: 22°</div>
  <label>Generation <span id="genVal">3</span></label>
  <input type="range" id="gen" min="1" max="5" step="1" value="3">
  <button id="regrow">Regrow</button>
  <label>Wind <input range></label>
  <div id="status">...</div>
</div>
```

Status: "Generation 3 · growing 45%" or "grown · 243 branches · wind swaying".

Keyboard: arrow keys? Not needed.

Now p5 setup:

```js
let tree = null; // {segs, maxDepth, total, bbox, ...}
let growthStartMs = 0;
let windLevel = 1;

function setup() {
  createCanvas(windowWidth, windowHeight);
  ...
  rebuild(3);
}
```
On windowResized: resizeCanvas, recompute fit.

Fit computation each frame is cheap: compute scale from bbox in draw (depends on width/height). Do it in draw: 
```js
const margin = 40;
const bw = max(bbox.w, 1), bh = max(bbox.h, 1);
const s = min((width-2*margin)/bw, (height-2*margin)/bh);
const ox = width/2 - (bbox.minx + bbox.maxx)/2 * s;
const oy = height/2 - (bbox.miny + bbox.maxy)/2 * s;
```
Then translate(ox,oy); scale(s).

bbox in world coords where trunk base at (0,0), tree extends up (negative y) and sideways.

Now let's handle growth restart on generation change: rebuild tree, growthStart = millis().

Let me also make sure leaves don't appear at gen 1 weirdly. Fine.

Segment colors: use lerpColor between trunkColor and tipColor based on depth/maxDepth, plus a slight wind/light shimmer? Keep simple.

I'll draw branches as lines with round caps. Use strokeCap(ROUND) — but that's a global context setting; fine.

Perf: 1024 line() calls + leaves. Fine.

Actually careful: drawing each line with stroke() color per segment — could batch by grouping into color buckets, but 1024 is fine.

Let me write it.

For the sky gradient, draw once per frame in screen space:
```js
function drawSky(){
  const c1 = color(12,18,38), c2 = color(52,84,140)... 
  for (let i=0;i<40;i++){ ... }
}
```
40 rects per frame is fine. Or use drawingContext gradient (canvas API) — allowed since p5 exposes drawingContext. Use createLinearGradient — simple and fast:
```js
const ctx = drawingContext;
const g = ctx.createLinearGradient(0,0,0,height);
g.addColorStop(0,'#0b1026'); g.addColorStop(0.55,'#28406e'); g.addColorStop(1,'#6a8fc0');
ctx.fillStyle = g; ctx.fillRect(0,0,width,height);
```
Good, no external resources.

Also add subtle sun/moon glow and stars? Skip stars maybe, or add a few dots — keep light.

Ground: draw a soft dark ellipse at the tree base in screen space (after computing where origin maps to): use the transform: draw ellipse at (0,0) with rx = bbox.w*0.6, ry small — under the tree, dark green ground mound. Nice.

Now leaves color: greens with variation + blossom pinks. Let's compute leaf color = lerpColor(color('#7fc96b'), color('#2e7d4f'), hash) and blossom if hash2 < 0.12 → pink '#f2a6c8'.

Leaf shape: ellipse(0,0, size, size*0.55) rotated to angle + slight flutter rotation from wind.

Implementation detail: p5's `push()/pop()` per leaf (hundreds) fine.

Let me now write the file.

One more consideration: "progressive growth from the trunk toward branch tips" — using distance-from-root ordering does that. Good.

Write code:

```js
const GRAMMAR = {
  name: 'Branching tree',
  axiom: 'F',
  rules: { 'F': 'F[-F][+F][F]' },
  angle: 22,
  step: 10
};
```

Hmm the step length: with constant step 10 in world units and gen5 with 1024 segments spread across depth 5... Tree height? Each level adds step along a direction; total path length 1024*10, but spatial extent maybe ~ 100-200 units. Auto-fit handles it. But stroke width should be relative: use width = max(0.7/s, map(depth,0,maxDepth, 5.5, 1.0)) in world units? If the tree extents are ~200 world units, a 5.5 world-unit trunk = 2.75% of tree width — reasonable. But for gen1 (extent ~30), trunk width 5.5 is 18% — too fat. Let's compute width proportional to tree size: trunkW = extent * 0.035 where extent = max(bbox.w, bbox.h). Then tipW = trunkW*0.12. Then in screen space the trunk is 3.5% of the tree's on-screen size — consistent across generations. 

But since we draw inside a scaled transform, strokeWeight(w) uses world units scaled. Set strokeWeight(max(0.6/s, lerp(trunkW, tipW, depth/maxDepth))). Good.

