diff --git a/tools/transformer/goldmark/renderer/markdown/LICENSE b/tools/transformer/goldmark/renderer/markdown/LICENSE
deleted file mode 100644
index dc5b2a6..0000000
--- a/tools/transformer/goldmark/renderer/markdown/LICENSE
+++ /dev/null
@@ -1,21 +0,0 @@
-MIT License
-
-Copyright (c) 2019 Yusuke Inuzuka
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
diff --git a/tools/transformer/goldmark/renderer/markdown/block.go b/tools/transformer/goldmark/renderer/markdown/block.go
index 988dc9b..32652f8 100644
--- a/tools/transformer/goldmark/renderer/markdown/block.go
+++ b/tools/transformer/goldmark/renderer/markdown/block.go
@@ -4,39 +4,71 @@ import (
 	"strings"
 
 	"github.com/yuin/goldmark/ast"
+	rendererHTML "github.com/yuin/goldmark/renderer/html"
 	"github.com/yuin/goldmark/util"
 )
 
+func (r *Renderer) renderBlockquote(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	panic("TODO: implement")
+	if entering {
+		if n.Attributes() != nil {
+			_, _ = w.WriteString("<blockquote")
+			rendererHTML.RenderAttributes(w, n, rendererHTML.BlockquoteAttributeFilter)
+			_ = w.WriteByte('>')
+		} else {
+			_, _ = w.WriteString("<blockquote>\n")
+		}
+	} else {
+		_, _ = w.WriteString("</blockquote>\n")
+	}
+	return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderCodeBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	panic("TODO: implement")
+	if entering {
+		_, _ = w.WriteString("<pre><code>")
+		r.writeLines(w, source, n)
+	} else {
+		_, _ = w.WriteString("</code></pre>\n")
+	}
+	return ast.WalkContinue, nil
+}
+
+func (r *Renderer) renderDocument(_ util.BufWriter, _ []byte, _ ast.Node, _ bool) (ast.WalkStatus, error) {
+	return ast.WalkContinue, nil
+}
+
 func (r *Renderer) renderFencedCodeBlock(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	n := node.(*ast.FencedCodeBlock)
 
 	if entering {
-		r.Write(w, "```")
+		r.write(w, "```")
 
 		language := n.Language(source)
 		if language != nil {
-			r.Write(w, language)
+			r.write(w, language)
 		}
 
-		r.Write(w, '\n')
+		r.write(w, '\n')
 		r.writeLines(w, source, n)
 	} else {
-		r.Write(w, "```")
+		r.write(w, "```")
 
 		if r.Config.KillercodaActions {
 			if _, ok := n.AttributeString("data-killercoda-exec"); ok {
-				r.Write(w, "{{exec}}")
+				r.write(w, "{{exec}}")
 			}
 
 			if _, ok := n.AttributeString("data-killercoda-copy"); ok {
-				r.Write(w, "{{copy}}")
+				r.write(w, "{{copy}}")
 			}
 		}
 
-		r.Write(w, '\n')
+		r.write(w, '\n')
 
 		if node.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -47,13 +79,13 @@ func (r *Renderer) renderHeading(w util.BufWriter, _ []byte, node ast.Node, ente
 	n := node.(*ast.Heading)
 
 	if entering {
-		r.Write(w, strings.Repeat("#", n.Level))
-		r.Write(w, ' ')
+		r.write(w, strings.Repeat("#", n.Level))
+		r.write(w, ' ')
 	} else {
-		r.Write(w, '\n')
+		r.write(w, '\n')
 
 		if node.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -64,14 +96,14 @@ func (r *Renderer) renderHTMLBlock(w util.BufWriter, source []byte, node ast.Nod
 	n := node.(*ast.HTMLBlock)
 
 	if entering {
-		r.Write(w, "<!-- raw HTML omitted -->\n")
+		r.write(w, "<!-- raw HTML omitted -->\n")
 	} else {
 		if n.HasClosure() {
-			r.Write(w, "<!-- raw HTML omitted -->\n")
+			r.write(w, "<!-- raw HTML omitted -->\n")
 		}
 
 		if n.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -81,7 +113,7 @@ func (r *Renderer) renderHTMLBlock(w util.BufWriter, source []byte, node ast.Nod
 func (r *Renderer) renderList(w util.BufWriter, _ []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if !entering {
 		if node.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -97,13 +129,13 @@ func (r *Renderer) renderListItem(w util.BufWriter, _ []byte, node ast.Node, ent
 	}
 
