{{- /* Format the displayed specimen only; the live demo keeps its original HTML. */ -}}
{{- $tokens := findRE `(?s)<!--.*?-->|<(?:"[^"]*"|'[^']*'|[^'">])*>|[^<]+` (string .) -}}
{{- $void := slice "area" "base" "br" "col" "embed" "hr" "img" "input" "link" "meta" "param" "source" "track" "wbr" -}}
{{- $lines := slice -}}
{{- $depth := 0 -}}
{{- $skip := -1 -}}
{{- range $i, $raw := $tokens -}}
  {{- if gt $i $skip -}}
    {{- $token := strings.TrimSpace $raw -}}
    {{- if $token -}}
      {{- $line := $token -}}
      {{- $open := gt (len (findRE `^<[A-Za-z]` $token)) 0 -}}
      {{- $leaf := false -}}
      {{- if hasPrefix $token "</" -}}
        {{- $depth = sub $depth 1 -}}
        {{- if lt $depth 0 }}{{ $depth = 0 }}{{ end -}}
      {{- else if $open -}}
        {{- $name := lower (replaceRE `(?s)^<([A-Za-z][A-Za-z0-9:-]*).*` "$1" $token) -}}
        {{- if or (in $void $name) (hasSuffix $token "/>") -}}
          {{- $open = false -}}
        {{- else if lt (add $i 1) (len $tokens) -}}
          {{- $next := index $tokens (add $i 1) -}}
          {{- $close := printf "</%s>" $name -}}
          {{- if eq (lower (strings.TrimSpace $next)) $close -}}
            {{- $line = printf "%s%s" $token (strings.TrimSpace $next) -}}
            {{- $leaf = true -}}
            {{- $skip = add $i 1 -}}
          {{- else if and (not (hasPrefix (strings.TrimSpace $next) "<")) (lt (add $i 2) (len $tokens)) -}}
            {{- $end := strings.TrimSpace (index $tokens (add $i 2)) -}}
            {{- if eq (lower $end) $close -}}
              {{- $line = printf "%s%s%s" $token $next $end -}}
              {{- $leaf = true -}}
              {{- $skip = add $i 2 -}}
            {{- end -}}
          {{- end -}}
        {{- end -}}
      {{- end -}}
      {{- $lines = $lines | append (printf "%*s%s" (mul $depth 2) "" $line) -}}
      {{- if and $open (not $leaf) }}{{ $depth = add $depth 1 }}{{ end -}}
    {{- end -}}
  {{- end -}}
{{- end -}}
{{- return (delimit $lines "\n") -}}