diff --git a/.gitignore b/.gitignore
index eacf10a3..4a610ba1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,35 +1,5 @@
-MAIN.cs
-MAIN.exe
-Kernel.dll
-Kernel.dll.so
-PerlTask.dll
-SAFE.dll
-SAFE.dll.so
-SAFE.cs
-SAFE_ast.store
-CORE.dll
-CORE.dll.so
-CORE.cs
-CORE_ast.store
-Test.dll
-Test.dll.so
-Test.cs
-Test_ast.store
-Threads.dll
-Threads.dll.so
-Threads.cs
-Threads_ast.store
-MONKEY_TYPING.dll
-MONKEY_TYPING.dll.so
-MONKEY_TYPING.cs
-MONKEY_TYPING_ast.store
-RegexEngine.dll
-RegexEngine.so
-RegexEngine.cs
-RegexEngine_ast.store
 *.swp
 *.pmc
-syml
 .STD_build_stamp
 .STD_checkout_stamp
 STD_checkout
diff --git a/CompilerDriver.pm b/CompilerDriver.pm
index 7c7dd040..d7f09968 100644
--- a/CompilerDriver.pm
+++ b/CompilerDriver.pm
@@ -8,7 +8,7 @@ use Sub::Exporter -setup => {
 };
 
 use Time::HiRes 'time';
-
+use File::Basename;
 use autodie ':all';
 
 open ::NIECZA_OUT, ">&", \*STDOUT;
@@ -30,8 +30,21 @@ use Storable;
 use Niecza::Grammar ();
 use Niecza::Actions ();
 
-# TODO
-my $builddir = File::Spec->curdir;
+my $builddir;
+{
+    my $libdir = dirname($INC{'CompilerDriver.pm'});
+    $builddir = File::Spec->catdir($libdir, "build");
+}
+File::Path::make_path($builddir);
+
+sub build_file { File::Spec->catfile($builddir, $_[1]) }
+
+sub metadata_for {
+    my ($cl, $unit) = @_;
+    $unit =~ s/::/./g;
+
+    Storable::retrieve(File::Spec->catfile($builddir, "$unit.store"))
+}
 
 {
     package
@@ -100,7 +113,7 @@ sub compile {
     $::UNITNAME =~ s|[\\/]|.|g;
     $STD::ALL = {};
 
-    $::SETTING_RESUME = retrieve($args{lang} . '.store')->{setting}
+    $::SETTING_RESUME = CompilerDriver->metadata_for($args{lang})->{setting}
         unless $args{lang} eq 'NULL';
     $::UNITDEPS{$args{lang}} = 1 if $args{lang} ne 'NULL';
 
@@ -109,6 +122,9 @@ sub compile {
 
     my $ast;
     my $basename = $::UNITNAME || 'MAIN';
+    my $csfile = File::Spec->catfile($builddir, "$basename.cs");
+    my $outname = File::Spec->catfile($builddir,
+        $basename . ($args{main} ? ".exe" : ".dll"));
 
     my @phases = (
         [ 'parse', sub {
@@ -124,7 +140,7 @@ sub compile {
         [ 'to_anf', sub { $ast->to_anf } ],
         [ 'writecs', sub {
 
-            open ::NIECZA_OUT, ">", "$basename.cs";
+            open ::NIECZA_OUT, ">", $csfile;
             binmode ::NIECZA_OUT, ":utf8";
             print ::NIECZA_OUT <<EOH;
 using System;
@@ -137,18 +153,24 @@ EOH
             if ($::SETTING_RESUME || $::niecza_mod_symbols) {
                 my $blk = { setting => $::SETTING_RESUME,
                             syml    => $::niecza_mod_symbols };
-                store $blk, "$basename.store";
+                store $blk, File::Spec->catfile($builddir, "$basename.store");
             }
-            $ast = undef; } ],
+            $ast = undef;
+        } ],
         [ 'gmcs', sub {
             delete $::UNITDEPS{$basename};
-            system "gmcs", ($args{main} ? () : ("/target:library")),
+            my @args = ("gmcs",
+                ($args{main} ? () : ("/target:library")),
+                "/lib:$builddir",
                 "/r:Kernel.dll", (map { "/r:$_.dll" } sort keys %::UNITDEPS),
-                "/out:${basename}." . ($args{main} ? 'exe' : 'dll'),
-                "${basename}.cs"; } ],
+                "/out:$outname",
+                $csfile);
+            print STDERR "@args\n" if $args{stagetime};
+            system @args;
+        } ],
         [ 'aot', sub {
-            system "mono", "--aot", "${basename}." .
-                ($args{main} ? 'exe' : 'dll'); } ]);
+            system "mono", "--aot", $outname;
+        } ]);
 
