diff --git a/basis/core-graphics/core-graphics.factor b/basis/core-graphics/core-graphics.factor
index 5e95e2e36e..924f7130f0 100644
--- a/basis/core-graphics/core-graphics.factor
+++ b/basis/core-graphics/core-graphics.factor
@@ -105,6 +105,15 @@ CONSTANT: kCGLRendererGenericFloatID HEX: 00020400
 
 FUNCTION: CGLError CGLSetParameter ( CGLContextObj ctx, CGLContextParameter pname, GLint* params ) ;
 
+FUNCTION: CGDirectDisplayID CGMainDisplayID ( ) ;
+
+FUNCTION: CGError CGDisplayHideCursor ( CGDirectDisplayID display ) ;
+FUNCTION: CGError CGDisplayShowCursor ( CGDirectDisplayID display ) ;
+
+FUNCTION: CGError CGAssociateMouseAndMouseCursorPosition ( boolean_t connected ) ;
+
+FUNCTION: CGError CGWarpMouseCursorPosition ( CGPoint newCursorPosition ) ;
+
 <PRIVATE
 
 : bitmap-flags ( -- flags )
diff --git a/basis/core-graphics/types/types.factor b/basis/core-graphics/types/types.factor
index 13e4285ea1..0acdad9c0c 100644
--- a/basis/core-graphics/types/types.factor
+++ b/basis/core-graphics/types/types.factor
@@ -90,5 +90,8 @@ TYPEDEF: void* CGContextRef
 TYPEDEF: uint CGBitmapInfo
 
 TYPEDEF: int CGLError
+TYPEDEF: int CGError
+TYPEDEF: uint CGDirectDisplayID
+TYPEDEF: int boolean_t
 TYPEDEF: void* CGLContextObj
-TYPEDEF: int CGLContextParameter
\ No newline at end of file
+TYPEDEF: int CGLContextParameter
diff --git a/basis/math/rectangles/rectangles.factor b/basis/math/rectangles/rectangles.factor
index 90174d144e..340eafa37d 100644
--- a/basis/math/rectangles/rectangles.factor
+++ b/basis/math/rectangles/rectangles.factor
@@ -21,6 +21,8 @@ M: rect pprint*
 
 : rect-extent ( rect -- loc ext ) rect-bounds over v+ ;
 
+: rect-center ( rect -- center ) rect-bounds 2 v/n v+ ;
+
 : with-rect-extents ( rect1 rect2 loc-quot: ( loc1 loc2 -- ) ext-quot: ( ext1 ext2 -- ) -- )
     [ [ rect-extent ] bi@ ] 2dip bi-curry* bi* ; inline
 
diff --git a/basis/ui/backend/backend.factor b/basis/ui/backend/backend.factor
index 9c844d3663..63d551798c 100755
--- a/basis/ui/backend/backend.factor
+++ b/basis/ui/backend/backend.factor
@@ -31,4 +31,8 @@ HOOK: offscreen-pixels ui-backend ( world -- alien w h )
     '[ select-gl-context @ ]
     [ flush-gl-context gl-error ] bi ; inline
 
-HOOK: (with-ui) ui-backend ( quot -- )
\ No newline at end of file
+HOOK: (with-ui) ui-backend ( quot -- )
+
+HOOK: (grab-input) ui-backend ( handle -- )
+
+HOOK: (ungrab-input) ui-backend ( handle -- )
diff --git a/basis/ui/backend/cocoa/cocoa.factor b/basis/ui/backend/cocoa/cocoa.factor
index ef5c80dcdb..47a3bfc1a6 100755
--- a/basis/ui/backend/cocoa/cocoa.factor
+++ b/basis/ui/backend/cocoa/cocoa.factor
@@ -122,6 +122,17 @@ M:: cocoa-ui-backend (open-window) ( world -- )
 M: cocoa-ui-backend (close-window) ( handle -- )
     window>> -> release ;
 
+M: cocoa-ui-backend (grab-input) ( handle -- )
+    0 CGAssociateMouseAndMouseCursorPosition drop
+    CGMainDisplayID CGDisplayHideCursor drop
+    window>> -> frame CGRect>rect rect-center
+    first2 <CGPoint> CGWarpMouseCursorPosition drop ;
+
+M: cocoa-ui-backend (ungrab-input) ( handle -- )
+    drop
+    CGMainDisplayID CGDisplayShowCursor drop
+    1 CGAssociateMouseAndMouseCursorPosition drop ;
+
 M: cocoa-ui-backend close-window ( gadget -- )
     find-world [
         handle>> [
diff --git a/basis/ui/backend/windows/windows.factor b/basis/ui/backend/windows/windows.factor
index 24ae72740f..c2d330b9dd 100755
--- a/basis/ui/backend/windows/windows.factor
+++ b/basis/ui/backend/windows/windows.factor
@@ -706,6 +706,14 @@ M: windows-ui-backend beep ( -- )
 : hwnd>RECT ( hwnd -- RECT )
     "RECT" <c-object> [ GetWindowRect win32-error=0/f ] keep ;
 
