diff --git a/blendish.h b/blendish.h
index cc66bf6..159a2ec 100644
--- a/blendish.h
+++ b/blendish.h
@@ -192,6 +192,13 @@ typedef enum BNDcornerFlags {
 // height of horizontal scrollbar
 #define BND_SCROLLBAR_HEIGHT 14
 
+// default vertical spacing
+#define BND_VSPACING 1
+// default vertical spacing between groups
+#define BND_VSPACING_GROUP 8
+// default horizontal spacing
+#define BND_HSPACING 8
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // set the current theme all widgets will be drawn with.
diff --git a/example.cpp b/example.cpp
index c1026c5..1acc4df 100644
--- a/example.cpp
+++ b/example.cpp
@@ -24,7 +24,28 @@
 #ifndef _UI_H_
 #define _UI_H_
 
+#define UI_COLD   0x0000
+#define UI_HOT    0x0001
+#define UI_ACTIVE 0x0002
+    
+// containers
+#define UI_ROOT   0x0100
+#define UI_COLUMN 0x0101
+#define UI_ROW    0x0102
+
+// controls
+#define UI_BUTTON 0x0203
+
+#define UI_MAX_ITEMS 4096
+#define UI_MAX_BUFFERSIZE 1048576
+#define UI_MAX_DEPTH 64
+
 typedef struct UIcontext UIcontext;
+typedef unsigned long long UIhandle;
+
+typedef struct UIrect {
+    int x, y, w, h;
+} UIrect;
 
 UIcontext *uiCreateContext();
 void uiMakeCurrent(UIcontext *ctx);
@@ -36,24 +57,83 @@ int uiGetButton(int button);
 void uiSetCursor(int x, int y);
 void uiGetCursor(int *x, int *y);
 
+void uiClear();
+
+int uiItem(int parent, UIhandle handle, int kind, 
+    int w, int h, void *data, int size);
+int uiColumn(int parent, int spacing);
+int uiRow(int parent, int spacing);
+
+void uiLayout();
+
+int uiFirstChild(int item);
+int uiLastChild(int item);
+int uiNextSibling(int item);
+int uiParent(int item);
+
+void uiSetSpacing(int item, int spacing);
+int uiGetSpacing(int item);
+
+int uiGetKind(int item);
+UIrect uiGetRect(int item);
+UIrect uiGetScreenRect(int item);
+void uiSetRect(int item, int x, int y, int w, int h);
+void *uiGetData(int item);
+int uiGetChildId(int item);
+int uiGetChildCount(int item);
+int uiGetHandle(int item);
+int uiGetState(int item);
+
 #endif // _UI_H_
 
 #ifdef UI_IMPLEMENTATION
 
+#define UI_MAX_KIND 16
+
+typedef struct UIitem {
+    UIhandle handle;
+    int parent;
+    // number of kids
+    int numkids;
+    // index of kid relative to parent
+    int kidid;
+    UIrect rect;
+    int absx,absy;
+    int kind;
+    int data;
+    int spacing;
+    // index of first kid
+    int firstkid;
+    // index of last kid
+    int lastkid;
+    // index of next sibling with same parent
+    int nextitem;
+} UIitem;
+
 struct UIcontext {
-    int cx, cy;
     unsigned long long buttons;
+    int cx, cy;
+    
+    UIhandle hot;
+    UIhandle active;
+    
+    int count;    
+    UIitem items[UI_MAX_ITEMS];
+    int datasize;
+    unsigned char data[UI_MAX_BUFFERSIZE];
 };
 
 static UIcontext *ui_context = NULL;
 
 UIcontext *uiCreateContext() {
     UIcontext *ctx = (UIcontext *)malloc(sizeof(UIcontext));
+    memset(ctx, 0, sizeof(UIcontext));
     return ctx;
 }
 
 void uiMakeCurrent(UIcontext *ctx) {
     ui_context = ctx;
+    uiClear();
 }
 
 void uiDestroyContext(UIcontext *ctx) {
@@ -85,17 +165,358 @@ void uiGetCursor(int *x, int *y) {
     *y = ui_context->cy;
 }
 
