diff --git a/document.cpp b/document.cpp
index b55fb1e2c1..8ba707d34c 100644
--- a/document.cpp
+++ b/document.cpp
@@ -2,6 +2,7 @@
 #include "node.h"
 #include "parser.h"
 #include "scanner.h"
+#include "exceptions.h"
 #include <fstream>
 
 namespace YAML
@@ -32,7 +33,11 @@ namespace YAML
 
 		std::ifstream fin(fileName.c_str());
 		Scanner scanner(fin);
-		scanner.Scan();
+
+		try {
+			scanner.Scan();
+		} catch(const UnknownToken& e) {
+		}
 //		if(!scanner)
 //			return;
 
diff --git a/exceptions.h b/exceptions.h
new file mode 100644
index 0000000000..947b924e8d
--- /dev/null
+++ b/exceptions.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include <exception>
+
+namespace YAML
+{
+	class Exception: public std::exception {};
+
+	class UnknownToken: public Exception {};
+	class IllegalBlockEntry: public Exception {};
+	class IllegalMapKey: public Exception {};
+	class IllegalMapValue: public Exception {};
+	class IllegalScalar: public Exception {};
+}
diff --git a/scanner.cpp b/scanner.cpp
index f28ba67eaa..5320b29178 100644
--- a/scanner.cpp
+++ b/scanner.cpp
@@ -1,5 +1,6 @@
 #include "scanner.h"
 #include "token.h"
+#include "exceptions.h"
 
 namespace YAML
 {
@@ -10,6 +11,14 @@ namespace YAML
 
 	Scanner::~Scanner()
 	{
+		while(!m_tokens.empty()) {
+			delete m_tokens.front();
+			m_tokens.pop();
+		}
+
+		// delete limbo tokens (they're here for RAII)
+		for(std::set <Token *>::const_iterator it=m_limboTokens.begin();it!=m_limboTokens.end();++it)
+			delete *it;
 	}
 
 	///////////////////////////////////////////////////////////////////////
@@ -157,9 +166,118 @@ namespace YAML
 		return true;
 	}
 
+	// IsBlockEntry
+	bool Scanner::IsBlockEntry()
+	{
+		if(INPUT.peek() != Keys::BlockEntry)
+			return false;
+
+		INPUT.get();
+
+		// then needs a blank character (or eof)
+		if(!IsBlank()) {
+			INPUT.putback(Keys::BlockEntry);
+			return false;
+		}
+
+		INPUT.putback(Keys::BlockEntry);
+		return true;
+	}
+
+	// IsKey
+	bool Scanner::IsKey()
+	{
+		if(INPUT.peek() != Keys::Key)
+			return false;
+
+		INPUT.get();
+
+		// then needs a blank character (or eof), if we're in block context
+		if(m_flowLevel == 0 && !IsBlank()) {
+			INPUT.putback(Keys::BlockEntry);
+			return false;
+		}
+
+		INPUT.putback(Keys::BlockEntry);
+		return true;
+	}
+
+	// IsValue
+	bool Scanner::IsValue()
+	{
+		if(INPUT.peek() != Keys::Value)
+			return false;
+
+		INPUT.get();
+
+		// then needs a blank character (or eof), if we're in block context
+		if(m_flowLevel == 0 && !IsBlank()) {
+			INPUT.putback(Keys::BlockEntry);
+			return false;
+		}
+
+		INPUT.putback(Keys::BlockEntry);
+		return true;
+	}
+
+	// IsPlainScalar
+	// . Rules:
+	//   . Cannot start with a blank.
+	//   . Can never start with any of , [ ] { } # & * ! | > \' \" % @ `
+	//   . In the block context - ? : must be not be followed with a space.
+	//   . In the flow context ? : are illegal and - must not be followed with a space.
+	bool Scanner::IsPlainScalar()
+	{
+		if(IsBlank())
+			return false;
+
+		// never characters
+		std::string never = ",[]{}#&*!|>\'\"%@`";
+		for(unsigned i=0;i<never.size();i++)
+			if(INPUT.peek() == never[i])
+				return false;
+
+		// specific block/flow characters
+		if(m_flowLevel == 0) {
+			if(INPUT.peek() == '-' || INPUT.peek() == '?' || INPUT.peek() == ':') {
+				char ch = INPUT.get();
+				if(IsBlank()) {
+					INPUT.putback(ch);
+					return false;
+				}
+			}
+		} else {
+			if(INPUT.peek() == '?' || INPUT.peek() == ':')
+				return false;
+			if(INPUT.peek() == '-') {
+				INPUT.get();
+				if(IsBlank()) {
+					INPUT.putback('-');
+					return false;
+				}
+			}
+		}
+
+		return true;
+	}
+
 	///////////////////////////////////////////////////////////////////////
 	// Specialization for scanning specific tokens
 