 	if entering {
-		r.Write(w, marker)
+		r.write(w, marker)
 		r.indent += indent
 	} else {
 		r.indent -= indent
 
 		if node.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -112,10 +144,10 @@ func (r *Renderer) renderListItem(w util.BufWriter, _ []byte, node ast.Node, ent
 
 func (r *Renderer) renderParagraph(w util.BufWriter, _ []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if !entering {
-		r.Write(w, '\n')
+		r.write(w, '\n')
 
 		if node.NextSibling() != nil {
-			r.Write(w, '\n')
+			r.write(w, '\n')
 		}
 	}
 
@@ -124,8 +156,21 @@ func (r *Renderer) renderParagraph(w util.BufWriter, _ []byte, node ast.Node, en
 
 func (r *Renderer) renderTextBlock(w util.BufWriter, _ []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
 	if !entering {
-		r.Write(w, '\n')
+		r.write(w, '\n')
 	}
 
 	return ast.WalkContinue, nil
 }
+
+func (r *Renderer) renderThematicBreak(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
+	panic("TODO: implement")
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+	_, _ = w.WriteString("<hr")
+	if n.Attributes() != nil {
+		rendererHTML.RenderAttributes(w, n, rendererHTML.ThematicAttributeFilter)
+	}
+	_, _ = w.WriteString(">\n")
+	return ast.WalkContinue, nil
+}
diff --git a/tools/transformer/goldmark/renderer/markdown/goldmark.go b/tools/transformer/goldmark/renderer/markdown/goldmark.go
deleted file mode 100644
index 9b5493a..0000000
--- a/tools/transformer/goldmark/renderer/markdown/goldmark.go
+++ /dev/null
@@ -1,465 +0,0 @@
-// Copyright (c) 2019 Yusuke Inuzuka
-// The MIT license associated with that copyright notice is included in the LICENSE file in this directory.
-package markdown
-
-import (
-	"bytes"
-	"strconv"
-
-	"github.com/yuin/goldmark/ast"
-	"github.com/yuin/goldmark/renderer"
-	"github.com/yuin/goldmark/util"
-)
-
-// RegisterFuncs implements NodeRenderer.RegisterFuncs .
-func (r *Renderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
-	// blocks
-
-	reg.Register(ast.KindDocument, r.renderDocument)
-	reg.Register(ast.KindHeading, r.renderHeading)
-	reg.Register(ast.KindBlockquote, r.renderBlockquote)
-	reg.Register(ast.KindCodeBlock, r.renderCodeBlock)
-	reg.Register(ast.KindFencedCodeBlock, r.renderFencedCodeBlock)
-	reg.Register(ast.KindHTMLBlock, r.renderHTMLBlock)
-	reg.Register(ast.KindList, r.renderList)
-	reg.Register(ast.KindListItem, r.renderListItem)
-	reg.Register(ast.KindParagraph, r.renderParagraph)
-	reg.Register(ast.KindTextBlock, r.renderTextBlock)
-	reg.Register(ast.KindThematicBreak, r.renderThematicBreak)
-
-	// inlines
-
-	reg.Register(ast.KindAutoLink, r.renderAutoLink)
-	reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
-	reg.Register(ast.KindEmphasis, r.renderEmphasis)
-	reg.Register(ast.KindImage, r.renderImage)
-	reg.Register(ast.KindLink, r.renderLink)
-	reg.Register(ast.KindRawHTML, r.renderRawHTML)
-	reg.Register(ast.KindText, r.renderText)
-	reg.Register(ast.KindString, r.renderString)
-}
-
-// GlobalAttributeFilter defines attribute names which any elements can have.
-var GlobalAttributeFilter = util.NewBytesFilter(
-	[]byte("accesskey"),
-	[]byte("autocapitalize"),
-	[]byte("autofocus"),
-	[]byte("class"),
-	[]byte("contenteditable"),
-	[]byte("dir"),
-	[]byte("draggable"),
-	[]byte("enterkeyhint"),
-	[]byte("hidden"),
-	[]byte("id"),
-	[]byte("inert"),
-	[]byte("inputmode"),
-	[]byte("is"),
-	[]byte("itemid"),
-	[]byte("itemprop"),
-	[]byte("itemref"),
-	[]byte("itemscope"),
-	[]byte("itemtype"),
-	[]byte("lang"),
-	[]byte("part"),
-	[]byte("role"),
-	[]byte("slot"),
-	[]byte("spellcheck"),
-	[]byte("style"),
-	[]byte("tabindex"),
-	[]byte("title"),
-	[]byte("translate"),
-)
-
-func (r *Renderer) renderDocument(
-	w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
-	// nothing to do
-	return ast.WalkContinue, nil
-}
-
-// HeadingAttributeFilter defines attribute names which heading elements can have.
-var HeadingAttributeFilter = GlobalAttributeFilter
-
-// BlockquoteAttributeFilter defines attribute names which blockquote elements can have.
-var BlockquoteAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("cite"),
-)
-
-func (r *Renderer) renderBlockquote(
-	w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
-	if entering {
-		if n.Attributes() != nil {
-			_, _ = w.WriteString("<blockquote")
-			RenderAttributes(w, n, BlockquoteAttributeFilter)
-			_ = w.WriteByte('>')
-		} else {
-			_, _ = w.WriteString("<blockquote>\n")
-		}
-	} else {
-		_, _ = w.WriteString("</blockquote>\n")
-	}
-	return ast.WalkContinue, nil
-}
-
-func (r *Renderer) renderCodeBlock(w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
-	if entering {
-		_, _ = w.WriteString("<pre><code>")
-		r.writeLines(w, source, n)
-	} else {
-		_, _ = w.WriteString("</code></pre>\n")
-	}
-	return ast.WalkContinue, nil
-}
-
-// ListAttributeFilter defines attribute names which list elements can have.
-var ListAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("start"),
-	[]byte("reversed"),
-	[]byte("type"),
-)
-