Now code writing. Let me write the whole thing.

```js
let tree, growthStart, seed = 1, gen = 3, windLevel = 1;
let growing = true;

function rebuild(newGen) {
  gen = newGen;
  const { str, truncated, gens } = expand(gen);
  tree = buildTree(str);
  tree.truncated = truncated;
  growthStart = millis();
  growing = true;
}
```

In draw:
```js
const t = (millis() - growthStart)/1000;
const dur = 2.2 + gen*0.5;
let p = t/dur; 
const growDist = tree.total * easeOutQuad(clamp(p,0,1)) ... 
```
Actually linear growth of distance is more like real growth. Use pLinear = clamp(t/dur,0,1) then growDist = total*p. Fine, maybe smooth start: p = p*p*(3-2*p) (smoothstep) makes start slow. Use smoothstep-lite: p = 1-Math.pow(1-p,1.7).

Growing flag for status.

Wind: swayEnv computed as:
```js
const gust = 0.55 + 0.45*Math.sin(t*0.31 + seed) * Math.sin(t*0.13 + 1.7);
const windAmp = 0.06 * windLevel * (0.6 + 0.8*Math.max(0, gust));
```
Fine.

Let me just write it and test visually.

Time budget: 15 min. Let's go.

Status text update via DOM each ~100ms to avoid layout thrash (fine either way).

Write the file now.

Also need: `function windowResized(){ resizeCanvas(windowWidth, windowHeight); }`.

Note p5 global mode auto-runs setup/draw. Good.

Leaf drawing detail: at tips we also want leaves along outer branches for lushness. Optional: draw a leaf on segments whose depth >= maxDepth-1 and childCount<=1. Let's draw leaves on tips only + small buds. Keep it simple: tips.

Number of tips at gen5 for rule F[-F][+F][F]: each F produces 3 child F inside brackets + 1 continuation... wait: "F[-F][+F][F]" = main F, then three bracketed F's, and the last F is inside bracket [F]. So structure: F with children: [-F], [+F], [F] — three branches, and no continuation outside! Because after "[F]" the string ends. Hmm — so "F[-F][+F][F]" means every F spawns 3 branches at ±angle and 0. That's a symmetric bush. Tips = 3^n = 243 at gen 5? Each F → 3 F, so segs = 3^gen = 243 at gen5. Sparse-ish and symmetric-bush-like, not tree-like (no dominant trunk).

Better: "FF-[-F+F+F]+[+F-F-F]" is real tree-like but 8^n.

Let's design: F → "F[-F]F[+F]F": continuation dominant. F count = 4? "F[-F]F[+F]F": F, F, F, F, F = 5 F. Hmm: chars: F [ - F ] F [ + F ] F → F's: 1,2,3,4,5 → 5 F. 5^5 = 3125. Heavy-ish but maybe OK... at gen 5, 3125 line calls + ~600 leaves. p5 draw at 60fps? Each line() call is a JS function call with state change; 3125 is fine actually (canvas can do 10k lines/frame).

But string length: each F expands to "F[-F]F[+F]F" = 11 chars → string length ≈ 11*5^5 ≈ 34k chars > MAX_STRING 20000. Would truncate. Raise MAX_STRING to 60000? Building a 34k string char by char is fine. Segments 3125 < MAX_SEGMENTS 4000. Hmm, but the tree at gen5 with 3125 segments of constant length: spatial extent grows ~ (something)^5. Auto-fit shrinks it; the visual will be a dense fractal. OK.

Alternatively use 4 F rule with trunk continuation: F → "F[-F][+F]F": F's = 4? chars: F [ - F ] [ + F ] F → F, F, F, F = 4 F. Structure: main F continues, with two side branches at ±angle, and the continuation F. Wait the last F is the continuation (outside brackets). Yes! So F → "F[-F][+F]F" is: stem F, branch -F, branch +F, stem F. Nice tree shape: 4^5 = 1024 segments. String length ≈ 9 * 4^5 = 9216 chars. 

I'll use that: axiom "F", rule F → "F[-F][+F]F", angle 20°.

Hmm, at gen 5 the canopy will look reasonable. Let's go and check screenshots.

Tips: number of tips ~ number of F at max depth... roughly 3/4 * 1024 ≈ 700 leaves. That's fine but maybe heavy-ish; ok.

Leaves only on tips → many. Fine, ellipses are cheap.

Let me write now.

For pseudo-random phases per segment: seg.phase = hash(i)*Math.PI*2 where hash uses seed.

Alright — writing the file.

Also I want branch stroke color: lerp from #5b3a24 (dark brown) at depth 0 to #3e8f52 (green) near tips. And with a slight lighter tint based on hash.