+UIitem *uiItemPtr(int item) {
+    assert(ui_context && (item >= 0) && (item < ui_context->count));
+    return ui_context->items + item;
+}
+
+void uiClear() {
+    assert(ui_context);
+    ui_context->count = 1;
+    ui_context->datasize = 0;
+    ui_context->hot = 0;
+
+    // init root object    
+    UIitem *item = ui_context->items;
+    memset(item, 0, sizeof(UIitem));
+    item->parent = -1;
+    item->firstkid = -1;
+    item->lastkid = -1;
+    item->nextitem = -1;
+    item->kind = UI_ROOT;
+    item->data = -1;
+}
+
+int uiAllocItem(int parent, UIhandle handle, int kind, void *data, int size) {
+    assert(ui_context && (ui_context->count < UI_MAX_ITEMS));
+    assert((size >= 0) && ((ui_context->datasize+size) <= UI_MAX_BUFFERSIZE));
+    assert(parent >= 0);
+    int idx = ui_context->count++;
+    UIitem *item = uiItemPtr(idx);
+    memset(item, 0, sizeof(UIitem));
+    item->parent = parent;
+    item->handle = handle;
+    item->firstkid = -1;
+    item->lastkid = -1;
+    item->nextitem = -1;
+    item->kidid = ui_context->items[parent].numkids++;
+    if (ui_context->items[parent].lastkid < 0) {
+        ui_context->items[parent].firstkid = idx;
+        ui_context->items[parent].lastkid = idx;
+    } else {
+        ui_context->items[ui_context->items[parent].lastkid].nextitem = idx;
+        ui_context->items[parent].lastkid = idx;
+    }
+    item->kind = kind;
+    item->data = -1;
+    if (data && size) {
+        item->data = ui_context->datasize;
+        ui_context->datasize += size;
+        memcpy(ui_context->data + item->data, data, size);
+    }
+    return idx;
+}
+
+int uiItem( 
+        int parent, UIhandle handle, int kind, int w, int h, void *data, int size) {
+    int idx = uiAllocItem(parent, handle, kind, data, size);
+    UIitem *item = uiItemPtr(idx);
+    item->rect.w = w;
+    item->rect.h = h;
+    return idx;
+}
+
+void uiSetSpacing(int item, int spacing) {
+    uiItemPtr(item)->spacing = spacing;
+}
+
+int uiGetSpacing(int item) {
+    return uiItemPtr(item)->spacing;
+}
+
+int uiColumn(int parent, int spacing) {
+    int idx = uiItem(parent, 0, UI_COLUMN, 0, 0, NULL, 0);
+    uiSetSpacing(idx, spacing);
+    return idx;
+}
+
+int uiRow(int parent, int spacing) {
+    int idx = uiItem(parent, 0, UI_ROW, 0, 0, NULL, 0);
+    uiSetSpacing(idx, spacing);
+    return idx;
+}
+
+UIrect uiGetRect(int item) {
+    return uiItemPtr(item)->rect;
+}
+
+UIrect uiGetScreenRect(int item) {
+    UIitem *pitem = uiItemPtr(item);
+    UIrect rect = pitem->rect;
+    rect.x = pitem->absx;
+    rect.y = pitem->absy;
+    return rect;
+}
+
+void uiSetRect(int item, int x, int y, int w, int h) {
+    UIitem *pitem = uiItemPtr(item);
+    pitem->rect.w = w;
+    pitem->rect.h = h;
+    pitem->rect.x = x;
+    pitem->rect.y = y;
+}
+
+int uiFirstChild(int item) {
+    return uiItemPtr(item)->firstkid;
+}
+
+int uiLastChild(int item) {
+    return uiItemPtr(item)->lastkid;
+}
+
+int uiNextSibling(int item) {
+    return uiItemPtr(item)->nextitem;
+}
+
+int uiParent(int item) {
+    return uiItemPtr(item)->parent;
+}
+
+int uiGetKind(int item) {
+    return uiItemPtr(item)->kind;
+}
+
+void *uiGetData(int item) {
+    UIitem *pitem = uiItemPtr(item);
+    if (pitem->data < 0) return NULL;
+    return ui_context->data + pitem->data;
+}
+
+int uiGetHandle(int item) {
+    return uiItemPtr(item)->handle;
+}
+
+int uiGetChildId(int item) {
+    return uiItemPtr(item)->kidid;
+}
+
+int uiGetChildCount(int item) {
+    return uiItemPtr(item)->numkids;
+}
+
+void uiLayoutItem(int item, int x, int y);
+void uiLayoutChildren(int item, int x, int y) {
+    int kid = uiFirstChild(item);
+    while (kid > 0) {
+        uiLayoutItem(kid, x, y);
+        kid = uiNextSibling(kid);
+    }
+}
+
+void uiLayoutItem(int item, int x, int y) {
+    UIrect rect = uiGetRect(item);
+    rect.x += x;
+    rect.y += y;
+    
+    switch(uiGetKind(item)) {
+        case UI_COLUMN:
+        case UI_ROOT: {
+            int kid = uiFirstChild(item);
+            while (kid > 0) {