-// ListItemAttributeFilter defines attribute names which list item elements can have.
-var ListItemAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("value"),
-)
-
-// ParagraphAttributeFilter defines attribute names which paragraph elements can have.
-var ParagraphAttributeFilter = GlobalAttributeFilter
-
-// ThematicAttributeFilter defines attribute names which hr elements can have.
-var ThematicAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("align"),   // [Deprecated]
-	[]byte("color"),   // [Not Standardized]
-	[]byte("noshade"), // [Deprecated]
-	[]byte("size"),    // [Deprecated]
-	[]byte("width"),   // [Deprecated]
-)
-
-func (r *Renderer) renderThematicBreak(
-	w util.BufWriter, source []byte, n ast.Node, entering bool) (ast.WalkStatus, error) {
-	if !entering {
-		return ast.WalkContinue, nil
-	}
-	_, _ = w.WriteString("<hr")
-	if n.Attributes() != nil {
-		RenderAttributes(w, n, ThematicAttributeFilter)
-	}
-	_, _ = w.WriteString(">\n")
-	return ast.WalkContinue, nil
-}
-
-// LinkAttributeFilter defines attribute names which link elements can have.
-var LinkAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("download"),
-	// []byte("href"),
-	[]byte("hreflang"),
-	[]byte("media"),
-	[]byte("ping"),
-	[]byte("referrerpolicy"),
-	[]byte("rel"),
-	[]byte("shape"),
-	[]byte("target"),
-)
-
-func (r *Renderer) renderAutoLink(
-	w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
-	n := node.(*ast.AutoLink)
-	if !entering {
-		return ast.WalkContinue, nil
-	}
-	_, _ = w.WriteString(`<a href="`)
-	url := n.URL(source)
-	label := n.Label(source)
-	if n.AutoLinkType == ast.AutoLinkEmail && !bytes.HasPrefix(bytes.ToLower(url), []byte("mailto:")) {
-		_, _ = w.WriteString("mailto:")
-	}
-	_, _ = w.Write(util.EscapeHTML(util.URLEscape(url, false)))
-	if n.Attributes() != nil {
-		_ = w.WriteByte('"')
-		RenderAttributes(w, n, LinkAttributeFilter)
-		_ = w.WriteByte('>')
-	} else {
-		_, _ = w.WriteString(`">`)
-	}
-	_, _ = w.Write(util.EscapeHTML(label))
-	_, _ = w.WriteString(`</a>`)
-	return ast.WalkContinue, nil
-}
-
-// CodeAttributeFilter defines attribute names which code elements can have.
-var CodeAttributeFilter = GlobalAttributeFilter
-
-// EmphasisAttributeFilter defines attribute names which emphasis elements can have.
-var EmphasisAttributeFilter = GlobalAttributeFilter
-
-// ImageAttributeFilter defines attribute names which image elements can have.
-var ImageAttributeFilter = GlobalAttributeFilter.Extend(
-	[]byte("align"),
-	[]byte("border"),
-	[]byte("crossorigin"),
-	[]byte("decoding"),
-	[]byte("height"),
-	[]byte("importance"),
-	[]byte("intrinsicsize"),
-	[]byte("ismap"),
-	[]byte("loading"),
-	[]byte("referrerpolicy"),
-	[]byte("sizes"),
-	[]byte("srcset"),
-	[]byte("usemap"),
-	[]byte("width"),
-)
-
-var dataPrefix = []byte("data-")
-
-// RenderAttributes renders given node's attributes.
-// You can specify attribute names to render by the filter.
-// If filter is nil, RenderAttributes renders all attributes.
-func RenderAttributes(w util.BufWriter, node ast.Node, filter util.BytesFilter) {
-	for _, attr := range node.Attributes() {
-		if filter != nil && !filter.Contains(attr.Name) {
-			if !bytes.HasPrefix(attr.Name, dataPrefix) {
-				continue
-			}
-		}
-		_, _ = w.WriteString(" ")
-		_, _ = w.Write(attr.Name)
-		_, _ = w.WriteString(`="`)
-		// TODO: convert numeric values to strings
-		var value []byte
-		switch typed := attr.Value.(type) {
-		case []byte:
-			value = typed
-		case string:
-			value = util.StringToReadOnlyBytes(typed)
-		}
-		_, _ = w.Write(util.EscapeHTML(value))
-		_ = w.WriteByte('"')
-	}
-}
-
-// A Writer interface writes textual contents to a writer.
-type Writer interface {
-	// Write writes the given source to writer with resolving references and unescaping
-	// backslash escaped characters.
-	Write(writer util.BufWriter, source []byte)
-
-	// RawWrite writes the given source to writer without resolving references and
-	// unescaping backslash escaped characters.
-	RawWrite(writer util.BufWriter, source []byte)
-
-	// SecureWrite writes the given source to writer with replacing insecure characters.
-	SecureWrite(writer util.BufWriter, source []byte)
-}
-
-var replacementCharacter = []byte("\ufffd")
-
-// A WriterConfig struct has configurations for the HTML based writers.
-type WriterConfig struct {
-	// EscapedSpace is an option that indicates that a '\' escaped half-space(0x20) should not be rendered.
-	EscapedSpace bool
-}
-
-// A WriterOption interface sets options for HTML based writers.
-type WriterOption func(*WriterConfig)
-
-// WithEscapedSpace is a WriterOption indicates that a '\' escaped half-space(0x20) should not be rendered.
-func WithEscapedSpace() WriterOption {
-	return func(c *WriterConfig) {
-		c.EscapedSpace = true
-	}
-}
-
-type defaultWriter struct {
-	WriterConfig
-}
-
-// NewWriter returns a new Writer.
-func NewWriter(opts ...WriterOption) Writer {
-	w := &defaultWriter{}
-	for _, opt := range opts {
-		opt(&w.WriterConfig)
-	}
-	return w
