diff --git a/100.txt b/100.txt
new file mode 100644
index 00000000..076b9919
--- /dev/null
+++ b/100.txt
@@ -0,0 +1,11 @@
+We're now past C++ bootstrap.
+
+Layers in the 1xx series are in bare SubX, without any syntax sugar. They are
+intended to be used by the phases of the self-hosted translator to replicate
+the functionality of the C++ bootstrap:
+  apps/hex.subx
+  apps/survey.subx
+  apps/pack.subx
+  apps/dquotes.subx
+  apps/assort.subx
+  apps/tests.subx
diff --git a/050_write.subx b/101_write.subx
similarity index 100%
rename from 050_write.subx
rename to 101_write.subx
diff --git a/051test.subx b/102test.subx
similarity index 100%
rename from 051test.subx
rename to 102test.subx
diff --git a/052kernel-string-equal.subx b/103kernel-string-equal.subx
similarity index 100%
rename from 052kernel-string-equal.subx
rename to 103kernel-string-equal.subx
diff --git a/053new-segment.subx b/104new-segment.subx
similarity index 100%
rename from 053new-segment.subx
rename to 104new-segment.subx
diff --git a/054string-equal.subx b/105string-equal.subx
similarity index 100%
rename from 054string-equal.subx
rename to 105string-equal.subx
diff --git a/055stream.subx b/106stream.subx
similarity index 100%
rename from 055stream.subx
rename to 106stream.subx
diff --git a/056trace.subx b/107trace.subx
similarity index 100%
rename from 056trace.subx
rename to 107trace.subx
diff --git a/057write.subx b/108write.subx
similarity index 100%
rename from 057write.subx
rename to 108write.subx
diff --git a/058stream-equal.subx b/109stream-equal.subx
similarity index 100%
rename from 058stream-equal.subx
rename to 109stream-equal.subx
diff --git a/059stop.subx b/110stop.subx
similarity index 100%
rename from 059stop.subx
rename to 110stop.subx
diff --git a/060read.subx b/111read.subx
similarity index 100%
rename from 060read.subx
rename to 111read.subx
diff --git a/061read-byte.subx b/112read-byte.subx
similarity index 100%
rename from 061read-byte.subx
rename to 112read-byte.subx
diff --git a/062write-stream.subx b/113write-stream.subx
similarity index 100%
rename from 062write-stream.subx
rename to 113write-stream.subx
diff --git a/063error.subx b/114error.subx
similarity index 100%
rename from 063error.subx
rename to 114error.subx
diff --git a/064write-byte.subx b/115write-byte.subx
similarity index 100%
rename from 064write-byte.subx
rename to 115write-byte.subx
diff --git a/065write-buffered.subx b/116write-buffered.subx
similarity index 100%
rename from 065write-buffered.subx
rename to 116write-buffered.subx
diff --git a/066write-int-hex.subx b/117write-int-hex.subx
similarity index 100%
rename from 066write-int-hex.subx
rename to 117write-int-hex.subx
diff --git a/067parse-hex.subx b/118parse-hex.subx
similarity index 100%
rename from 067parse-hex.subx
rename to 118parse-hex.subx
diff --git a/068error-byte.subx b/119error-byte.subx
similarity index 100%
rename from 068error-byte.subx
rename to 119error-byte.subx
diff --git a/069allocate.subx b/120allocate.subx
similarity index 100%
rename from 069allocate.subx
rename to 120allocate.subx
diff --git a/070new-stream.subx b/121new-stream.subx
similarity index 100%
rename from 070new-stream.subx
rename to 121new-stream.subx
diff --git a/071read-line.subx b/122read-line.subx
similarity index 100%
rename from 071read-line.subx
rename to 122read-line.subx
diff --git a/072slice.subx b/123slice.subx
similarity index 100%
rename from 072slice.subx
rename to 123slice.subx
diff --git a/073next-token.subx b/124next-token.subx
similarity index 100%
rename from 073next-token.subx
rename to 124next-token.subx