+M: windows-ui-backend (grab-input) ( handle -- )
+    0 ShowCursor drop
+    hWnd>> hwnd>RECT ClipCursor drop ;
+M: windows-ui-backend (ungrab-input) ( handle -- )
+    drop
+    f ClipCursor drop
+    1 ShowCursor drop ;
+
 : fullscreen-flags ( -- n )
     { WS_CAPTION WS_BORDER WS_THICKFRAME } flags ; inline
 
diff --git a/basis/ui/gadgets/worlds/worlds.factor b/basis/ui/gadgets/worlds/worlds.factor
index 3568559eac..eec5666f0e 100755
--- a/basis/ui/gadgets/worlds/worlds.factor
+++ b/basis/ui/gadgets/worlds/worlds.factor
@@ -11,7 +11,7 @@ CONSTANT: default-world-pixel-format-attributes
     { windowed double-buffered T{ depth-bits { value 16 } } }
 
 TUPLE: world < track
-    active? focused?
+    active? focused? grab-input?
     layers
     title status status-owner
     text-handle handle images
@@ -20,6 +20,7 @@ TUPLE: world < track
 
 TUPLE: world-attributes
     { world-class initial: world }
+    grab-input?
     title
     status
     gadgets
@@ -63,13 +64,15 @@ M: world request-focus-on ( child gadget -- )
     vertical swap new-track
         t >>root?
         t >>active?
-        { 0 0 } >>window-loc ;
+        { 0 0 } >>window-loc
+        f >>grab-input? ;
 
 : apply-world-attributes ( world attributes -- world )
     {
         [ title>> >>title ]
         [ status>> >>status ]
         [ pixel-format-attributes>> >>pixel-format-attributes ]
+        [ grab-input?>> >>grab-input? ]
         [ gadgets>> [ 1 track-add ] each ]
     } cleave ;
 
diff --git a/basis/ui/ui.factor b/basis/ui/ui.factor
index b73de68e26..d53d4c6753 100644
--- a/basis/ui/ui.factor
+++ b/basis/ui/ui.factor
@@ -41,14 +41,23 @@ SYMBOL: windows
     lose-focus swap each-gesture
     gain-focus swap each-gesture ;
 
+: ?grab-input ( world -- )
+    dup grab-input?>> [ handle>> (grab-input) ] [ drop ] if ;
+
+: ?ungrab-input ( world -- )
+    dup grab-input?>> [ handle>> (ungrab-input) ] [ drop ] if ;
+
 : focus-world ( world -- )
     t >>focused?
-    dup raised-window
-    focus-path f focus-gestures ;
+    [ ?grab-input ] [
+        dup raised-window
+        focus-path f focus-gestures
+    ] bi ;
 
 : unfocus-world ( world -- )
     f >>focused?
-    focus-path f swap focus-gestures ;
+    [ ?ungrab-input ]
+    [ focus-path f swap focus-gestures ] bi ;
 
 : try-to-open-window ( world -- )
     {
diff --git a/basis/windows/user32/user32.factor b/basis/windows/user32/user32.factor
index 1e694bcbe4..b6caa7c039 100644
--- a/basis/windows/user32/user32.factor
+++ b/basis/windows/user32/user32.factor
@@ -654,7 +654,7 @@ FUNCTION: HWND ChildWindowFromPoint ( HWND hWndParent, POINT point ) ;
 ! FUNCTION: ClientThreadSetup
 ! FUNCTION: ClientToScreen
 ! FUNCTION: CliImmSetHotKey
-! FUNCTION: ClipCursor
+FUNCTION: int ClipCursor ( RECT* clipRect ) ;
 FUNCTION: BOOL CloseClipboard ( ) ;
 ! FUNCTION: CloseDesktop
 ! FUNCTION: CloseWindow
@@ -1363,7 +1363,7 @@ CONSTANT: HWND_TOP f
 ! FUNCTION: SetWindowWord
 ! FUNCTION: SetWinEventHook
 ! FUNCTION: ShowCaret
-! FUNCTION: ShowCursor
+FUNCTION: int ShowCursor ( BOOL show ) ;
 ! FUNCTION: ShowOwnedPopups
 ! FUNCTION: ShowScrollBar
 ! FUNCTION: ShowStartGlass
diff --git a/extra/terrain/terrain.factor b/extra/terrain/terrain.factor
index 50c88d6f00..3f94b93138 100644
--- a/extra/terrain/terrain.factor
+++ b/extra/terrain/terrain.factor
@@ -186,5 +186,6 @@ M: terrain-world pref-dim* drop { 640 480 } ;
                 double-buffered
                 T{ depth-bits { value 24 } }
             } }
+            { grab-input? t }
         } open-window
     ] with-ui ;