-}
-
-func escapeRune(writer util.BufWriter, r rune) {
-	if r < 256 {
-		v := util.EscapeHTMLByte(byte(r))
-		if v != nil {
-			_, _ = writer.Write(v)
-			return
-		}
-	}
-	_, _ = writer.WriteRune(util.ToValidRune(r))
-}
-
-func (d *defaultWriter) SecureWrite(writer util.BufWriter, source []byte) {
-	n := 0
-	l := len(source)
-	for i := 0; i < l; i++ {
-		if source[i] == '\u0000' {
-			_, _ = writer.Write(source[i-n : i])
-			n = 0
-			_, _ = writer.Write(replacementCharacter)
-			continue
-		}
-		n++
-	}
-	if n != 0 {
-		_, _ = writer.Write(source[l-n:])
-	}
-}
-
-func (d *defaultWriter) RawWrite(writer util.BufWriter, source []byte) {
-	n := 0
-	l := len(source)
-	for i := 0; i < l; i++ {
-		v := util.EscapeHTMLByte(source[i])
-		if v != nil {
-			_, _ = writer.Write(source[i-n : i])
-			n = 0
-			_, _ = writer.Write(v)
-			continue
-		}
-		n++
-	}
-	if n != 0 {
-		_, _ = writer.Write(source[l-n:])
-	}
-}
-
-func (d *defaultWriter) Write(writer util.BufWriter, source []byte) {
-	escaped := false
-	var ok bool
-	limit := len(source)
-	n := 0
-	for i := 0; i < limit; i++ {
-		c := source[i]
-		if escaped {
-			if util.IsPunct(c) {
-				d.RawWrite(writer, source[n:i-1])
-				n = i
-				escaped = false
-				continue
-			}
-			if d.EscapedSpace && c == ' ' {
-				d.RawWrite(writer, source[n:i-1])
-				n = i + 1
-				escaped = false
-				continue
-			}
-		}
-		if c == '\x00' {
-			d.RawWrite(writer, source[n:i])
-			d.RawWrite(writer, replacementCharacter)
-			n = i + 1
-			escaped = false
-			continue
-		}
-		if c == '&' {
-			pos := i
-			next := i + 1
-			if next < limit && source[next] == '#' {
-				nnext := next + 1
-				if nnext < limit {
-					nc := source[nnext]
-					// code point like #x22;
-					if nnext < limit && nc == 'x' || nc == 'X' {
-						start := nnext + 1
-						i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsHexDecimal)
-						if ok && i < limit && source[i] == ';' && i-start < 7 {
-							v, _ := strconv.ParseUint(util.BytesToReadOnlyString(source[start:i]), 16, 32)
-							d.RawWrite(writer, source[n:pos])
-							n = i + 1
-							escapeRune(writer, rune(v))
-							continue
-						}
-						// code point like #1234;
-					} else if nc >= '0' && nc <= '9' {
-						start := nnext
-						i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsNumeric)
-						if ok && i < limit && i-start < 8 && source[i] == ';' {
-							v, _ := strconv.ParseUint(util.BytesToReadOnlyString(source[start:i]), 10, 32)
-							d.RawWrite(writer, source[n:pos])
-							n = i + 1
-							escapeRune(writer, rune(v))
-							continue
-						}
-					}
-				}
-			} else {
-				start := next
-				i, ok = util.ReadWhile(source, [2]int{start, limit}, util.IsAlphaNumeric)
-				// entity reference
-				if ok && i < limit && source[i] == ';' {
-					name := util.BytesToReadOnlyString(source[start:i])
-					entity, ok := util.LookUpHTML5EntityByName(name)
-					if ok {
-						d.RawWrite(writer, source[n:pos])
-						n = i + 1
-						d.RawWrite(writer, entity.Characters)
-						continue
-					}
-				}
-			}
-			i = next - 1
-		}
-		if c == '\\' {
-			escaped = true
-			continue
-		}
-		escaped = false
-	}
-	d.RawWrite(writer, source[n:])
-}
-
-// DefaultWriter is a default instance of the Writer.
-var DefaultWriter = NewWriter()
-
-var bDataImage = []byte("data:image/")
-var bPng = []byte("png;")
-var bGif = []byte("gif;")
-var bJpeg = []byte("jpeg;")
-var bWebp = []byte("webp;")
-var bSvg = []byte("svg+xml;")
-var bJs = []byte("javascript:")
-var bVb = []byte("vbscript:")
-var bFile = []byte("file:")
-var bData = []byte("data:")
-
-func hasPrefix(s, prefix []byte) bool {
-	return len(s) >= len(prefix) && bytes.Equal(bytes.ToLower(s[0:len(prefix)]), bytes.ToLower(prefix))
-}
-
-// IsDangerousURL returns true if the given url seems a potentially dangerous url,
-// otherwise false.
-func IsDangerousURL(url []byte) bool {
-	if hasPrefix(url, bDataImage) && len(url) >= 11 {
-		v := url[11:]
-		if hasPrefix(v, bPng) || hasPrefix(v, bGif) ||
-			hasPrefix(v, bJpeg) || hasPrefix(v, bWebp) ||
-			hasPrefix(v, bSvg) {
-			return false
-		}
-		return true
-	}
-	return hasPrefix(url, bJs) || hasPrefix(url, bVb) ||
-		hasPrefix(url, bFile) || hasPrefix(url, bData)
-}
-
-func nodeToHTMLText(n ast.Node, source []byte) []byte {
-	var buf bytes.Buffer
-	for c := n.FirstChild(); c != nil; c = c.NextSibling() {
-		if s, ok := c.(*ast.String); ok && s.IsCode() {
-			buf.Write(s.Text(source))
-		} else if !c.HasChildren() {
-			buf.Write(util.EscapeHTML(c.Text(source)))
-			if t, ok := c.(*ast.Text); ok && t.SoftLineBreak() {
-				buf.WriteByte('\n')
-			}
-		} else {
-			buf.Write(nodeToHTMLText(c, source))
-		}
-	}
-	return buf.Bytes()
-}
diff --git a/tools/transformer/goldmark/renderer/markdown/inline.go b/tools/transformer/goldmark/renderer/markdown/inline.go
index 3ba27bb..6edbcb5 100644
--- a/tools/transformer/goldmark/renderer/markdown/inline.go
+++ b/tools/transformer/goldmark/renderer/markdown/inline.go
@@ -5,29 +5,55 @@ import (
 	"html"
 