Draw order: leaves after all branches (so leaves are on top)? But then leaves of inner tips overlay outer branches — acceptable. Actually drawing leaves in segment order is fine too. I'll draw branches first in one pass, then leaves in a second pass.

Let's write.

I'll write the file with `write` tool.

Final check items for verification: initial output, console errors, growth animation, generation change, wind motion, Regrow.

Code:

```js
'use strict';

// ---------- L-system grammar ----------
const GRAMMAR = {
  axiom: 'F',
  rules: { 'F': 'F[-F][+F]F' },
  angleDeg: 20,
  step: 10
};
const MAX_STRING = 60000;
const MAX_SEGMENTS = 5000;

function expandLSystem(gens) {
  let s = GRAMMAR.axiom;
  let truncated = false;
  let used = 0;
  for (let i = 0; i < gens; i++) {
    let out = '';
    for (let j = 0; j < s.length; j++) {
      const r = GRAMMAR.rules[s[j]];
      out += r === undefined ? s[j] : r;
      if (out.length >= MAX_STRING) { out = out.slice(0, MAX_STRING); truncated = true; break; }
    }
    s = out; used++;
    if (truncated) break;
  }
  return { str: s, truncated, gensUsed: used };
}
```

buildTree(str) as described.

Then p5 code.

Let me write it all out concretely in the file.

DOM status element updates: `document.getElementById('status').textContent = ...`.

Gen slider: `input` event → rebuild(parseInt(value)). Regrow button → seed = Math.floor(Math.random()*1e6); rebuild(gen).

Also maybe keyboard 'r' for regrow. Optional.

Let me write the code file now.

Now write index.html.

The file is saved. Now quickly verify in the browser: initial output, console, growth, generation change, wind. Keep it fast.

Grammar works: bounded, 1024 segments at gen 5, maxDepth 31 (good for sway gradients). Now browser check.

Note maxDepth 31 at gen 5 — depthFrac fine.

One concern: buildTree has leftover junk line `const sx = p ? p.sx + ... : 0;` unused variable — harmless but let me clean it. Also `strokeCap(ROUND)` in setup — fine in p5.

Let me quickly test in browser.

Now run in browser.

Rendering works, no JS errors. Problems visible:

1. The tree is tiny — the bbox is computed for the *fully grown* tree (gen 3 extents) but only 5% grown so the visible trunk is a stub. That's expected mid-growth. But the fit uses the full bbox so the grown tree will fill. However the tree appears very low in the canvas — actually it's centered on the bbox, and the trunk stub is at the bottom of the bbox... wait, the bbox center should put the tree center at canvas center. The stub appears at y≈710 which is below center (400). Hmm: bbox minY/maxY for gen3 tree... the trunk base is at (0,0) and the tree extends up (negative y) and sideways. bbox center maps to canvas center. The trunk base (0,0) maps to somewhere in the lower half — appears at y=710, meaning bbox is mostly above y=0? Actually the ground ellipse drawn at (0,0) appears at y≈770 which is near the bottom. So the tree occupies from y≈0 down to... bbox height includes negative y up to maybe -... Since base at 0 and tree goes up, bbox spans minY=-h..maxY=+something. The base at 0 maps near the bottom of bbox → y≈710 out of 800. Fine; the canopy will be above. But the tree being tiny at 5% growth is fine.

Wait, but the ground ellipse appears huge relative — gw = bb.w*1.35. Fine.

2. Status text shows "growing·5%..." — the dot and text overlap? "growing · 5% of the path" shows as "growing·5% of the path" with weird overlap: text "growing" and "5%..." overlapping? Looks like `updateStatus(true)` at rebuild sets status with growDist undefined → clamp01(0/total)=0... Actually in rebuild I call updateStatus(true) with grown=true → text "Generation 3 · fully grown...". Then draw updates. The rendering shows "growing·5%..." with overlapping characters — that's just the image render of inline spans; likely fine but the display shows overlapping text "growing" and something. Looking closely: "growing" then "·5% of the path" overlapping. Probably the statusText and something else. Hmm, could be the rendering of `Generation 3 · growing · 5% of the path` too long for the 266px panel and it's just clipped/wrapped oddly? The visible text is "growing·5% of the path" — that suggests the beginning "Generation 3 · " is missing/overlapped. It might be text wrapping with the dot. Actually the panel width 266px, font 11px — "Generation 3 · growing · 5% of the path" would wrap into 2 lines. The screenshot shows one line at y≈395 overlapping the border-top area. It seems like the text is there but rendered oddly in screenshot. Let me check again with a screenshot later.

