diff --git a/src/cli.cr b/src/cli.cr
index 2d9557d..d8219ba 100644
--- a/src/cli.cr
+++ b/src/cli.cr
@@ -2,6 +2,7 @@ require "option_parser"
 require "digest/sha256"
 require "colorize"
 
+require "./log"
 require "./config"
 require "./build/cli"
 require "./build/run"
@@ -14,6 +15,8 @@ require "./write/run"
 
 module DocMachine
   class Cli
+    Log = DocMachine::Log.for("cli")
+
     def initialize
     end
 
@@ -28,12 +31,18 @@ module DocMachine
           "Main options:"
         ].join("\n")
 
-        opts.on("-v", "--verbose", "Enable verbosity") do |verbose|
-          config.verbose = true
+        opts.on("-v", "--verbosity LEVEL", "Change verbosity level to LEVEL (0..3)") do |verbose|
+          verbose_i = verbose.to_i
+          verbose_i = 0 if verbose.to_i < 0
+          verbose_i = 3 if verbose.to_i > 3
+          config.verbosity = ::Log::Severity.from_value(3 - verbose_i)
+        rescue ex: ArgumentError
+          Log.error { "Wrong value for parameter --verbosity" }
+          exit 1
         end
 
         opts.on("-h", "--help", "Show this help") do
-          Log.info { opts }
+          Log.notice { opts }
           exit
         end
 
@@ -47,15 +56,17 @@ module DocMachine
       end
 
       parser.parse(args)
+      ::Log.setup(config.verbosity, ::Log::IOBackend.new(formatter: BaseFormat))
+      Log.notice { "verbosity level = #{config.verbosity}" }
       Log.debug { "commands = #{commands}" }
 
       if commands.size < 1
         Log.error { parser.to_s }
-        Log.error { "ERROR: no command defined" }
+        Log.error { "No command defined" }
       end
 
       commands.each do |command|
-        # Log.info { "== Running #{command}" }
+        Log.debug { "== Running #{command}" }
         command.call()
       end
     end
diff --git a/src/config.cr b/src/config.cr
index a2f90f4..01485f1 100644
--- a/src/config.cr
+++ b/src/config.cr
@@ -5,7 +5,7 @@ require "./module"
 module DocMachine
   class Config
 
-    property verbose : Bool = false
+    property verbosity = ::Log::Severity::Notice
 
     def initialize
     end
diff --git a/src/log.cr b/src/log.cr
new file mode 100644
index 0000000..0b8bc1b
--- /dev/null
+++ b/src/log.cr
@@ -0,0 +1,38 @@
+
+require "log"
+require "colorize"
+
+struct DebugFormat < Log::StaticFormatter
+   def run
+     string @entry.severity.label[0].downcase
+     string ": "
+     source
+     string ": "
+     message
+   end
+ end
+
+struct BaseFormat < Log::StaticFormatter
+   def run
+     io = ::IO::Memory.new
+
+     color = case @entry.severity
+             when ::Log::Severity::Error
+               Colorize.colorize.red.bold
+             when ::Log::Severity::Warn
+               Colorize.colorize.red.yellow
+             when ::Log::Severity::Notice
+               Colorize.colorize.bold
+             else
+               Colorize.colorize
+             end
+
+     color.surround(io) do 
+       io << @entry.message
+     end
+
+     string io.to_s
+   end
+ end
+
+# Log.define_formatter BaseFormat, "#{severity.to_s.lstrip}(#{source}): #{message}"
diff --git a/src/main.cr b/src/main.cr
index 715054a..6f8ba11 100644
--- a/src/main.cr
+++ b/src/main.cr
@@ -1,10 +1,9 @@
 
 require "./cli"
-
-Log.define_formatter BaseFormat, "#{message}"
-
+require "./log"
 
 ::Log.setup(:notice, Log::IOBackend.new(formatter: BaseFormat))
+::Log.progname = "(root)"
 app = DocMachine::Cli.new
 app.start(ARGV)
 
diff --git a/src/write/cli.cr b/src/write/cli.cr
index d6bc1d7..c7b378f 100644
--- a/src/write/cli.cr
+++ b/src/write/cli.cr
@@ -1,9 +1,9 @@
+
 require "./config"
 require "./run"
+require "./module"
 
 module DocMachine::Write
-  Log = DocMachine::Log.for("write")
-
   class Cli
     Log = DocMachine::Write::Log.for("cli")
 
@@ -18,15 +18,20 @@ module DocMachine::Write
         end
 
         commands << ->() : Nil do
+          Log.debug { "before any" }
           if args.size < 1
-            Log.error { "ERROR: No target given!" }
+            Log.error { "No target given!" }
             exit 1 
           end
           config.target_directory = args[0]
 
+          Log.debug { "before new" }
           app = DocMachine::Write::Run.new(config)
+          Log.debug { "before prepare" }
           app.prepare
+          Log.debug { "before start" }
           app.start
+          Log.debug { "before wait" }
           app.wait
         end
       end
diff --git a/src/write/module.cr b/src/write/module.cr
new file mode 100644
index 0000000..ea6ae71
--- /dev/null
+++ b/src/write/module.cr
@@ -0,0 +1,6 @@
+
+require "../module"
+
+module DocMachine::Write
+    Log = DocMachine::Log.for("write")
+end
diff --git a/src/write/nodes/module.cr b/src/write/nodes/module.cr
new file mode 100644
index 0000000..40f614a
--- /dev/null
+++ b/src/write/nodes/module.cr
@@ -0,0 +1,6 @@
+
+require "../module"
+
+module DocMachine::Write::Nodes
+    Log = DocMachine::Write::Log.for("nodes")
+end
diff --git a/src/write/run.cr b/src/write/run.cr
index 571e337..0c2afd5 100644
--- a/src/write/run.cr
+++ b/src/write/run.cr
@@ -18,7 +18,7 @@ module DocMachine::Write
     # Verify parameters
     def prepare()
       if ! File.directory? @config.target_directory
-        Log.error { "ERROR: target must be a directory" }
+        Log.error { "Target must be a directory" }
         exit 1
       end