diff --git a/074write-stream-data.subx b/125write-stream-data.subx
similarity index 100%
rename from 074write-stream-data.subx
rename to 125write-stream-data.subx
diff --git a/075write-int-decimal.subx b/126write-int-decimal.subx
similarity index 100%
rename from 075write-int-decimal.subx
rename to 126write-int-decimal.subx
diff --git a/076next-word.subx b/127next-word.subx
similarity index 100%
rename from 076next-word.subx
rename to 127next-word.subx
diff --git a/077subx-words.subx b/128subx-words.subx
similarity index 100%
rename from 077subx-words.subx
rename to 128subx-words.subx
diff --git a/078emit-hex.subx b/129emit-hex.subx
similarity index 100%
rename from 078emit-hex.subx
rename to 129emit-hex.subx
diff --git a/079emit.subx b/130emit.subx
similarity index 100%
rename from 079emit.subx
rename to 130emit.subx
diff --git a/081table.subx b/131table.subx
similarity index 100%
rename from 081table.subx
rename to 131table.subx
diff --git a/082slurp.subx b/132slurp.subx
similarity index 100%
rename from 082slurp.subx
rename to 132slurp.subx
diff --git a/083subx-widths.subx b/133subx-widths.subx
similarity index 100%
rename from 083subx-widths.subx
rename to 133subx-widths.subx
diff --git a/084emit-hex-array.subx b/134emit-hex-array.subx
similarity index 100%
rename from 084emit-hex-array.subx
rename to 134emit-hex-array.subx
diff --git a/085next-word-or-string.subx b/135next-word-or-string.subx
similarity index 100%
rename from 085next-word-or-string.subx
rename to 135next-word-or-string.subx
diff --git a/200.txt b/200.txt
new file mode 100644
index 00000000..5dd57840
--- /dev/null
+++ b/200.txt
@@ -0,0 +1,5 @@
+Layers in the 2xx series are in bare SubX, without any syntax sugar. They are
+intended to be used by various syntax-sugar phases:
+  apps/sigils.subx
+  apps/calls.subx
+  apps/braces.subx
diff --git a/090register-names.subx b/201register-names.subx
similarity index 100%
rename from 090register-names.subx
rename to 201register-names.subx
diff --git a/091write-int.subx b/202write-int.subx
similarity index 100%
rename from 091write-int.subx
rename to 202write-int.subx
diff --git a/092stack.subx b/203stack.subx
similarity index 100%
rename from 092stack.subx
rename to 203stack.subx
diff --git a/300.txt b/300.txt
new file mode 100644
index 00000000..1544081b
--- /dev/null
+++ b/300.txt
@@ -0,0 +1,3 @@
+Layers in the 3xx series use all the available syntax sugar for SubX programs.
+For the most part they're intended to be used by the Mu translator:
+  apps/mu.subx
diff --git a/100array-equal.subx b/301array-equal.subx
similarity index 100%
rename from 100array-equal.subx
rename to 301array-equal.subx
diff --git a/101stack_allocate.subx b/302stack_allocate.subx
similarity index 100%
rename from 101stack_allocate.subx
rename to 302stack_allocate.subx
diff --git a/102kernel-string.subx b/303kernel-string.subx
similarity index 100%
rename from 102kernel-string.subx
rename to 303kernel-string.subx
diff --git a/103screen.subx b/304screen.subx
similarity index 100%
rename from 103screen.subx
rename to 304screen.subx
diff --git a/104keyboard.subx b/305keyboard.subx
similarity index 100%
rename from 104keyboard.subx
rename to 305keyboard.subx
diff --git a/105files.subx b/306files.subx
similarity index 100%
rename from 105files.subx
rename to 306files.subx
diff --git a/106size.subx b/307size.subx
similarity index 100%
rename from 106size.subx
rename to 307size.subx
diff --git a/test_apps b/test_apps
index 3552971b..325266e1 100755
--- a/test_apps
+++ b/test_apps
@@ -185,7 +185,7 @@ test $NATIVE  &&  {
 # Larger apps that use the standard library.
 