Let me wait a few seconds and screenshot to see the grown tree and check status.

Main risk: growth is slow-ish; let's take a motion/screenshot pass. Let me wait ~4s by doing other actions, then screenshot.

Also gen3 = 64 segments, quite sparse visually. maxDepth 7. Gen 5 = 1024 segments is the lush one. Default gen 3 may look sparse but fine.

Let me check the grown state.

Now screenshot to see grown tree.

There's an error: "pop is not a function" — this breaks the draw loop! Because in `drawLeaf` I declare a parameter named `pop`, which shadows... no, the issue: `function drawLeaf(x, y, ang, seg, i, pop, t, s)` — the parameter `pop` shadows p5's global `pop()` function inside drawLeaf... but the error "pop is not a function" happens where? Inside drawLeaf I call `push()` and `pop()` — the parameter `pop` (a number) shadows the global `pop` function → `pop()` is not a function. That's the bug!

Fix: rename the parameter to `popAmt` and call pop(). Also in drawGround I don't call pop. Also in draw() `pop()` at the end is fine since no shadowing there.

Also growth is progressing (21% after several seconds) — growth duration gen3 = 3.85s; but 21% after ~5s? Hmm. The timeline: reload frame showed 5%, then 4s sleep + screenshot showed 21% — but the tab may be throttled or growth restarted... Actually the "error: pop is not a function" throws inside draw(), aborting draw each frame at the leaf stage — but the error occurs after branch drawing so growth appears; however, when draw() throws, does millis-based progress still advance? Yes, progress is time-based, but the frame is aborted at first leaf. 21% at ~5s is odd — unless the error caused draw to stop being called? p5 continues calling draw even if it throws? Actually if draw throws, p5's loop may stop entirely... but the % changed from 5 to 21, so it's still updating. Possibly the browser tab rendering is slow/frame-limited. Whatever — fix the pop bug and re-check.

Also potential issue: the growth seems slow because `t` computed from growthStart... whatever, after fix let's measure.

Another observation: the trunk stub is drawn but branches look thick and short — at 21% it's fine.

Let me fix the shadowing bug and also rename the loop var `p` for progress (fine).

Also the earlier status overlap in the first screenshot was just text wrap.

Fix now.

Also the drawLeaf signature call passes `pop` variable in draw — that's fine (local const pop in draw, not shadowing inside draw since draw doesn't call pop()... wait, draw DOES call pop() at the end: `pop();` and declares `const pop = f * f * (3 - 2 * f);` inside the for loop block scope — `const pop` is block-scoped to the for-loop body, so it doesn't shadow outside. But within that block, we call drawLeaf(..., pop, ...) — fine. OK.

Hmm, careful: `const pop` inside the second for loop's block. The `pop()` call at the end of draw() is outside that block. Fine.

But wait — actually there might be an issue: `const p = clamp01(...)` at top of draw, and `pop()` — no conflict.

Now reload and check.

No error now. The status shows "growing·5%..." but text overlapping — that's suspicious. "Generation 3 · growing · 5% of the path" — the panel shows "growing·5% of the path" with overlapping glyphs. It's likely the screenshot compositing of a wrapped line... Actually the DOM in the tool output shows "Generation 3 · growing · 5% of the path" correctly. So DOM text is right; the visual overlap is likely due to the two-line wrap where line 1 "Generation 3 · growing · 5%" and line 2 overlapping? The status div has min-height 32px and the text at 11px would wrap. The screenshot rendering shows garbled overlap — maybe the browser screenshot flattening. Not critical.

Wait — the DOM status says 5% still after reload, and the tree stub is still small. The screenshot is taken at frame 1 (+0ms) so it's right after reload. Fine.

Now wait ~5s and screenshot to see full grown gen-3 tree, then change generation to 5 and check.

But note the growth timing: at frame 1 the status said 5% after reload; the earlier run showed 21% after 4s+ some seconds — suggesting growth is slower than intended. Possibly the p5 draw loop starts later (millis() at rebuild called in setup, fine). Or frame rate low. Let's check after sleeping.

Fully grown gen-3 tree: connected trunk and branches, leaves/blossoms at tips. Whole tree visible, fits canvas. 

Observations:
1. Leaves appear at mid-height too (tips of inner branches) — fine.
2. Top-most tips (depth 7 leaves?) — leaves only at tips; top branches have no leaves? Actually top branches end with leaves... at the top I see branches without leaves. Hmm, tips at depth < maxDepth... no, leaves are drawn for all childless segments. The top branches look bare — maybe the leaves there are just small (leaf size = seg.len*0.62 constant, same everywhere) — no, they'd be the same size. Looking at the top, the fine branches end without visible ellipses... Actually maybe those are leaves not yet popped (pop uses growDist - endDist, and at "fully grown" growDist = total so all should pop). Hmm, at the very top I see thin green lines ending freely. Possibly the top-most segments are non-tip? No.

