diff --git a/player-asbuilt.html b/player-asbuilt.html
index d8d20f0..61e560d 100644
--- a/player-asbuilt.html
+++ b/player-asbuilt.html
@@ -11,8 +11,9 @@
     • a 128×64 MONOCHROME OLED (SSD1306/SH1106 class): rendered as a true 1-bit
       framebuffer (drawn, then thresholded to crisp on/off pixels, scaled with
       image-rendering:pixelated) so the cramped real layout is honest;
-    • a fixed 16-pixel WS2812 ("NeoPixel") RGB beat bar (PIO-driven) — lights the
-      first beatsPerBar slots, cyan downbeats / amber group-starts / dim others;
+    • a 4×16 WS2812 ("NeoPixel") RGB matrix (PIO-driven): the bottom row is the
+      beat (cyan downbeats / amber group-starts), and the three rows above stack
+      the current beat's subdivisions as they pass (driven by the finest lane);
     • an EC11 rotary encoder (turn it: wheel or drag) for tempo, tactile buttons,
       a MAX98357A-style speaker, USB-C and a PWR LED in a matte 3D-printed case.
   Compare with the idealized /player.html. One file, no deps; shares src/engine.js.
@@ -86,13 +87,15 @@
     background:#000; border-radius:2px }
   .oled-cap{ text-align:center; font-size:10px; color:var(--muted); margin-top:6px; letter-spacing:.02em }
 
-  /* ---- WS2812 RGB beat bar (fixed 16 px) ---- */
-  .ledbar{ display:flex; gap:5px; justify-content:center; align-items:center; margin:16px auto 4px; width:max-content;
-    background:linear-gradient(180deg,#10221c,var(--pcb)); border:1px solid #07140f; border-radius:5px; padding:7px 9px;
+  /* ---- 4×16 WS2812 RGB matrix: bottom row = beat, 3 rows above = subdivisions ---- */
+  .ledgrid{ display:flex; flex-direction:column; gap:5px; width:max-content; margin:16px auto 4px;
+    background:linear-gradient(180deg,#10221c,var(--pcb)); border:1px solid #07140f; border-radius:5px; padding:8px 9px;
     box-shadow:inset 0 1px 2px rgba(0,0,0,.6) }
-  .npx{ width:16px; height:16px; border-radius:3px; background:#0c0e10; border:1px solid #05measure;
-    border:1px solid #060708; position:relative; transition:background .05s, box-shadow .05s }
-  .npx::after{ content:""; position:absolute; inset:4px; border-radius:1px; background:rgba(255,255,255,.06) }  /* the 5050 die */
+  .ledrow{ display:flex; gap:5px }
+  .ledrow.beatrow{ margin-top:4px; padding-top:6px; border-top:1px solid rgba(255,255,255,.07) }
+  .npx{ width:15px; height:15px; border-radius:3px; background:#0c0e10; border:1px solid #060708;
+    position:relative; transition:background .05s, box-shadow .05s }
+  .npx::after{ content:""; position:absolute; inset:4px; border-radius:1px; background:rgba(255,255,255,.05) }  /* the 5050 die */
   .ledbar-cap{ text-align:center; font-size:10px; color:var(--muted); margin:2px 0 0; letter-spacing:.02em }
 
   /* ---- controls: encoder + tactile buttons ---- */
@@ -165,8 +168,8 @@
   </div>
   <div class="oled-cap">0.96″ 128×64 mono OLED (SSD1306)</div>
 
-  <div class="ledbar" id="leds"></div>
-  <div class="ledbar-cap">16‑px WS2812 RGB beat bar</div>
+  <div class="ledgrid" id="leds"></div>
+  <div class="ledbar-cap">4×16 WS2812 — beat (bottom) + 3 subdivision rows</div>
 
   <div class="controls">
     <div class="keys">
@@ -320,19 +323,36 @@ function drawOLED(){
   oledThreshold();
 }
 
