diff --git a/http/fs/fs.go b/http/fs/fs.go
new file mode 100644
index 0000000..7a04e72
--- /dev/null
+++ b/http/fs/fs.go
@@ -0,0 +1,121 @@
+package fs
+
+import (
+	"io/fs"
+	"net/http"
+	"os"
+	"path"
+	"strings"
+	"time"
+)
+
+// -----------------------------------------------------------------------------------------
+
+type unionFS struct {
+	fs []http.FileSystem
+}
+
+func (p *unionFS) Open(name string) (f http.File, err error) {
+	for _, fs := range p.fs {
+		f, err = fs.Open(name)
+		if !os.IsNotExist(err) {
+			return
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+func Union(fs ...http.FileSystem) http.FileSystem {
+	return &unionFS{fs}
+}
+
+// -----------------------------------------------------------------------------------------
+
+type filesFS struct {
+	files []string
+}
+
+func (p *filesFS) Open(name string) (f http.File, err error) {
+	files := p.files
+	name = name[1:]
+	for i := 0; i < len(files); i += 2 {
+		if files[i] == name {
+			f, err = os.Open(files[i+1])
+			return
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+func Files(files ...string) http.FileSystem {
+	return &filesFS{files}
+}
+
+// -----------------------------------------------------------------------------------------
+
+type filesDataFS struct {
+	files []string
+}
+
+type dataFileInfo struct {
+	r    *strings.Reader
+	name string
+}
+
+func (p *dataFileInfo) Name() string {
+	return path.Base(p.name)
+}
+
+func (p *dataFileInfo) Size() int64 {
+	return p.r.Size()
+}
+
+func (p *dataFileInfo) Mode() fs.FileMode {
+	return 0
+}
+
+func (p *dataFileInfo) ModTime() time.Time {
+	return time.Now()
+}
+
+func (p *dataFileInfo) IsDir() bool {
+	return false
+}
+
+func (p *dataFileInfo) Sys() interface{} {
+	return nil
+}
+
+type dataFile struct {
+	*strings.Reader
+	name string
+}
+
+func (p *dataFile) Close() error {
+	return nil
+}
+
+func (p *dataFile) Readdir(count int) ([]fs.FileInfo, error) {
+	return nil, nil
+}
+
+func (p *dataFile) Stat() (fs.FileInfo, error) {
+	return &dataFileInfo{p.Reader, p.name}, nil
+}
+
+func (p *filesDataFS) Open(name string) (f http.File, err error) {
+	files := p.files
+	name = name[1:]
+	for i := 0; i < len(files); i += 2 {
+		if files[i] == name {
+			return &dataFile{strings.NewReader(files[i+1]), name}, nil
+		}
+	}
+	return nil, os.ErrNotExist
+}
+
+func FilesWithContent(files ...string) http.FileSystem {
+	return &filesDataFS{files}
+}
+
+// -----------------------------------------------------------------------------------------
diff --git a/http/nocache/nocache.go b/http/nocache/nocache.go
new file mode 100644
index 0000000..c780e28
--- /dev/null
+++ b/http/nocache/nocache.go
@@ -0,0 +1,21 @@
+package nocache
+
+import (
+	"net/http"
+)
+
+type respWriter struct {
+	http.ResponseWriter
+}
+
+func (p *respWriter) WriteHeader(statusCode int) {
+	w := p.ResponseWriter
+	w.Header().Del("Last-Modified")
+	w.WriteHeader(statusCode)
+}
+
+func New(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		h.ServeHTTP(&respWriter{w}, r)
+	})
+}
diff --git a/http/tracer/tracer.go b/http/tracer/tracer.go
new file mode 100644
index 0000000..3586502
--- /dev/null
+++ b/http/tracer/tracer.go
@@ -0,0 +1,13 @@
+package tracer
+
+import (
+	"log"
+	"net/http"
+)
+
+func New(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("%s %v\n", r.Method, r.URL)
+		h.ServeHTTP(w, r)
+	})
+}
diff --git a/shell/open.go b/shell/open.go
new file mode 100644
index 0000000..43e16e5
--- /dev/null
+++ b/shell/open.go
@@ -0,0 +1,25 @@
+package shell
+
+import (
+	"os/exec"
+	"runtime"
+)
+
+// Open opens the specified URL in the default browser of the user.
+// See https://stackoverflow.com/questions/39320371/how-start-web-server-to-open-page-in-browser-in-golang
+func Open(url string) error {
+	var cmd string
+	var args []string
+
+	switch runtime.GOOS {
+	case "windows":
+		cmd = "cmd"
+		args = []string{"/c", "start"}
+	case "darwin":
+		cmd = "open"
+	default: // "linux", "freebsd", "openbsd", "netbsd"
+		cmd = "xdg-open"
+	}
+	args = append(args, url)
+	return exec.Command(cmd, args...).Start()
+}