 	"github.com/yuin/goldmark/ast"
+	rendererHTML "github.com/yuin/goldmark/renderer/html"
 	"github.com/yuin/goldmark/util"
 )
 
+func (r *Renderer) renderAutoLink(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
+	panic("TODO: implement")
+	n := node.(*ast.AutoLink)
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+	_, _ = w.WriteString(`<a href="`)
+	url := n.URL(source)
+	label := n.Label(source)
+	if n.AutoLinkType == ast.AutoLinkEmail && !bytes.HasPrefix(bytes.ToLower(url), []byte("mailto:")) {
+		_, _ = w.WriteString("mailto:")
+	}
+	_, _ = w.Write(util.EscapeHTML(util.URLEscape(url, false)))
+	if n.Attributes() != nil {
+		_ = w.WriteByte('"')
+		rendererHTML.RenderAttributes(w, n, rendererHTML.LinkAttributeFilter)
+		_ = w.WriteByte('>')
+	} else {
+		_, _ = w.WriteString(`">`)
+	}
+	_, _ = w.Write(util.EscapeHTML(label))
+	_, _ = w.WriteString(`</a>`)
+	return ast.WalkContinue, nil
+}
+
 func (r *Renderer) renderCodeSpan(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if entering {
-		r.Write(w, '`')
+		r.write(w, '`')
 