+                UIitem *pitem = uiItemPtr(kid);
+                if (!pitem->rect.w || (pitem->rect.w > rect.w)) {
+                    pitem->rect.w = rect.w;
+                }
+                kid = uiNextSibling(kid);
+            }
+            
+            uiLayoutChildren(item, rect.x, rect.y);
+            
+            int spacing = uiItemPtr(item)->spacing;
+            int h = -spacing;
+            // stack kids vertically
+            kid = uiFirstChild(item);
+            while (kid > 0) {
+                UIitem *pitem = uiItemPtr(kid);
+                h += spacing;
+                pitem->rect.y = h;
+                h += pitem->rect.h;
+                kid = uiNextSibling(kid);
+            }
+            
+            if (h > rect.h) {
+                uiItemPtr(item)->rect.h = h;
+            }
+            
+        } break;
+        case UI_ROW: {
+            uiLayoutChildren(item, rect.x, rect.y);
+
+            int spacing = uiItemPtr(item)->spacing;
+            
+            // figure out height of row
+            // also see how much horizontal space is used
+            int lastkidid = uiGetChildCount(item)-1;
+            lastkidid = (lastkidid<0)?0:lastkidid;
+            int w = spacing*lastkidid;
+            // how many children have no explicit width?
+            int numdynkids = 0;
+            int kid = uiFirstChild(item);
+            while (kid > 0) {
+                UIitem *pitem = uiItemPtr(kid);
+                if (pitem->rect.h > rect.h)
+                    rect.h = pitem->rect.h;
+                if (!pitem->rect.w)
+                    numdynkids++;
+                else
+                    w += pitem->rect.w;
+                kid = uiNextSibling(kid);
+            }
+            uiItemPtr(item)->rect.h = rect.h;
+            
+            int space = rect.w - w;
+            // distribute remaining width across children
+            int dw = numdynkids?(space / numdynkids):0;
+            dw = (dw<0)?0:dw;
+            // rounding error
+            space -= numdynkids*dw;
+            
+            w = -spacing;
+            // stack kids horizontally
+            kid = uiFirstChild(item);
+            while (kid > 0) {
+                UIitem *pitem = uiItemPtr(kid);
+                w += spacing;
+                pitem->rect.x = w;
+                if (!pitem->rect.w) {
+                    --numdynkids;
+                    // round last kid
+                    if (!numdynkids)
+                        dw += space;
+                    pitem->rect.w = dw;
+                }
+                w += pitem->rect.w;
+                kid = uiNextSibling(kid);
+            }
+        } break;
+        default: break;
+    }
+}
+
+void uiUpdateItemState(int item, int x, int y) {
+    UIitem *pitem = uiItemPtr(item);
+    pitem->absx = pitem->rect.x+x;
+    pitem->absy = pitem->rect.y+y;
+    
+    if (pitem->handle) {
+        int cx = ui_context->cx - pitem->absx;
+        int cy = ui_context->cy - pitem->absy;
+        if ((cx>=0)
+            && (cy>=0)
+            && (cx<pitem->rect.w)
+            && (cy<pitem->rect.h)) {
+            ui_context->hot = pitem->handle;
+            
+            if (!ui_context->active && uiGetButton(0)) {
+                ui_context->active = pitem->handle;
+            }
+        }
+    }
+    
+    int kid = uiFirstChild(item);
+    while (kid > 0) {
+        uiUpdateItemState(kid, pitem->absx, pitem->absy);
+        kid = uiNextSibling(kid);
+    }
+
+}
+
+void uiLayout() {
+    uiLayoutItem(0, 0, 0);
+    uiUpdateItemState(0, 0, 0);
+    if (!uiGetButton(0)) {
+        ui_context->active = 0;
+    }
+}
+
+int uiIsActive(int item) {
+    assert(ui_context);
+    return (ui_context->active == uiItemPtr(item)->handle)?1:0;
+}
+
+int uiIsHot(int item) {
+    assert(ui_context);
+    return (ui_context->hot == uiItemPtr(item)->handle)?1:0;
+}
+
+int uiGetState(int item) {
+    return (!uiIsHot(item))?UI_COLD:(uiIsActive(item))?UI_ACTIVE:UI_HOT;
+
+}
+
 #endif // UI_IMPLEMENTATION
 