+	// ScanAndEnqueue
+	// . Scans the token, then pushes it in the queue.
+	// . Note: we also use a set of "limbo tokens", i.e., tokens
+	//   that haven't yet been pushed. This way, if ScanToken()
+	//   throws an exception, we'll be keeping track of 'pToken'
+	//   somewhere, and it will be automatically cleaned up when
+	//   the Scanner destructs.
+	template <typename T> void Scanner::ScanAndEnqueue(T *pToken)
+	{
+		m_limboTokens.insert(pToken);
+		m_tokens.push(ScanToken(pToken));
+		m_limboTokens.erase(pToken);
+	}
+
 	// StreamStartToken
 	template <> StreamStartToken *Scanner::ScanToken(StreamStartToken *pToken)
 	{
@@ -177,7 +295,7 @@ namespace YAML
 		if(m_column > 0)
 			m_column = 0;
 
-		// TODO: unroll indentation
+		PopIndentTo(-1);
 		// TODO: "reset simple keys"
 
 		m_simpleKeyAllowed = false;
@@ -188,8 +306,8 @@ namespace YAML
 	// DocumentStartToken
 	template <> DocumentStartToken *Scanner::ScanToken(DocumentStartToken *pToken)
 	{
-		// TODO: unroll indentation
-		// TODO: reset simple keys
+		PopIndentTo(m_column);
+		// TODO: "reset simple keys"
 
 		m_simpleKeyAllowed = false;
 
@@ -202,8 +320,8 @@ namespace YAML
 	// DocumentEndToken
 	template <> DocumentEndToken *Scanner::ScanToken(DocumentEndToken *pToken)
 	{
-		// TODO: unroll indentation
-		// TODO: reset simple keys
+		PopIndentTo(m_column);
+		// TODO: "reset simple keys"
 
 		m_simpleKeyAllowed = false;
 
@@ -213,28 +331,255 @@ namespace YAML
 		return pToken;
 	}
 
+	// FlowSeqStartToken
+	template <> FlowSeqStartToken *Scanner::ScanToken(FlowSeqStartToken *pToken)
+	{
+		// TODO: "save simple key"
+		// TODO: increase flow level
+
+		m_simpleKeyAllowed = true;
+
+		// eat it
+		INPUT.get();
+
+		return pToken;
+	}
+
+	// FlowMapStartToken
+	template <> FlowMapStartToken *Scanner::ScanToken(FlowMapStartToken *pToken)
+	{
+		// TODO: "save simple key"
+		// TODO: increase flow level
+
+		m_simpleKeyAllowed = true;
+
+		// eat it
+		INPUT.get();
+
+		return pToken;
+	}
+
+	// FlowSeqEndToken
+	template <> FlowSeqEndToken *Scanner::ScanToken(FlowSeqEndToken *pToken)
+	{
+		// TODO: "remove simple key"
+		// TODO: decrease flow level
+
+		m_simpleKeyAllowed = false;
+
+		// eat it
+		INPUT.get();
+
+		return pToken;
+	}
+
+	// FlowMapEndToken
+	template <> FlowMapEndToken *Scanner::ScanToken(FlowMapEndToken *pToken)
+	{
+		// TODO: "remove simple key"
+		// TODO: decrease flow level
+
+		m_simpleKeyAllowed = false;
+
+		// eat it
+		INPUT.get();
+
+		return pToken;
+	}
+
+	// FlowEntryToken
+	template <> FlowEntryToken *Scanner::ScanToken(FlowEntryToken *pToken)
+	{
+		// TODO: "remove simple key"
+
+		m_simpleKeyAllowed = true;
+
+		// eat it
+		INPUT.get();
+
+		return pToken;
+	}
+
+	// BlockEntryToken
+	template <> BlockEntryToken *Scanner::ScanToken(BlockEntryToken *pToken)
+	{
+		// we better be in the block context!
+		if(m_flowLevel == 0) {
+			// can we put it here?
+			if(!m_simpleKeyAllowed)
+				throw IllegalBlockEntry();
+
+			PushIndentTo(m_column, true);	// , -1
+		} else {
+			// TODO: throw?
+		}
+
+		// TODO: "remove simple key"
+
+		m_simpleKeyAllowed = true;
+
+		// eat
+		INPUT.get();
+		return pToken;
+	}
+
+	// KeyToken
+	template <> KeyToken *Scanner::ScanToken(KeyToken *pToken)
+	{
+		// are we in block context?
+		if(m_flowLevel == 0) {
+			if(!m_simpleKeyAllowed)
+				throw IllegalMapKey();
+
+			PushIndentTo(m_column, false);
+		}
+
+		// TODO: "remove simple key"
+
+		// can only put a simple key here if we're in block context
+		if(m_flowLevel == 0)
+			m_simpleKeyAllowed = true;
+		else
+			m_simpleKeyAllowed = false;
+
+		// eat
+		INPUT.get();
+		return pToken;
+	}
+
+	// ValueToken
+	template <> ValueToken *Scanner::ScanToken(ValueToken *pToken)
+	{
+		// TODO: Is it a simple key?
+		if(false) {
+		} else {
+			// If not, ...
+			// are we in block context?
+			if(m_flowLevel == 0) {
+				if(!m_simpleKeyAllowed)
+					throw IllegalMapValue();
+
+				PushIndentTo(m_column, false);
+			}
+		}
+
+		// can only put a simple key here if we're in block context
+		if(m_flowLevel == 0)
+			m_simpleKeyAllowed = true;
+		else
+			m_simpleKeyAllowed = false;
+
+		// eat
+		INPUT.get();
+		return pToken;
+	}
+
+	// PlainScalarToken
+	template <> PlainScalarToken *Scanner::ScanToken(PlainScalarToken *pToken)
+	{
+		// TODO: "save simple key"
+
+		m_simpleKeyAllowed = false;
+
+		// now eat and store the scalar
+		while(1) {
+			// doc start/end tokens
+			if(IsDocumentStart() || IsDocumentEnd())
+				break;
+
+			// comment
+			if(INPUT.peek() == Keys::Comment)
+				break;
+
+			// first eat non-blanks
+			while(!IsBlank()) {
+				// illegal colon in flow context
+				if(m_flowLevel > 0 && INPUT.peek() == ':') {
+					INPUT.get();
+					if(!IsBlank()) {
+						INPUT.putback(':');
+						throw IllegalScalar();
+					}
+					INPUT.putback(':');
+				}
+
+				// characters that might end the scalar
+				// TODO: scanner.c line 3434
+			}
+		}
+
+		return pToken;
+	}
+
 	///////////////////////////////////////////////////////////////////////
 	// The main scanning function
 