 		for c := node.FirstChild(); c != nil; c = c.NextSibling() {
 			segment := c.(*ast.Text).Segment
 			value := segment.Value(source)
 
 			if bytes.HasSuffix(value, []byte("\n")) {
-				r.Write(w, value[:len(value)-1])
-				r.Write(w, []byte(" "))
+				r.write(w, value[:len(value)-1])
+				r.write(w, []byte(" "))
 			} else {
-				r.Write(w, value)
+				r.write(w, value)
 			}
 		}
 
 		return ast.WalkSkipChildren, nil
 	}
 
-	r.Write(w, '`')
+	r.write(w, '`')
 
 	return ast.WalkContinue, nil
 }
@@ -41,9 +67,9 @@ func (r *Renderer) renderEmphasis(w util.BufWriter, source []byte, node ast.Node
 	}
 
 	if entering {
-		r.Write(w, delim)
+		r.write(w, delim)
 	} else {
-		r.Write(w, delim)
+		r.write(w, delim)
 	}
 
 	return ast.WalkContinue, nil
@@ -51,19 +77,19 @@ func (r *Renderer) renderEmphasis(w util.BufWriter, source []byte, node ast.Node
 
 func (r *Renderer) renderImage(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
 	if entering {
-		r.Write(w, "![")
+		r.write(w, "![")
 	} else {
 		n := node.(*ast.Image)
 
-		r.Write(w, "](")
-		r.Write(w, n.Destination)
+		r.write(w, "](")
+		r.write(w, n.Destination)
 
 		if n.Title != nil {
-			r.Write(w, " \"")
-			r.Write(w, n.Title)
-			r.Write(w, "\"")
+			r.write(w, " \"")
+			r.write(w, n.Title)
+			r.write(w, "\"")
 		}
-		r.Write(w, ')')
+		r.write(w, ')')
 	}
 
 	return ast.WalkContinue, nil
@@ -73,17 +99,17 @@ func (r *Renderer) renderLink(w util.BufWriter, _ []byte, node ast.Node, enterin
 	n := node.(*ast.Link)
 