     for my $p (@phases) {
         next if $p->[0] eq 'aot' && !$args{aot};
diff --git a/Decl.pm b/Decl.pm
index f1ddf7dd..42fc4a6d 100644
--- a/Decl.pm
+++ b/Decl.pm
@@ -482,7 +482,7 @@ use CgOp;
 
     sub preinit_code {
         my ($self, $body) = @_;
-        my $scope = Storable::retrieve($self->unit . ".store")->{setting};
+        my $scope = CompilerDriver->metadata_for($self->unit)->{setting};
 
         CodeGen->know_module($self->unit);
         CgOp::prog(
diff --git a/Niecza.proj b/Niecza.proj
index e07a1679..3e5a635f 100644
--- a/Niecza.proj
+++ b/Niecza.proj
@@ -1,6 +1,6 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003"
     ToolsVersion="2.0">
-    <UsingTask TaskName="Perl" AssemblyFile="PerlTask.dll"/>
+    <UsingTask TaskName="Perl" AssemblyFile="build\PerlTask.dll"/>
     <PropertyGroup>
         <!-- Tool paths -->
         <Subversion>svn</Subversion>
@@ -28,9 +28,10 @@
 
     <Target Name="Test" DependsOnTargets="CORE.dll;Test.dll;WriteVersion;PerlTask">
         <Perl Code="use CompilerDriver ':all'; compile(stopafter => 'writecs', lang => 'CORE', main => 1, file => 'test.pl');"/>
-        <Csc Sources="MAIN.cs" TargetType="exe" OutputAssembly="MAIN.exe"
+        <Csc Sources="build\MAIN.cs" TargetType="exe" AdditionalLibPaths="build"
+            OutputAssembly="build\MAIN.exe"
             References="Test.dll;SAFE.dll;CORE.dll;Kernel.dll"/>
-        <Exec Command="prove -e mono MAIN.exe"/>
+        <Exec Command="prove -e mono build\MAIN.exe"/>
     </Target>
 
     <Target Name="WriteVersion">
@@ -38,40 +39,50 @@
     </Target>
 
     <!-- Libraries -->
-    <Target Name="Kernel.dll" Inputs="Kernel.cs;Cursor.cs" Outputs="Kernel.dll">
+    <Target Name="Kernel.dll" Inputs="Kernel.cs;Cursor.cs"
+        Outputs="build\Kernel.dll">
         <Csc Sources="Kernel.cs;Cursor.cs" TargetType="library"
-            OutputAssembly="Kernel.dll"/>
-        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot Kernel.dll"/>
+            OutputAssembly="build\Kernel.dll"/>
+        <Exec Condition="$(UseAOT) == 'Y'"
+            Command="mono --aot build\Kernel.dll"/>
     </Target>
 
-    <Target Name="CORE.cs" Inputs="@(CompilerPerl);SAFE.store;CORE.setting" Outputs="CORE.cs;CORE.store" DependsOnTargets="BuildSTD;SAFE.cs;Grammar;PerlTask">
+    <Target Name="CORE.cs" Inputs="@(CompilerPerl);build\SAFE.store;CORE.setting" Outputs="build\CORE.cs;build\CORE.store" DependsOnTargets="BuildSTD;SAFE.cs;Grammar;PerlTask">
         <Perl Code="use CompilerDriver ':all'; compile(stopafter => 'writecs', lang => 'SAFE', file => 'CORE.setting');"/>
     </Target>
 
-    <Target Name="SAFE.cs" Inputs="@(CompilerPerl);SAFE.setting" Outputs="SAFE.cs;SAFE.store" DependsOnTargets="BuildSTD;Grammar;PerlTask">
+    <Target Name="SAFE.cs" Inputs="@(CompilerPerl);SAFE.setting"
+        Outputs="build\SAFE.cs;build\SAFE.store"
+        DependsOnTargets="BuildSTD;Grammar;PerlTask">
         <Perl Code="use CompilerDriver ':all'; compile(stopafter => 'writecs', lang => 'NULL', file => 'SAFE.setting');"/>
     </Target>
 
-    <Target Name="Test.cs" Inputs="@(CompilerPerl);CORE.store;Test.pm6" Outputs="Test.cs;Test.store" DependsOnTargets="CORE.cs;BuildSTD;Grammar;PerlTask">
+    <Target Name="Test.cs" Inputs="@(CompilerPerl);build\CORE.store;Test.pm6"
+        Outputs="build\Test.cs;build\Test.store"
+        DependsOnTargets="CORE.cs;BuildSTD;Grammar;PerlTask">
         <Perl Code="use CompilerDriver ':all'; compile(stopafter => 'writecs', lang => 'CORE', file => 'Test.pm6');"/>
     </Target>
 
