diff --git a/app-proto/inversive-display/src/inversive.frag b/app-proto/inversive-display/src/inversive.frag
index db1a3c0..51bc0ff 100644
--- a/app-proto/inversive-display/src/inversive.frag
+++ b/app-proto/inversive-display/src/inversive.frag
@@ -40,7 +40,7 @@ uniform vec2 radius;
 uniform float opacity;
 uniform float highlight;
 uniform int layer_threshold;
-uniform bool use_test_construction;
+uniform bool test_mode;
 
 // light and camera
 const float focal_slope = 0.3;
@@ -134,40 +134,18 @@ void main() {
     vec2 scr = (2.*gl_FragCoord.xy - resolution) / shortdim;
     vec3 dir = vec3(focal_slope * scr, -1.);
     
-    // initialize two spheres
-    vecInv sphere_list_internal [SPHERE_MAX];
-    vec3 color_list_internal [SPHERE_MAX];
-    if (use_test_construction) {
-        /* DEBUG */
-        // spheres 0 and 1 are identical in the test construction hard-coded
-        // here and the construction passed in through uniforms. sphere 2 has
-        // a different radius in the construction; we can use that to show that
-        // the switch is working
-        sphere_list_internal[0] = sphere(vec3(0.5, 0.5, -5. + ctrl.x), radius.x);
-        sphere_list_internal[1] = sphere(vec3(-0.5, -0.5, -5. + ctrl.y), radius.y);
-        sphere_list_internal[2] = sphere(vec3(-0.5, 0.5, -5.), 0.5);
-        color_list_internal[0] = vec3(1., 0.25, 0.);
-        color_list_internal[1] = vec3(0., 0.25, 1.);
-        color_list_internal[2] = vec3(0.25, 0., 1.0);
-    } else {
-        for (int i = 0; i < sphere_cnt; ++i) {
-            sphere_list_internal[i] = sphere_list[i];
-            color_list_internal[i] = color_list[i];
-        }
-    }
-    
     // cast rays through the spheres
     vec2 depth_pairs [SPHERE_MAX];
     taggedFrag frags [2*SPHERE_MAX];
     int frag_cnt = 0;
     for (int i = 0; i < sphere_cnt; ++i) {
-        vec2 hit_depths = sphere_cast(sphere_list_internal[i], dir);
+        vec2 hit_depths = sphere_cast(sphere_list[i], dir);
         if (!isnan(hit_depths[0])) {
-            frags[frag_cnt] = sphere_shading(sphere_list_internal[i], hit_depths[0] * dir, color_list_internal[i], i);
+            frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[0] * dir, color_list[i], i);
             ++frag_cnt;
         }
         if (!isnan(hit_depths[1])) {
-            frags[frag_cnt] = sphere_shading(sphere_list_internal[i], hit_depths[1] * dir, color_list_internal[i], i);
+            frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i);
             ++frag_cnt;
         }
     }
@@ -202,7 +180,7 @@ void main() {
         
         // cusps
         float cusp_cos = abs(dot(dir, frag0.normal));
-        float cusp_threshold = 2.*sqrt(ixn_threshold * sphere_list_internal[frag0.id].lt.s);
+        float cusp_threshold = 2.*sqrt(ixn_threshold * sphere_list[frag0.id].lt.s);
         float cusp_highlight = highlight * (1. - smoothstep(2./3.*cusp_threshold, 1.5*cusp_threshold, cusp_cos));
         frags[i].color = mix(frags[i].color, vec4(1.), cusp_highlight);
     }
diff --git a/app-proto/inversive-display/src/main.rs b/app-proto/inversive-display/src/main.rs
index 5a9b875..a5bfedc 100644
--- a/app-proto/inversive-display/src/main.rs
+++ b/app-proto/inversive-display/src/main.rs
@@ -97,7 +97,7 @@ fn main() {
         let opacity = create_signal(0.5);
         let highlight = create_signal(0.2);
         let layer_threshold = create_signal(0.0);
-        let use_test_construction = create_signal(false);
+        let debug_mode = create_signal(false);
         
         // display
         let display = create_node_ref();
@@ -186,7 +186,7 @@ fn main() {
             let opacity_loc = ctx.get_uniform_location(&program, "opacity");
             let highlight_loc = ctx.get_uniform_location(&program, "highlight");
             let layer_threshold_loc = ctx.get_uniform_location(&program, "layer_threshold");
-            let use_test_construction_loc = ctx.get_uniform_location(&program, "use_test_construction");
+            let debug_mode_loc = ctx.get_uniform_location(&program, "debug_mode");
             
             // create a vertex array and bind it to the graphics context
             let vertex_array = ctx.create_vertex_array().unwrap();
@@ -244,7 +244,7 @@ fn main() {
                 ctx.uniform1f(opacity_loc.as_ref(), opacity.get() as f32);
                 ctx.uniform1f(highlight_loc.as_ref(), highlight.get() as f32);
                 ctx.uniform1i(layer_threshold_loc.as_ref(), layer_threshold.get() as i32);
-                ctx.uniform1i(use_test_construction_loc.as_ref(), use_test_construction.get() as i32);
+                ctx.uniform1i(debug_mode_loc.as_ref(), debug_mode.get() as i32);
                 
                 // draw the scene
                 ctx.draw_arrays(WebGl2RenderingContext::TRIANGLES, 0, VERTEX_CNT as i32);
@@ -329,11 +329,11 @@ fn main() {
                     )
                 }
                 div(class="control") {
-                    label(for="use-test-construction") { "Use test values" }
+                    label(for="debug-mode") { "Debug mode" }
                     input(
                         type="checkbox",
-                        id="use-test-construction",
-                        bind:checked=use_test_construction
+                        id="debug-mode",
+                        bind:checked=debug_mode
                     )
                 }
             }