-	Token *Scanner::ScanNextToken()
+	void Scanner::ScanNextToken()
 	{
 		if(!m_startedStream)
-			return ScanToken(new StreamStartToken);
+			return ScanAndEnqueue(new StreamStartToken);
 
 		ScanToNextToken();
 		// TODO: remove "obsolete potential simple keys"
-		// TODO: unroll indent
+		PopIndentTo(m_column);
 
 		if(INPUT.peek() == EOF)
-			return ScanToken(new StreamEndToken);
+			return ScanAndEnqueue(new StreamEndToken);
 
+		// are we at a document token?
 		if(IsDocumentStart())
-			return ScanToken(new DocumentStartToken);
+			return ScanAndEnqueue(new DocumentStartToken);
 
 		if(IsDocumentEnd())
-			return ScanToken(new DocumentEndToken);
+			return ScanAndEnqueue(new DocumentEndToken);
 
-		return 0;
+		// are we at a flow start/end/entry?
+		if(INPUT.peek() == Keys::FlowSeqStart)
+			return ScanAndEnqueue(new FlowSeqStartToken);
+
+		if(INPUT.peek() == Keys::FlowSeqEnd)
+			return ScanAndEnqueue(new FlowSeqEndToken);
+		
+		if(INPUT.peek() == Keys::FlowMapStart)
+			return ScanAndEnqueue(new FlowMapStartToken);
+		
+		if(INPUT.peek() == Keys::FlowMapEnd)
+			return ScanAndEnqueue(new FlowMapEndToken);
+
+		if(INPUT.peek() == Keys::FlowEntry)
+			return ScanAndEnqueue(new FlowEntryToken);
+
+		// block/map stuff?
+		if(IsBlockEntry())
+			return ScanAndEnqueue(new BlockEntryToken);
+
+		if(IsKey())
+			return ScanAndEnqueue(new KeyToken);
+
+		if(IsValue())
+			return ScanAndEnqueue(new ValueToken);
+
+		// TODO: alias/anchor/tag
+
+		// TODO: special scalars
+		if(INPUT.peek() == Keys::LiteralScalar && m_flowLevel == 0)
+			return;
+
+		if(INPUT.peek() == Keys::FoldedScalar && m_flowLevel == 0)
+			return;
+
+		if(INPUT.peek() == '\'')
+			return;
+
+		if(INPUT.peek() == '\"')
+			return;
+
+		// plain scalars
+		if(IsPlainScalar())
+			return ScanAndEnqueue(new PlainScalarToken);
+
+		// don't know what it is!
+		throw UnknownToken();
 	}
 
