Sub-word rhyme highlighting: dim word fill + bright tail underline

Whole rhyming word fills dimly; a bright underline marks just the
rhyming part (tonight -> under 'ight'), so the precise interlock shows
without the fill looking ragged when the phoneme->letter guess is a
letter off. Removed 'scheme' from the toolbar readout.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app.py

@@ -282,6 +282,25 @@ def _grapheme_tail(raw: str) -> str | None:
     return tail
 
 
+def rhyme_char_start(word: str) -> int:
+    """Best-guess character index where a word's rhyming tail begins:
+    take as many vowel-letter groups from the end as the pronunciation's
+    rhyming part has vowels (tonight -> 'ight', creation -> 'ation').
+    Spelling can't map phonemes exactly, so this is an approximation."""
+    ph = phones_for(word)
+    if not ph:
+        return 0
+    nv = len(_tail_vowels(ph)) or 1
+    groups = [m.start() for m in re.finditer(r"[aeiouyAEIOUY]+", word)]
+    # drop a silent trailing 'e' (write, time, fire) so it doesn't eat a slot
+    if (len(groups) > 1 and word[-1] in "eE"
+            and groups[-1] == len(word) - 1):
+        groups.pop()
+    if len(groups) < nv:
+        return 0
+    return groups[len(groups) - nv]
+
+
 def rime_keys(word: str) -> tuple[str, ...]:
     """Perfect-rhyme keys, one per candidate pronunciation."""
     cands = phones_candidates(word)
@@ -1295,12 +1314,16 @@ def analyze(draft: Draft):
             "legend": legend,
         })
 
-    toks_out = [
-        {"l": t["line"], "s": t["start"], "e": t["end"], "g": t["gid"],
-         "end": t["is_end"], "ph": "vowels" in t,
-         "slant": t["slant"] or groups_out[t["gid"]]["slant"]}
-        for t in [*tokens, *phrases] if t["gid"] is not None
-    ]
+    toks_out = []
+    for t in [*tokens, *phrases]:
+        if t["gid"] is None:
+            continue
+        d = {"l": t["line"], "s": t["start"], "e": t["end"], "g": t["gid"],
+             "end": t["is_end"], "ph": "vowels" in t,
+             "slant": t["slant"] or groups_out[t["gid"]]["slant"]}
+        if "vowels" not in t:  # single word: where its rhyming tail starts
+            d["rs"] = t["start"] + rhyme_char_start(t["word"])
+        toks_out.append(d)
     meter, meter_by_line = [], {}
     for i, line in enumerate(lines):
         if sids[i] is None:

static/index.html

@@ -609,7 +609,7 @@ function render(){
       h = esc(line);
     }else{
       const cuts = new Set([0, line.length]);
-      toks.forEach(t=>{ cuts.add(t.s); cuts.add(t.e); });
+      toks.forEach(t=>{ cuts.add(t.s); cuts.add(t.e); if(t.rs != null) cuts.add(t.rs); });
       als.forEach(t=>{ cuts.add(t.s); cuts.add(t.e); });
       opens.forEach(t=>{ cuts.add(t.s); cuts.add(t.e); });
       const pts = [...cuts].sort((a,b)=>a-b);
@@ -622,25 +622,31 @@ function render(){
         const al = als.find(t=>t.s <= a && b <= t.e);
         const op = opens.find(t=>t.s <= a && b <= t.e);
         if(!w && !p && !al && !op){ h += text; continue; }
-        // fills = tail sound (rhyme); underline = head sound (alliteration);
+        // whole word fills dimly; the rhyming part gets a bright underline.
         // gray = an ending still waiting for its answer
         let style = '';
+        const shadows = [];
         if(w || p){
           const t = (w && (focusGid === null || w.g === focusGid)) ? w
                   : (p && (focusGid === null || p.g === focusGid)) ? p
                   : (w || p);
-          let alpha = !t.ph ? (t.end ? 34 : 19) : (t.end ? 24 : 14);
+          let alpha = !t.ph ? (t.end ? 28 : 16) : (t.end ? 20 : 12);
           if(t.slant) alpha = Math.round(alpha * 0.62);  // slant sits back
-          // the caret's family brightens; everything else stays itself
           if(focusGid !== null && t.g === focusGid){
             alpha = Math.min(85, Math.round(alpha * 2.8));
             style += 'color:#1a120c;font-weight:600;';  // dark ink on the lit chip
           }
           style += `background:color-mix(in srgb, ${colorOf(t)} ${alpha}%, transparent);`;
+          // bright underline on the rhyming tail (rs..e) of a word
+          if(w && (w.rs == null || a >= w.rs)){
+            const u = w.slant ? 55 : 80;
+            shadows.push(`inset 0 -2px 0 0 color-mix(in srgb, ${colorOf(w)} ${u}%, transparent)`);
+          }
         }else if(op){
           style += `background:color-mix(in srgb, var(--ink-dim) 13%, transparent);`;
         }
-        if(al) style += `box-shadow:inset 0 -2px 0 0 color-mix(in srgb, var(--r${al.g % COLORS}) 75%, transparent);`;
+        if(al) shadows.push(`inset 0 -2px 0 0 color-mix(in srgb, var(--r${al.g % COLORS}) 75%, transparent)`);
+        if(shadows.length) style += `box-shadow:${shadows.join(',')};`;
         h += `<span class="hseg" style="${style}">${text}</span>`;
       }
     }
@@ -798,11 +804,6 @@ function buildReadout(){
     const bi = st.lines.indexOf(ln);
     if(bi >= 0) parts.unshift(`bar ${bi + 1}/${st.lines.length}`);
   }
-  if(st && st.scheme){
-    const sch = st.scheme.toUpperCase();
-    const shown = sch.slice(0, 16).split('').join(' ') + (sch.length > 16 ? ' …' : '');
-    parts.push(`scheme <b>${shown}</b>`);
-  }
   if(focusGid !== null && analysis){
     const g = analysis.groups.find(x=>x.id === focusGid);
     const fam = [...new Set(analysis.tokens.filter(t=>t.g===focusGid)

tests/test_rhymes.py

@@ -740,3 +740,9 @@ def test_no_matching_across_stanzas():
     # but within each stanza they still rhyme
     assert "night" in s1
     assert any({"bright", "sight"} <= s for s in bg.values())
+
+
+def test_rhyme_char_start():
+    from app import rhyme_char_start
+    assert rhyme_char_start("tonight") == 4   # 'ight'
+    assert rhyme_char_start("write") == 2     # 'ite' (silent-e skipped)