-    <Target Name="CORE.dll" Inputs="CORE.cs;SAFE.dll;Kernel.dll" Outputs="CORE.dll" DependsOnTargets="CORE.cs;SAFE.dll;Kernel.dll">
-        <Csc Sources="CORE.cs" TargetType="library"
-            OutputAssembly="CORE.dll" References="SAFE.dll;Kernel.dll"/>
-        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot CORE.dll"/>
+    <Target Name="CORE.dll" Inputs="build\CORE.cs;build\SAFE.dll;build\Kernel.dll" Outputs="build\CORE.dll" DependsOnTargets="CORE.cs;SAFE.dll;Kernel.dll">
+        <Csc Sources="build\CORE.cs" TargetType="library"
+            AdditionalLibPaths="build" OutputAssembly="build\CORE.dll"
+            References="SAFE.dll;Kernel.dll"/>
+        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot build\CORE.dll"/>
     </Target>
 
-    <Target Name="SAFE.dll" Inputs="SAFE.cs;Kernel.dll" Outputs="SAFE.dll" DependsOnTargets="SAFE.cs;Kernel.dll">
-        <Csc Sources="SAFE.cs" TargetType="library"
-            OutputAssembly="SAFE.dll" References="Kernel.dll"/>
-        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot SAFE.dll"/>
+    <Target Name="SAFE.dll" Inputs="build\SAFE.cs;build\Kernel.dll"
+        Outputs="build\SAFE.dll" DependsOnTargets="SAFE.cs;Kernel.dll">
+        <Csc Sources="build\SAFE.cs" TargetType="library"
+            AdditionalLibPaths="build" OutputAssembly="build\SAFE.dll"
+            References="Kernel.dll"/>
+        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot build\SAFE.dll"/>
     </Target>
 
-    <Target Name="Test.dll" Inputs="Test.cs;CORE.dll;Kernel.dll" Outputs="Test.dll" DependsOnTargets="Test.cs;CORE.dll;Kernel.dll">
-        <Csc Sources="Test.cs" TargetType="library"
-            OutputAssembly="Test.dll" References="CORE.dll;SAFE.dll;Kernel.dll"/>
-        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot Test.dll"/>
+    <Target Name="Test.dll" Inputs="build\Test.cs;build\CORE.dll;build\Kernel.dll" Outputs="build\Test.dll" DependsOnTargets="Test.cs;CORE.dll;Kernel.dll">
+        <Csc Sources="build\Test.cs" TargetType="library"
+            AdditionalLibPaths="build" OutputAssembly="build\Test.dll"
+            References="CORE.dll;SAFE.dll;Kernel.dll"/>
+        <Exec Condition="$(UseAOT) == 'Y'" Command="mono --aot build\Test.dll"/>
     </Target>
 
     <!-- Proper compiler bits -->
@@ -112,9 +123,9 @@
             ContinueOnError="true"/>
     </Target>
 
-    <Target Name="PerlTask" Inputs="PerlTask.cs" Outputs="PerlTask.dll">
+    <Target Name="PerlTask" Inputs="PerlTask.cs" Outputs="build\PerlTask.dll">
         <Csc Sources="PerlTask.cs" TargetType="library"
-            OutputAssembly="PerlTask.dll"
+            OutputAssembly="build\PerlTask.dll"
             References="Microsoft.Build.Framework.dll;Microsoft.Build.Utilities.dll"/>
     </Target>
 </Project>
diff --git a/build/.gitignore b/build/.gitignore
new file mode 100644
index 00000000..72e8ffc0
--- /dev/null
+++ b/build/.gitignore
@@ -0,0 +1 @@
+*
diff --git a/niecza_eval b/niecza_eval
index b372d55d..ef0f5dd4 100755
--- a/niecza_eval
+++ b/niecza_eval
@@ -53,7 +53,8 @@ $lang = 'SAFE' if $safe;
 sub run {
     compile(main => !$module, stopafter => $stopafter, aot => $aot,
         stagetime => $stagestats, lang => $lang, safe => $safe, @_);
-    system 'mono MAIN.exe' if !$module && !$stopafter;
+    system 'mono', CompilerDriver->build_file('MAIN.exe')
+        if !$module && !$stopafter;
 }
 
 if (@ARGV) {