 	if entering {
-		r.Write(w, '[')
+		r.write(w, '[')
 	} else {
-		r.Write(w, "](")
-		r.Write(w, n.Destination)
+		r.write(w, "](")
+		r.write(w, n.Destination)
 
 		if n.Title != nil {
-			r.Write(w, " \"")
-			r.Write(w, n.Title)
-			r.Write(w, "\"")
+			r.write(w, " \"")
+			r.write(w, n.Title)
+			r.write(w, "\"")
 		}
-		r.Write(w, ')')
+		r.write(w, ')')
 	}
 
 	return ast.WalkContinue, nil
@@ -94,7 +120,7 @@ func (r *Renderer) renderRawHTML(w util.BufWriter, source []byte, node ast.Node,
 		return ast.WalkSkipChildren, nil
 	}
 
-	r.Write(w, "<!-- raw HTML omitted -->")
+	r.write(w, "<!-- raw HTML omitted -->")
 
 	return ast.WalkSkipChildren, nil
 }
@@ -107,7 +133,7 @@ func (r *Renderer) renderString(w util.BufWriter, _ []byte, node ast.Node, enter
 	n := node.(*ast.String)
 
 	// TODO: understand if there is any risk associated with this.
-	r.Write(w, html.UnescapeString(string(n.Value)))
+	r.write(w, html.UnescapeString(string(n.Value)))
 
 	return ast.WalkContinue, nil
 }
@@ -121,11 +147,11 @@ func (r *Renderer) renderText(w util.BufWriter, source []byte, node ast.Node, en
 	segment := n.Segment
 	value := segment.Value(source)
 
-	r.Write(w, value)
+	r.write(w, value)
 	if n.HardLineBreak() {
-		r.Write(w, "\n\n")
+		r.write(w, "\n\n")
 	} else if n.SoftLineBreak() {
-		r.Write(w, '\n')
+		r.write(w, '\n')
 	}
 
 	return ast.WalkContinue, nil
diff --git a/tools/transformer/goldmark/renderer/markdown/markdown.go b/tools/transformer/goldmark/renderer/markdown/markdown.go
index 70e08ed..2832dda 100644
--- a/tools/transformer/goldmark/renderer/markdown/markdown.go
+++ b/tools/transformer/goldmark/renderer/markdown/markdown.go
@@ -1,6 +1,4 @@
 // Package renderer implements Goldmark renderer that outputs Markdown.
-// This package borrows code from https://github.com/yuin/goldmark/blob/v1.7.2/renderer/html/html.go
-// All borrowed code is in goldmark.go.
 package markdown
 
 import (
@@ -27,8 +25,36 @@ func isNewline(writee any) bool {
 	}
 }
 
+// RegisterFuncs implements NodeRenderer.RegisterFuncs .
+func (r *Renderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	// blocks
+
+	reg.Register(ast.KindDocument, r.renderDocument)
+	reg.Register(ast.KindHeading, r.renderHeading)
+	reg.Register(ast.KindBlockquote, r.renderBlockquote)
+	reg.Register(ast.KindCodeBlock, r.renderCodeBlock)
+	reg.Register(ast.KindFencedCodeBlock, r.renderFencedCodeBlock)
+	reg.Register(ast.KindHTMLBlock, r.renderHTMLBlock)
+	reg.Register(ast.KindList, r.renderList)
+	reg.Register(ast.KindListItem, r.renderListItem)
+	reg.Register(ast.KindParagraph, r.renderParagraph)
+	reg.Register(ast.KindTextBlock, r.renderTextBlock)
+	reg.Register(ast.KindThematicBreak, r.renderThematicBreak)
+
+	// inlines
+
+	reg.Register(ast.KindAutoLink, r.renderAutoLink)
+	reg.Register(ast.KindCodeSpan, r.renderCodeSpan)
+	reg.Register(ast.KindEmphasis, r.renderEmphasis)
+	reg.Register(ast.KindImage, r.renderImage)
+	reg.Register(ast.KindLink, r.renderLink)
+	reg.Register(ast.KindRawHTML, r.renderRawHTML)
+	reg.Register(ast.KindText, r.renderText)
+	reg.Register(ast.KindString, r.renderString)
+}
+
 // TODO: replace with implementation of renderer.Writer interface.
-func (r *Renderer) Write(w util.BufWriter, writee any) {
+func (r *Renderer) write(w util.BufWriter, writee any) {
 	// fmt.Printf("Writing %q with indent %d, previously wrote %q\n", writee, r.indent, r.lastWrittenByte)
 