Let me look again: the top region has many thin green line ends; some appear to have no ellipse. Possibly because leaf ellipse is drawn with `noStroke()` fill green and they're there but small... they'd be similar size to the mid ones (which are clearly visible). Hmm.

Wait — maxDepth=7 for gen 3; depthFrac-based widths. Leaves are drawn for segs with children===0. In the image, mid-level tips have leaves, top-level tips seem bare. That's weird. Unless... the top-most segments are the "continuation" F segments which have children (the next generation's F starts at their end? no—continuation F is a child). Hmm.

Actually maybe the top ones DO have leaves but the leaves are drawn with angle rotate(ang + PI/2) and are thin ellipses, nearly vertical, blending with the branch lines. The mid ones appear as horizontal ovals... they're rotated to angle + 90°. For a branch pointing up, the leaf is rotated to horizontal? ellipse(w,h) with h = 0.58w rotated by ang+PI/2: if ang = -PI/2 (up), rotation = 0 → ellipse wider than tall → horizontal oval. That matches the visible mid leaves which are horizontal ovals. For top branches, angle similar... so they should look the same.

Let me zoom: the top of the tree has branches radiating; some have no leaf. Possibly because leaves at top are behind branches? No.

Hmm — maybe it's just that the top-most tips in the image are the terminal segments at depth 7 and there are 43 tips; visible leaves: I count ~12 large ovals. So many tips lack leaves! Why?

Possible cause: `hash01` — fine. `pop` variable renamed. Leaves drawn in pass 2 only if f>0 where f = clamp01((growDist - sg.endDist)/(sg.len*2.2)). At full growth growDist = tree.total. For a tip with endDist close to total (the deepest path), growDist - endDist ≈ 0 → f ≈ 0 → leaf not drawn / zero size! That's the bug: the longest path's tips get f≈0.

Fix: leaf pop should use time since growth reached that tip, not distance remaining. Better: compute leafPop from the growth progress: since growth is distance-based, define f = clamp01((growDist - sg.endDist)/(tree.total*0.02) + something)... Simplest: when grown (p>=1), set f=1 for all. Or base the pop window on a fraction of total: f = clamp01((growDist - sg.endDist)/(tree.total*0.03)). At full growth, tips with endDist within 3% of total would still be tiny. Better: use time-based: f = clamp01((t - tipTime)/0.5) where tipTime = growthDur * (endDist/total)... same issue: the last tip's pop would complete 0.5s after growth ends — that's fine and desirable! Since at t > growthDur + 0.5 everything is popped.

So: tipReachT = growthDur * (sg.endDist / tree.total); f = clamp01((t - tipReachT)/0.6). At fully grown + 0.6s all leaves fully popped. Good.

Let me implement that: pass `t` and compute in drawLeaf or in draw before. I'll compute pop in draw:
const tipT = growthDur * (sg.endDist / tree.total);
const f = clamp01((t - tipT) / 0.6);

But growth easing: growDist = total*eased(p), so time-to-reach isn't linear. Approximation is acceptable (leaves pop slightly early/late). Fine.

Also: leaf size constant seg.len*0.62 — at gen 5 with lots of segments, leaves may overwhelm. Acceptable.

Another improvement: the top branches look bare partly because leaves pop. After fix, re-check.

Also consider: at gen 5 (1024 segs) with maxDepth 31 — branch widths lerp fine.

Let me also verify wind motion via motion frames after fix.

Time is tight (~3 min). Make the fix now.

Also `updateStatus(grown, growDist)` is called with growDist — fine.

Also consider making leaves a bit smaller at higher generations to avoid clutter: leaf base = max(seg.len*0.62, 3.2/s). At gen 5 seg.len is same (10 world units) but the tree is scaled down, so leaves stay proportional to branches. Fine.

Reload and check gen 5 + wind.

Now change generation to 5 and observe growth restart with different structure, then check leaves and wind. Use browser: reload first (to pick up the file edit), then set the slider.

The browser tool has click/type/key actions. To set the range input to 5, I can click on the slider at the far right position. Slider is at x≈40..266, y≈238. Clicking at x=262,y=238 sets value 5. Let's do: reload, then click slider right end.

Now click the generation slider at its right end (x≈262, y≈238) to set 5. Then screenshot to verify restart + different structure.

Actually the slider thumb position for value 3 is at x≈154. To set value 5, click near x≈262.