 ////////////////////////////////////////////////////////////////////////////////
 
+typedef struct UIData {
+    int iconid;
+    const char *label;
+} UIData;
+
+////////////////////////////////////////////////////////////////////////////////
+
 void init(NVGcontext *vg) {
     bndSetFont(nvgCreateFont(vg, "system", "../droidsans.ttf"));
     bndSetIconImage(nvgCreateImage(vg, "../blender_icons16.png"));
 }
 
-void draw(NVGcontext *vg, float w, float h) {
+int cornerFlags(int item) {
+    int parent = uiParent(item);
+    int spacing = uiGetSpacing(parent);
+    if (spacing >= 0) return BND_CORNER_NONE;
+    int numkids = uiGetChildCount(parent);
+    int numid = uiGetChildId(item);
+    if (numkids == 0) return BND_CORNER_NONE;
+    switch(uiGetKind(parent)) {
+        case UI_COLUMN: {
+            if (!numid) return BND_CORNER_DOWN;
+            else if (numid == numkids-1) return BND_CORNER_TOP;
+            else return BND_CORNER_ALL;
+        } break;
+        case UI_ROW: {
+            if (!numid) return BND_CORNER_RIGHT;
+            else if (numid == numkids-1) return BND_CORNER_LEFT;
+            else return BND_CORNER_ALL;
+        } break;
+        default: break;
+    }
+    return BND_CORNER_NONE;
+}
 
+void drawUI(NVGcontext *vg, int item, int x, int y) {
+    UIData *data = (UIData *)uiGetData(item);
+    UIrect rect = uiGetRect(item);
+    rect.x += x;
+    rect.y += y;
+    
+    switch(uiGetKind(item)) {
+        case UI_BUTTON: {
+            assert(data);
+            bndToolButton(vg,rect.x,rect.y,rect.w,rect.h,
+                cornerFlags(item),(BNDwidgetState)uiGetState(item),
+                data->iconid,data->label);
+        } break;
+        default: break;
+    }
+    
+    int kid = uiFirstChild(item);
+    while (kid > 0) {
+        drawUI(vg, kid, rect.x, rect.y);
+        kid = uiNextSibling(kid);
+    }
+}
+
+void draw(NVGcontext *vg, float w, float h) {
     bndBackground(vg, 0, 0, w, h);
     
     int x = 10;
@@ -280,9 +701,46 @@ void draw(NVGcontext *vg, float w, float h) {
     x += BND_TOOL_WIDTH-1;
     bndRadioButton(vg,x,y,BND_TOOL_WIDTH,BND_WIDGET_HEIGHT,BND_CORNER_LEFT,
         BND_DEFAULT,BND_ICONID(5,11),NULL);
-         
     
-   
+    uiClear();
+    
+    uiSetRect(0,600,10,250,400);
+    
+    int col = uiColumn(0,1);
+    UIData data = { BND_ICONID(6,3), "Item 1" };
+    uiItem(col, 1, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+    data.label = "Item 2";
+    uiItem(col, 2, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+    { // nested row    
+        int row = uiRow(col,-1);
+        data.label = "Item 3.0";
+        uiItem(row, 3, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+        data.label = NULL;
+        data.iconid = BND_ICONID(0,10);
+        uiItem(row, 4, UI_BUTTON, BND_TOOL_WIDTH, BND_WIDGET_HEIGHT, &data, sizeof(data));
+        data.label = NULL;
+        data.iconid = BND_ICONID(1,10);
+        uiItem(row, 5, UI_BUTTON, BND_TOOL_WIDTH, BND_WIDGET_HEIGHT, &data, sizeof(data));
+        data.iconid = BND_ICONID(6,3);
+        data.label = "Item 3.3";
+        uiItem(row, 6, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+    }
+    
+    { // nested column
+        int col2 = uiColumn(col,-2);
+        data.label = "Item 4.0";
+        uiItem(col2, 7, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+        data.label = "Item 4.1";
+        uiItem(col2, 8, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));        
+    }
+    
+    data.label = "Item 5";
+    uiItem(col, 9, UI_BUTTON, 0, BND_WIDGET_HEIGHT, &data, sizeof(data));
+    
+    uiLayout();
+    
+    
+    drawUI(vg, 0, 0, 0);
 }
 
 ////////////////////////////////////////////////////////////////////////////////