diff --git a/engine/canvas_modes.cpp b/engine/canvas_modes.cpp
index 9c18550..c20ba1f 100644
--- a/engine/canvas_modes.cpp
+++ b/engine/canvas_modes.cpp
@@ -20,6 +20,8 @@ void CanvasModeBasicCamera::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
         case kEventType::MouseUpL:
             break;
         case kEventType::MouseDownR:
+            if (App::I.keys[(int)kKey::KeyAlt])
+                break;
             m_draggingR = true;
             m_dragR_start = me->m_pos;
             m_pan_start = canvas->m_pan;
@@ -104,8 +106,26 @@ void CanvasModePen::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
             m_dragging = false;
             m_picking = false;
             break;
+        case kEventType::MouseDownR:
+            if (App::I.keys[(int)kKey::KeyAlt])
+            {
+                m_resizing = true;
+                m_dragging = true;
+                m_size_pos_start = m_cur_pos;
+                m_size_value_start = canvas->m_current_brush.m_tip_size;
+                node->mouse_capture();
+            }
+            break;
+        case kEventType::MouseUpR:
+            if (m_dragging && m_resizing)
+            {
+                node->mouse_release();
+                m_dragging = false;
+                m_resizing = false;
+            }
+            break;
         case kEventType::MouseMove:
-            if (m_dragging && !m_picking)
+            if (m_dragging && !m_picking && !m_resizing)
                 canvas->stroke_update(loc, me->m_pressure);
             if (m_dragging && m_picking)
             {
@@ -113,6 +133,11 @@ void CanvasModePen::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
                 canvas->m_current_brush.m_tip_color = pix;
                 App::I.color->set_color(pix);
             }
+            if (m_dragging && m_resizing)
+            {
+                auto diff = m_cur_pos - m_size_pos_start;
+                canvas->m_current_brush.m_tip_size = m_size_value_start + diff.x * 0.001f;
+            }
             m_cur_pos = loc;
             break;
         case kEventType::MouseCancel:
@@ -123,9 +148,9 @@ void CanvasModePen::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
                 node->mouse_release();
             }
             if (m_picking)
-            {
                 m_picking = false;
-            }
+            if (m_resizing)
+                m_resizing = false;
             break;
         default:
             break;
@@ -135,8 +160,9 @@ void CanvasModePen::on_MouseEvent(MouseEvent* me, glm::vec2& loc)
 void CanvasModePen::on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const glm::mat4& camera)
 {
 #ifndef __IOS__
-    if (!m_dragging && !m_picking)
+    if (!m_dragging && !m_picking || m_resizing)
     {
+        auto pos = m_resizing ? m_size_pos_start : m_cur_pos;
         ui::ShaderManager::use(ui::kShader::StrokePreview);
         ui::ShaderManager::u_int(ui::kShaderUniform::Tex, 0);
         ui::ShaderManager::u_float(ui::kShaderUniform::Alpha, canvas->m_current_brush.m_tip_flow);
@@ -147,7 +173,7 @@ void CanvasModePen::on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const
         ui::ShaderManager::u_mat4(ui::kShaderUniform::MVP,
             glm::scale(glm::vec3(1, -1, 1)) *
             ortho *
-            glm::translate(glm::vec3(m_cur_pos, 0)) *
+            glm::translate(glm::vec3(pos, 0)) *
             glm::scale(glm::vec3(canvas->m_current_brush.m_tip_size * 800.f * tip_scale))
             );
         glEnable(GL_BLEND);
diff --git a/engine/canvas_modes.h b/engine/canvas_modes.h
index d923c7b..c70c398 100644
--- a/engine/canvas_modes.h
+++ b/engine/canvas_modes.h
@@ -40,11 +40,15 @@ class CanvasModePen : public CanvasMode
     bool m_dragging = false;
     glm::vec2 m_pan_start;
     glm::vec2 m_cur_pos;
+    glm::vec2 m_size_pos_start;
+    float m_size_value_start;
     float m_camera_fov;
     float m_zoom_canvas = 1.f;
     float m_zoom_start;
     bool m_valid_brush = false;
     ui::Brush m_brush;
+    // resizing the tip
+    bool m_resizing = false;
 public:
     virtual void on_MouseEvent(MouseEvent* me, glm::vec2& loc) override;
     virtual void on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const glm::mat4& camera) override;