diff --git a/app-proto/main.css b/app-proto/main.css
index a687aac..bdbacfb 100644
--- a/app-proto/main.css
+++ b/app-proto/main.css
@@ -104,6 +104,10 @@ details[open]:has(li) .elt-switch::after {
   font-style: italic;
 }
 
+.cst > input {
+  margin: 0px 8px 0px 0px;
+}
+
 /* display */
 
 canvas {
diff --git a/app-proto/src/add_remove.rs b/app-proto/src/add_remove.rs
index 40b0e98..ab5db70 100644
--- a/app-proto/src/add_remove.rs
+++ b/app-proto/src/add_remove.rs
@@ -66,7 +66,8 @@ fn load_gen_assemb(assembly: &Assembly) {
                 assembly.elements_by_id.with_untracked(|elts_by_id| elts_by_id["gemini_a"]),
                 assembly.elements_by_id.with_untracked(|elts_by_id| elts_by_id["gemini_b"])
             ),
-            rep: 0.5
+            rep: 0.5,
+            active: create_signal(true)
         }
     );
 }
@@ -211,7 +212,8 @@ pub fn AddRemove() -> View {
                     );
                     state.assembly.insert_constraint(Constraint {
                         args: args,
-                        rep: 0.0
+                        rep: 0.0,
+                        active: create_signal(true)
                     });
                     state.selection.update(|sel| sel.clear());
                     
diff --git a/app-proto/src/assembly.rs b/app-proto/src/assembly.rs
index c0c9959..e8dab79 100644
--- a/app-proto/src/assembly.rs
+++ b/app-proto/src/assembly.rs
@@ -16,7 +16,8 @@ pub struct Element {
 #[derive(Clone)]
 pub struct Constraint {
     pub args: (usize, usize),
-    pub rep: f64
+    pub rep: f64,
+    pub active: Signal<bool>
 }
 
 // a complete, view-independent description of an assembly
diff --git a/app-proto/src/outline.rs b/app-proto/src/outline.rs
index c980887..4e4de9c 100644
--- a/app-proto/src/outline.rs
+++ b/app-proto/src/outline.rs
@@ -136,6 +136,7 @@ pub fn Outline() -> View {
                                             let other_arg_label = assembly.elements.with(|elts| elts[other_arg].label.clone());
                                             view! {
                                                 li(class="cst") {
+                                                    input(r#type="checkbox", bind:checked=cst.active)
                                                     div(class="cst-label") { (other_arg_label) }
                                                     div(class="cst-rep") { (cst.rep) }
                                                 }