 	if r.lastWrittenByte == '\n' && !isNewline(writee) {
@@ -63,7 +89,7 @@ func (r *Renderer) Write(w util.BufWriter, writee any) {
 func (r *Renderer) writeLines(w util.BufWriter, source []byte, n ast.Node) {
 	for i := 0; i < n.Lines().Len(); i++ {
 		line := n.Lines().At(i)
-		r.Write(w, line.Value(source))
+		r.write(w, line.Value(source))
 	}
 }
 
diff --git a/tools/transformer/transform.go b/tools/transformer/transform.go
index 19c05fc..067d261 100644
--- a/tools/transformer/transform.go
+++ b/tools/transformer/transform.go
@@ -121,6 +121,32 @@ func (t *ActionTransformer) Transform(node *ast.Document, reader text.Reader, _
 	}
 }
 
+type AdmonitionTransformer struct{}
+
+// Transform implements the parser.ASTTransformer interface and replaces all admonition shortcodes with blockquotes.
+func (t *AdmonitionTransformer) Transform(node *ast.Document, reader text.Reader, _ parser.Context) {
+	source := reader.Source()
+
+	err := ast.Walk(node, func(node ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+
+		if paragraph, ok := node.(*ast.Paragraph); ok {
+			raw := strings.TrimSpace(rawText(paragraph, source))
+
+			if strings.HasPrefix(raw, "{{<") && strings.HasSuffix(raw, ">}}") && strings.Contains(raw, "admonition") {
+				panic("TODO: implement")
+			}
+		}
+
+		return ast.WalkContinue, nil
+	})
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error transforming AST: %v\n", err)
+	}
+}
+
 type FigureTransformer struct{}
 
 // Transform implements the parser.ASTTransformer interface and replaces all figure shortcodes with image elements.
diff --git a/tools/transformer/transform_test.go b/tools/transformer/transform_test.go
index a47ac9a..68b93b4 100644
--- a/tools/transformer/transform_test.go
+++ b/tools/transformer/transform_test.go
@@ -70,6 +70,63 @@ func TestActionTransformer_Transform(t *testing.T) {
 	})
 }
 
+func TestAdmonitionTransformer_Transform(t *testing.T) {
+	t.Parallel()
+
+	t.Run("with {{< syntax in a single paragraph", func(t *testing.T) {
+		t.Parallel()
+
+		b := &bytes.Buffer{}
+		w := bufio.NewWriter(b)
+		md := goldmark.NewMarkdown()
+		md.Parser().AddOptions(parser.WithASTTransformers(util.Prioritized(&AdmonitionTransformer{}, 0)))
+		md.SetRenderer(renderer.NewRenderer(renderer.WithNodeRenderers(util.Prioritized(markdown.NewRenderer(), 1000))))
+
+		src := []byte(`{{< admonition type="note" >}}
+This is a note.
+{{< /admonition >}}
+`)
+
+		root := md.Parser().Parse(text.NewReader(src))
+		require.NoError(t, md.Renderer().Render(w, src, root))
+
+		w.Flush()
+
+		want := `> **Note:**
+> This is a note.
+`
+
+		assert.Equal(t, want, b.String())
+	})
+	t.Run("with {{< syntax over multiple paragraphs", func(t *testing.T) {
+		t.Parallel()
+
+		b := &bytes.Buffer{}
+		w := bufio.NewWriter(b)
+		md := goldmark.NewMarkdown()
+		md.Parser().AddOptions(parser.WithASTTransformers(util.Prioritized(&AdmonitionTransformer{}, 0)))
+		md.SetRenderer(renderer.NewRenderer(renderer.WithNodeRenderers(util.Prioritized(markdown.NewRenderer(), 1000))))
+
+		src := []byte(`{{< admonition type="note" >}}
+
+This is a note.
+
+{{< /admonition >}}
+`)
+
+		root := md.Parser().Parse(text.NewReader(src))
+		require.NoError(t, md.Renderer().Render(w, src, root))
+
+		w.Flush()
+
+		want := `> **Note:**
+> This is a note.
+`
+
+		assert.Equal(t, want, b.String())
+	})
+}
+
 func TestFigureTransformer_Transform(t *testing.T) {
 	t.Parallel()