 	// ScanToNextToken
@@ -266,10 +611,47 @@ namespace YAML
         }
 	}
 
+	// PushIndentTo
+	// . Pushes an indentation onto the stack, and enqueues the
+	//   proper token (sequence start or mapping start).
+	void Scanner::PushIndentTo(int column, bool sequence)
+	{
+		// are we in flow?
+		if(m_flowLevel > 0)
+			return;
+
+		// is this actually an indentation?
+		if(column <= m_indents.top())
+			return;
+
+		// now push
+		m_indents.push(column);
+		if(sequence)
+			m_tokens.push(new BlockSeqStartToken);
+		else
+			m_tokens.push(new BlockMapStartToken);
+	}
+
+	// PopIndentTo
+	// . Pops indentations off the stack until we reach 'column' indentation,
+	//   and enqueues the proper token each time.
+	void Scanner::PopIndentTo(int column)
+	{
+		// are we in flow?
+		if(m_flowLevel > 0)
+			return;
+
+		// now pop away
+		while(!m_indents.empty() && m_indents.top() > column) {
+			m_indents.pop();
+			m_tokens.push(new BlockEndToken);
+		}
+	}
+
 	// temporary function for testing
 	void Scanner::Scan()
 	{
-		while(Token *pToken = ScanNextToken())
-			delete pToken;
+		while(INPUT)
+			ScanNextToken();
 	}
 }
diff --git a/scanner.h b/scanner.h
index 7fd8f5afef..9d9e282e10 100644
--- a/scanner.h
+++ b/scanner.h
@@ -4,6 +4,7 @@
 #include <string>
 #include <queue>
 #include <stack>
+#include <set>
 
 namespace YAML
 {
@@ -12,6 +13,19 @@ namespace YAML
 	namespace Keys
 	{
 		const char Comment = '#';
+		const char FlowSeqStart = '[';
+		const char FlowSeqEnd = ']';
+		const char FlowMapStart = '{';
+		const char FlowMapEnd = '}';
+		const char FlowEntry = ',';
+		const char BlockEntry = '-';
+		const char Key = '?';
+		const char Value = ':';
+		const char Alias = '*';
+		const char Anchor = '&';
+		const char Tag = '!';
+		const char LiteralScalar = '|';
+		const char FoldedScalar = '>';
 	}
 
 	class Scanner
@@ -20,8 +34,10 @@ namespace YAML
 		Scanner(std::istream& in);
 		~Scanner();
 
-		Token *ScanNextToken();
+		void ScanNextToken();
 		void ScanToNextToken();
+		void PushIndentTo(int column, bool sequence);
+		void PopIndentTo(int column);
 
 		void Scan();
 
@@ -36,6 +52,12 @@ namespace YAML
 		bool IsBlank();
 		bool IsDocumentStart();
 		bool IsDocumentEnd();
+		bool IsBlockEntry();
+		bool IsKey();
+		bool IsValue();
+		bool IsPlainScalar();
+
+		template <typename T> void ScanAndEnqueue(T *pToken);
 		template <typename T> T *ScanToken(T *pToken);
 
 	private:
@@ -45,6 +67,7 @@ namespace YAML
 
 		// the output (tokens)
 		std::queue <Token *> m_tokens;
+		std::set <Token *> m_limboTokens;
 
 		// state info
 		bool m_startedStream;
diff --git a/token.h b/token.h
index 699b93bad6..aab0af2e65 100644
--- a/token.h
+++ b/token.h
@@ -3,8 +3,25 @@
 namespace YAML
 {
 	class Token {};
+
 	class StreamStartToken: public Token {};
 	class StreamEndToken: public Token {};
 	class DocumentStartToken: public Token {};
 	class DocumentEndToken: public Token {};
+
+	class BlockSeqStartToken: public Token {};
+	class BlockMapStartToken: public Token {};
+	class BlockEndToken: public Token {};
+	class BlockEntryToken: public Token {};
+
+	class FlowSeqStartToken: public Token {};
+	class FlowMapStartToken: public Token {};
+	class FlowSeqEndToken: public Token {};
+	class FlowMapEndToken: public Token {};
+	class FlowEntryToken: public Token {};
+
+	class KeyToken: public Token {};
+	class ValueToken: public Token {};
+
+	class PlainScalarToken: public Token {};
 }
diff --git a/yaml-reader.vcproj b/yaml-reader.vcproj
index 88eb74d39c..04a440f9ab 100644
--- a/yaml-reader.vcproj
+++ b/yaml-reader.vcproj
@@ -211,6 +211,10 @@
 				RelativePath=".\document.h"
 				>
 			</File>
+			<File
+				RelativePath=".\exceptions.h"
+				>
+			</File>
 			<File
 				RelativePath=".\map.h"
 				>