-/* ========================= RENDER: 16-px WS2812 beat bar ===================== */
-const LED_COUNT=16, CYAN="#0AB3F7", AMBER="#ffd166";
-function buildBar(){ const box=$("leds"); box.innerHTML=""; for(let i=0;i<LED_COUNT;i++){ const d=document.createElement("div"); d.className="npx"; box.appendChild(d); } }
+/* ========== RENDER: 4×16 WS2812 matrix — beat row + 3 subdivision rows ========= */
+const LED_COLS=16, LED_ROWS=4, CYAN="#0AB3F7", AMBER="#ffd166", SUB="#2fe0a0";
+let gridLeds=[];
+function buildBar(){
+  const box=$("leds"); box.innerHTML=""; gridLeds=[[],[],[],[]];
+  for(let r=LED_ROWS-1;r>=0;r--){                          // top row built first → the beat row (r=0) sits at the bottom
+    const row=document.createElement("div"); row.className="ledrow"+(r===0?" beatrow":"");
+    for(let c=0;c<LED_COLS;c++){ const d=document.createElement("div"); d.className="npx"; row.appendChild(d); gridLeds[r][c]=d; }
+    box.appendChild(row);
+  }
+}
+function setPx(led,bg,sh){ led.style.background=bg; led.style.boxShadow=sh||"none"; }
 function renderBar(){
-  const m=meters[0], bpb=m?m.beatsPerBar:0;
-  const cur=(state.running&&m)? Math.floor(m.currentStep/m.stepsPerBeat) : -1;
-  const els=$("leds").children;
-  for(let i=0;i<els.length;i++){
-    const led=els[i];
-    if(i>=bpb){ led.style.background="#0c0e10"; led.style.boxShadow="none"; continue; }   // unused pixel on the fixed strip
-    const grp=m.groupStarts.has(i);
-    if(i===cur){ const c=grp?AMBER:CYAN; led.style.background=c; led.style.boxShadow="0 0 10px "+c+", inset 0 0 4px #fff"; }
-    else { led.style.background = grp?"rgba(255,209,102,.30)":"rgba(10,179,247,.20)"; led.style.boxShadow="none"; }
+  const ref=meters[0], bpb=ref?ref.beatsPerBar:0;
+  // beats come from lane 1; subdivisions from the finest lane sharing that beat grid
+  let disp=ref; if(ref){ for(const m of meters){ if(!m.poly && m.beatsPerBar===ref.beatsPerBar && m.stepsPerBeat>disp.stepsPerBeat) disp=m; } }
+  const spb=disp?disp.stepsPerBeat:1;
+  let curBeat=-1, curSub=-1;
+  if(state.running&&disp&&disp.currentStep>=0){ curBeat=Math.floor(disp.currentStep/spb); curSub=disp.currentStep%spb; }
+  for(let r=0;r<LED_ROWS;r++) for(let c=0;c<LED_COLS;c++){
+    const led=gridLeds[r][c];
+    if(c>=bpb){ setPx(led,"#0c0e10"); continue; }          // unused column on the fixed matrix
+    const grp=ref.groupStarts.has(c);
+    if(r===0){                                              // BEAT row (bottom)
+      if(c===curBeat){ const col=grp?AMBER:CYAN; setPx(led,col,"0 0 9px "+col+", inset 0 0 3px #fff"); }
+      else setPx(led, grp?"rgba(255,209,102,.26)":"rgba(10,179,247,.15)");
+    } else if(r<spb && c===curBeat){                        // SUBDIVISION rows — climb in the current beat's column
+      if(curSub>=r) setPx(led,SUB,"0 0 7px "+SUB);          // reached this subdivision
+      else setPx(led,"rgba(47,224,160,.10)");               // ahead: faint slot showing the ladder this beat will climb
+    } else setPx(led,"#0c0e10");                            // off (no such subdivision, or not the current beat)
   }
 }