when a money bucket runs out, move spending to another bucket

script.js

@@ -80,17 +80,53 @@ function runProjection(useInflation) {
     roth = roth * growthFactor;
     realEstate = realEstate * growthFactor;
 
-    pretaxSpend = Math.min(pretaxSpend, pretax * (1 - taxRate));
+    var cascadeSpend = 0;
-    pretax -= pretaxSpend / (1 - taxRate);
-    pretax = Math.max(0, pretax);
 
-    aftertaxSpend = Math.min(aftertaxSpend, aftertax);
+    var grossPreTaxSpend = pretaxSpend / (1 - taxRate);
+    if (grossPreTaxSpend > pretax) {
+      cascadeSpend += pretaxSpend - pretax * (1 - taxRate);
+      pretax = 0;
+    } else {
+      pretax -= grossPreTaxSpend;
+      pretax = Math.max(0, pretax);
+    }
+
+    if (aftertaxSpend > aftertax) {
+      cascadeSpend += aftertaxSpend - aftertax;
+      aftertax = 0;
+    } else {
       aftertax -= aftertaxSpend;
       aftertax = Math.max(0, aftertax);
+    }
 
-    rothSpend = Math.min(rothSpend, roth);
+    if (rothSpend > roth) {
+      cascadeSpend += rothSpend - roth;
+      roth = 0;
+    } else {
       roth -= rothSpend;
       roth = Math.max(0, roth);
+    }
+
+    if (cascadeSpend > 0) {
+      var grossCascade = cascadeSpend / (1 - taxRate);
+      if (aftertax > 0) {
+        var aftertaxDraw = Math.min(cascadeSpend, aftertax);
+        aftertax -= aftertaxDraw;
+        aftertax = Math.max(0, aftertax);
+        cascadeSpend -= aftertaxDraw;
+      }
+      if (cascadeSpend > 0 && pretax > 0) {
+        var pretaxDraw = Math.min(cascadeSpend / (1 - taxRate), pretax);
+        pretax -= pretaxDraw;
+        pretax = Math.max(0, pretax);
+        cascadeSpend -= pretaxDraw * (1 - taxRate);
+      }
+      if (cascadeSpend > 0 && roth > 0) {
+        var rothDraw = Math.min(cascadeSpend, roth);
+        roth -= rothDraw;
+        roth = Math.max(0, roth);
+      }
+    }
 
     pretaxSpend *= inflationFactor;
     aftertaxSpend *= inflationFactor;