diff --git a/doc/notes.txt b/doc/notes.txt
index f9bfeddb..fbe89694 100644
--- a/doc/notes.txt
+++ b/doc/notes.txt
@@ -51,6 +51,7 @@ TODO:
 - vscode/atom extension?
 - navigator.getGamepads
 - VCS library
+- better VCS single stepping, maybe also listings
 
 FYI: Image links for the books on http://8bitworkshop.com/ are broken
 On the website the additional grey spacing next to the program line numbers is not dynamically resized when the web browser window size is changed.  Intentional?
diff --git a/presets/vcs/skeleton.dasm b/presets/vcs/skeleton.dasm
index c2be8c5a..60b5248c 100644
--- a/presets/vcs/skeleton.dasm
+++ b/presets/vcs/skeleton.dasm
@@ -24,7 +24,7 @@ Start
 NextFrame
         lsr SWCHB	; test Game Reset switch
         bcc Start	; reset?
-; 3 lines of VSYNC
+; 1 + 3 lines of VSYNC
 	VERTICAL_SYNC
 ; 37 lines of underscan
 	TIMER_SETUP 37
@@ -32,10 +32,10 @@ NextFrame
 ; 192 lines of frame
 	TIMER_SETUP 192
         TIMER_WAIT
-; 30 lines of overscan
-	TIMER_SETUP 30
+; 29 lines of overscan
+	TIMER_SETUP 29
         TIMER_WAIT
-; go to next frame
+; total = 262 lines, go to next frame
         jmp NextFrame
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/src/platform/vcs.ts b/src/platform/vcs.ts
index bd140cc7..6bfe0a44 100644
--- a/src/platform/vcs.ts
+++ b/src/platform/vcs.ts
@@ -1,6 +1,6 @@
 "use strict";
 
-import { Platform, cpuStateToLongString_6502, BaseMAMEPlatform, EmuRecorder, dumpStackToString } from "../baseplatform";
+import { Platform, cpuStateToLongString_6502, BaseMAMEPlatform, EmuRecorder, dumpStackToString, DisasmLine } from "../baseplatform";
 import { PLATFORMS, RAM, newAddressDecoder, dumpRAM } from "../emu";
 import { hex, lpad, tobin, byte2signed } from "../util";
 import { CodeAnalyzer_vcs } from "../analysis";
@@ -116,6 +116,7 @@ class VCSPlatform {
   
   setupDebug(callback) {
     Javatari.room.console.onBreakpointHit = (state) => {
+      state.c.PC = (state.c.PC - 1) & 0xffff;
       Javatari.room.console.pause();
       Javatari.room.speaker.mute();
       callback(state);
@@ -160,7 +161,7 @@ class VCSPlatform {
   }
   runUntilReturn() {
     var depth = 1;
-    this.runEval(function(c) {
+    this.runEval( (c) => {
       if (depth <= 0 && c.T == 0)
         return true;
       if (c.o == 0x20)
@@ -170,6 +171,10 @@ class VCSPlatform {
       return false;
     });
   }
+  runToVsync() {
+    this.advance();
+    this.runEval( (c) => { return true; } );
+  }
   cpuStateToLongString(c) {
     return cpuStateToLongString_6502(c);
   }
@@ -197,7 +202,7 @@ class VCSPlatform {
     }
   }
   piaStateToLongString(p) {
-    return "Timer  " + p.t + "/" + p.c + "\n";
+    return "Timer  " + p.t + "/" + p.c + "\nINTIM  $" + hex(p.IT,2) + " (" + p.IT + ")\nINSTAT $" + hex(p.IS,2) + "\n";
   }
   tiaStateToLongString(t) {
     var pos = this.getRasterPosition();
@@ -237,7 +242,11 @@ class VCSPlatform {
       this.recorder.recordFrame(this.saveState());
     }
   }
+  disassemble(pc:number, read:(addr:number)=>number) : DisasmLine {
+    return disassemble6502(pc, read(pc), read(pc+1), read(pc+2));
+  }
 };
+// TODO: mixin for Base6502Platform?
 
 function nonegstr(n) {
   return n < 0 ? "-" : n.toString();
diff --git a/src/ui.ts b/src/ui.ts
index a3ffb1d3..058970fe 100644
--- a/src/ui.ts
+++ b/src/ui.ts
@@ -706,7 +706,7 @@ function _recordVideo() {
     $("#videoPreviewModal").modal('show');
   });
   var intervalMsec = 17;
-  var maxFrames = 500;
+  var maxFrames = 420;
   var nframes = 0;
   console.log("Recording video", canvas);
   var f = function() {
diff --git a/src/views.ts b/src/views.ts
index 5c53d8f1..d4f59707 100644
--- a/src/views.ts
+++ b/src/views.ts
@@ -512,12 +512,13 @@ export class ListingView extends DisassemblerView implements ProjectView {
       asmtext = asmtext.replace(/[ ]+\d+\s+.area .+\n/g, '');
     }
     disasmview.setValue(asmtext);
-    var findPC = platform.getDebugCallback() ? pc : -1;
+    var debugging = platform.getDebugCallback && platform.getDebugCallback();
+    var findPC = debugging ? pc : -1;
     if (findPC >= 0 && this.assemblyfile) {
       var lineno = this.assemblyfile.findLineForOffset(findPC, 15);
       if (lineno && moveCursor) {
         // set cursor while debugging
-        if (platform.getDebugCallback())
+        if (debugging)
           disasmview.setCursor(lineno-1, 0);
         jumpToLine(disasmview, lineno-1);
       }
diff --git a/src/worker/workermain.js b/src/worker/workermain.js
index 02a275b7..5e36bba2 100644
--- a/src/worker/workermain.js
+++ b/src/worker/workermain.js
@@ -567,6 +567,7 @@ function parseDASMListing(code, unresolved, mainFilename) {
     }
   }
   // TODO: use macrolines
+  // TODO: return {text:code, asmlines:lines, macrolines:macrolines, errors:errors};
   return {lines:lines, macrolines:macrolines, errors:errors};
 }
 
@@ -636,7 +637,6 @@ function assembleDASM(step) {
     listings:listings,
     errors:errors,
     symbolmap:symbolmap,
-    intermediate:{listing:alst, symbols:asym},
   };
 }
 
@@ -806,7 +806,6 @@ function linkLD65(step) {
       listings:listings,
       errors:errors,
       symbolmap:symbolmap,
-      //TODOintermediate:{listing:lstout, map:mapout, symbols:viceout},
     };
   }
 }
@@ -1016,7 +1015,6 @@ function linkSDLDZ80(step)
       listings:listings,
       errors:errors,
       symbolmap:symbolmap,
-      //TODO intermediate:{listing:rstout},
     };
   }
 }