diff --git a/.gitignore b/.gitignore
index 6263750..fe5361d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 .vscode
 *.out
-cover.txt
+cover-test
 cover.html
+cover.txt
diff --git a/Makefile b/Makefile
index 2e93f2f..7c376d2 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,28 @@
+LOCAL_COVER_DIR := cover-test
+
 .PHONY: release
 release:
 	git tag -d v1
 	git tag v1 HEAD
 	git push -f origin v1
+
+$(LOCAL_COVER_DIR)/revisions:
+	@mkdir -p "$(LOCAL_COVER_DIR)/revisions"
+
+$(LOCAL_COVER_DIR)/revisions/local.html: $(LOCAL_COVER_DIR)/revisions
+	@cd go-test-app-01; make test
+	@cd go-test-app-01; go tool cover -html=cover.out -o "../$(LOCAL_COVER_DIR)/revisions/local.html"
+	@cp $(LOCAL_COVER_DIR)/revisions/local.html $(LOCAL_COVER_DIR)/revisions/local-inc.html
+	@for file in assets/*; do ln -s "$$PWD/$$file" "$(LOCAL_COVER_DIR)/$(shell basename "$$file")"; done
+	@cd $(LOCAL_COVER_DIR); REVISION=local ../scripts/beautify-html.sh "$$html_file"
+
+preview: clean $(LOCAL_COVER_DIR)/revisions/local.html
+	@echo ""
+	@echo preview live at: http://localhost:8000?hash=local
+	@echo "  ctrl+c to stop"
+	@echo ""
+	@cd $(LOCAL_COVER_DIR); python3 -m http.server 8000 > /dev/null
+
+clean:
+	@rm -rf "$(LOCAL_COVER_DIR)"
+	@cd go-test-app-01; make clean
diff --git a/assets/index.js b/assets/index.js
index 2850de3..51b7270 100644
--- a/assets/index.js
+++ b/assets/index.js
@@ -34,7 +34,7 @@ function main() {
 
   configureCodeBlocks()
   configureSyntaxHighlight('pre .code .editor')
-  addCoverageSpans('pre .coverage span')
+  addCoverageSpans('pre .coverage .editor')
   addLineNumbers()
 
   // setup complete, restore the page visibility
@@ -42,7 +42,7 @@ function main() {
 }
 
 function addCoverageSpans(cssSelector) {
-  let spans = Array.from(document.querySelectorAll(cssSelector))
+  let spans = Array.from(document.querySelectorAll(`${cssSelector} span`))
 
   spans.forEach((span) => {
     let html = span.innerHTML
diff --git a/scripts/beautify-html.sh b/scripts/beautify-html.sh
new file mode 100755
index 0000000..79e72cf
--- /dev/null
+++ b/scripts/beautify-html.sh
@@ -0,0 +1,24 @@
+#!/bin/bash
+
+if [ "${REVISION}" = "local" ]; then
+  set -eo pipefail
+else
+  set -xeo pipefail
+fi
+
+if [ -z "${REVISION}" ]; then
+  echo "REVISION is not set"
+  exit 1
+fi
+
+# this is useful for browser caching
+hash=$(cat index.css index.js | md5sum | awk '{print $1}')
+
+for file in "revisions/${REVISION}.html" "revisions/${REVISION}-inc.html"; do
+  ex -sc '%s/\n\t\t<style>\_.\{-}<\/style>//' -c 'x' "${file}"
+  ex -sc '%s/\n\t<script>\_.\{-}<\/script>//' -c 'x' "${file}"
+  ex -sc '%s/<title>/<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" \/>\r\t\t<title>/' -c 'x' "${file}"
+  ex -sc '%s/<title>/<meta http-equiv="Pragma" content="no-cache" \/>\r\t\t<title>/' -c 'x' "${file}"
+  ex -sc '%s/<title>/<meta http-equiv="Expires" content="0" \/>\r\t\t<title>/' -c 'x' "${file}"
+  ex -sc '%s/<\/title>/<\/title>\r\t\t<script src="..\/index.js?'"${hash}"'"><\/script>/' -c 'x' "${file}"
+done
diff --git a/scripts/push.sh b/scripts/push.sh
index 0c53b92..93adeaf 100755
--- a/scripts/push.sh
+++ b/scripts/push.sh
@@ -20,6 +20,7 @@ cp cover.out                     "${cover_dir}/revisions/${REVISION}.out"
 
 echo "mode: set" > incremental.out
 # grep exits with 1 if no lines are found, so we need to ignore that
+# incremental = cover - head
 grep -F -v -x -f "${cover_dir}/head/head.out" cover.out >> incremental.out || true
 go tool cover -html=incremental.out -o "${cover_dir}/revisions/${REVISION}-inc.html"
 go tool cover -func=incremental.out -o "${cover_dir}/revisions/${REVISION}-inc.txt"
@@ -27,25 +28,12 @@ cp incremental.out                     "${cover_dir}/revisions/${REVISION}-inc.o
 
 cd "${cover_dir}"
 
-# copy assets
+# prepare assets
 
 cp "${GITHUB_ACTION_PATH}"/assets/* .
+./"${GITHUB_ACTION_PATH}"/scripts/beautify-html.sh
 
-# beautify html
-
-# this is useful for browser caching
-hash=$(cat index.css index.js | md5sum | awk '{print $1}')
-
-for file in "revisions/${REVISION}.html" "revisions/${REVISION}-inc.html"; do
-  ex -sc '%s/\n\t\t<style>\_.\{-}<\/style>//' -c 'x' "${file}"
-  ex -sc '%s/\n\t<script>\_.\{-}<\/script>//' -c 'x' "${file}"
-  ex -sc '%s/<title>/<meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" \/>\r\t\t<title>/' -c 'x' "${file}"
-  ex -sc '%s/<title>/<meta http-equiv="Pragma" content="no-cache" \/>\r\t\t<title>/' -c 'x' "${file}"
-  ex -sc '%s/<title>/<meta http-equiv="Expires" content="0" \/>\r\t\t<title>/' -c 'x' "${file}"
-  ex -sc '%s/<\/title>/<\/title>\r\t\t<script src="..\/index.js?'"${hash}"'"><\/script>/' -c 'x' "${file}"
-done
-
-# if we are on the main branch, copy files to main.*
+# if we are on the main branch, copy files to head.*
 
 if [ "${REF_NAME}" = "main" ]; then
   cp "revisions/${REVISION}.html" "${cover_dir}/head/head.html"