 echo factorial
-./bootstrap translate init.$OS 0[0-8]*.subx apps/factorial.subx  -o apps/factorial
+./bootstrap translate init.$OS [01]*.subx apps/factorial.subx  -o apps/factorial
 test "$1" = 'record'  ||  git diff --exit-code apps/factorial
 test $EMULATED  &&  {
   ./bootstrap run apps/factorial  ||  ret=$?
@@ -201,7 +201,7 @@ test $NATIVE  &&  {
 }
 
 echo crenshaw2-1
-./bootstrap translate init.$OS 0[0-8]*.subx apps/crenshaw2-1.subx  -o apps/crenshaw2-1
+./bootstrap translate init.$OS [01]*.subx apps/crenshaw2-1.subx  -o apps/crenshaw2-1
 test "$1" = 'record'  ||  git diff --exit-code apps/crenshaw2-1
 test $EMULATED  &&  {
   ./bootstrap run apps/crenshaw2-1 test
@@ -213,7 +213,7 @@ test $NATIVE  &&  {
 }
 
 echo crenshaw2-1b
-./bootstrap translate init.$OS 0[0-8]*.subx apps/crenshaw2-1b.subx  -o apps/crenshaw2-1b
+./bootstrap translate init.$OS [01]*.subx apps/crenshaw2-1b.subx  -o apps/crenshaw2-1b
 test "$1" = 'record'  ||  git diff --exit-code apps/crenshaw2-1b
 test $EMULATED  &&  {
   ./bootstrap run apps/crenshaw2-1b test
@@ -229,7 +229,7 @@ test $NATIVE  &&  {
 for phase in hex survey pack assort dquotes tests
 do
   echo $phase
-  ./bootstrap translate init.$OS 0[0-8]*.subx apps/subx-params.subx apps/$phase.subx -o apps/$phase
+  ./bootstrap translate init.$OS [01]*.subx apps/subx-params.subx apps/$phase.subx -o apps/$phase
   test "$1" = 'record'  ||  git diff --exit-code apps/$phase
   test $EMULATED  &&  {
     ./bootstrap run apps/$phase test
@@ -247,7 +247,7 @@ done
 # to go beyond functionality of the C++ bootstrap.
 
 echo sigils
-./bootstrap translate init.$OS 0*.subx apps/subx-params.subx apps/sigils.subx  -o apps/sigils
+./bootstrap translate init.$OS [012]*.subx apps/subx-params.subx apps/sigils.subx  -o apps/sigils
 test "$1" = 'record'  ||  git diff --exit-code apps/sigils
 test $EMULATED  &&  {
   ./bootstrap run apps/sigils test
@@ -261,7 +261,7 @@ test $NATIVE  &&  {
 test $NATIVE  ||  { echo 'there are more tests, but you need Linux to run them'; exit 0; }
 
 echo calls
-cat init.$OS 0*.subx apps/subx-params.subx apps/calls.subx  |  apps/sigils  > a.sigils
+cat init.$OS [012]*.subx apps/subx-params.subx apps/calls.subx  |  apps/sigils  > a.sigils
 ./bootstrap translate a.sigils -o apps/calls
 test "$1" = 'record'  ||  git diff --exit-code apps/calls
 test $EMULATED  &&  {
@@ -274,7 +274,7 @@ test $NATIVE  &&  {
 }
 
 echo braces
-cat init.$OS 0*.subx apps/subx-params.subx apps/braces.subx  |  apps/calls  |  apps/sigils  > a.sigils
+cat init.$OS [012]*.subx apps/subx-params.subx apps/braces.subx  |  apps/calls  |  apps/sigils  > a.sigils
 ./bootstrap translate a.sigils -o apps/braces
 test "$1" = 'record'  ||  git diff --exit-code apps/braces
 test $EMULATED  &&  {
@@ -316,7 +316,7 @@ done
 for app in factorial crenshaw2-1 crenshaw2-1b
 do
   echo $app
-  ./translate_subx init.$OS 0[0-8]*.subx apps/$app.subx
+  ./translate_subx init.$OS [01]*.subx apps/$app.subx
   diff apps/$app a.elf
 done
 
@@ -325,14 +325,14 @@ done
 for app in hex survey pack assort dquotes tests
 do
   echo $app
-  ./translate_subx init.$OS 0[0-8]*.subx apps/subx-params.subx apps/$app.subx
+  ./translate_subx init.$OS [01]*.subx apps/subx-params.subx apps/$app.subx
   diff apps/$app a.elf
 done
 
 for app in sigils calls braces
 do
   echo $app
-  ./translate_subx init.$OS 0*.subx apps/subx-params.subx apps/$app.subx
+  ./translate_subx init.$OS [012]*.subx apps/subx-params.subx apps/$app.subx
   diff apps/$app a.elf
 done