diff --git a/index.html b/index.html
index 60f7d85e..ddf95771 100644
--- a/index.html
+++ b/index.html
@@ -244,7 +244,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
   <!--<script async src="//platform.twitter.com/widgets.js" charset="utf-8"></script>-->
 <!--</div>-->
 <div id="pleaseWaitModal" class="modal fade">
-  <div class="modal-dialog modal-lg" role="document">
+  <div class="modal-dialog modal-md" role="document">
     <div class="modal-content">
       <div class="modal-body">
         Please wait...
@@ -257,7 +257,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
   </div>
 </div>
 <div id="videoPreviewModal" class="modal fade">
-  <div class="modal-dialog modal-lg" role="document">
+  <div class="modal-dialog modal-md" role="document">
     <div class="modal-content">
       <div class="modal-header">
         <h3 class="modal-title">Video Preview - Right-click to save</h3>
@@ -294,8 +294,27 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
     </div>
   </div>
 </div>
+<div id="debugExprModal" class="modal fade">
+  <div class="modal-dialog modal-md" role="document">
+    <div class="modal-content">
+      <div class="modal-header">
+        <h3 class="modal-title">Break Expression</h3>
+      </div>
+      <div class="modal-body">
+        <p>Enter a break expression:</p>
+        <p><input id="debugExprInput" size="60"></input></p>
+        <p>Examples:</p>
+        <pre id="debugExprExamples"></pre>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-primary" id="debugExprSubmit">Debug</button>
+        <button type="button" class="btn btn-secondary" data-dismiss="modal">Cancel</button>
+      </div>
+    </div>
+  </div>
+</div>
 <div id="importGithubModal" class="modal fade">
-  <div class="modal-dialog modal-lg" role="document">
+  <div class="modal-dialog modal-md" role="document">
     <div class="modal-content">
       <div class="modal-header">
         <h3 class="modal-title">Import Project from GitHub</h3>
@@ -313,7 +332,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
   </div>
 </div>
 <div id="publishGithubModal" class="modal fade">
-  <div class="modal-dialog modal-lg" role="document">
+  <div class="modal-dialog modal-md" role="document">
     <div class="modal-content">
       <div class="modal-header">
         <h3 class="modal-title">Publish Project on GitHub</h3>
@@ -344,7 +363,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
   </div>
 </div>
 <div id="pushGithubModal" class="modal fade">
-  <div class="modal-dialog modal-lg" role="document">
+  <div class="modal-dialog modal-md" role="document">
     <div class="modal-content">
       <div class="modal-header">
         <h3 class="modal-title">Push Project Changes to GitHub</h3>
diff --git a/src/ui.ts b/src/ui.ts
index fd6bd675..cdbf1890 100644
--- a/src/ui.ts
+++ b/src/ui.ts
@@ -1070,15 +1070,36 @@ function resetAndDebug() {
 }
 
 function _breakExpression() {
-  console.log(platform.saveState());
-  // TODO: better
-  var exprs = window.prompt("Enter break expression", lastBreakExpr);
-  if (exprs) {
-    var fn = new Function('c', 'return (' + exprs + ');').bind(platform);
-    setupBreakpoint();
-    platform.runEval(fn as DebugEvalCondition);
-    lastBreakExpr = exprs;
-  }
+  var modal = $("#debugExprModal");
+  var btn = $("#debugExprSubmit");
+  $("#debugExprInput").val(lastBreakExpr);
+  $("#debugExprExamples").text(getDebugExprExamples());
+  modal.modal('show');
+  btn.off('click').on('click', () => {
+    var exprs = $("#debugExprInput").val()+"";
+    modal.modal('hide');
+    breakExpression(exprs);
+  });
+}
+
+function getDebugExprExamples() : string {
+  var state = platform.saveState && platform.saveState();
+  var cpu = platform.getCPUState && platform.getCPUState();
+  console.log(cpu, state);
+  var s = '';
+  if (cpu.PC) s += "c.PC == 0x" + hex(cpu.PC) + "\n";
+  if (cpu.SP) s += "c.SP < 0x" + hex(cpu.SP) + "\n";
+  if (platform.readAddress) s += "this.readAddress(0x1234) == 0x0\n";
+  if (platform.readVRAMAddress) s += "this.readVRAMAddress(0x1234) != 0x80\n";
+  if (platform.getRasterPosition) s += "this.getRasterPosition().y > 222\n";
+  return s;
+}
+
+function breakExpression(exprs : string) {
+  var fn = new Function('c', 'return (' + exprs + ');').bind(platform);
+  setupBreakpoint();
+  platform.runEval(fn as DebugEvalCondition);
+  lastBreakExpr = exprs;
 }
 
 function getSymbolAtAddress(a : number) {