diff --git a/rogueviz/ads/display.cpp b/rogueviz/ads/display.cpp
index 822b98f1..a2f37709 100644
--- a/rogueviz/ads/display.cpp
+++ b/rogueviz/ads/display.cpp
@@ -163,21 +163,24 @@ void draw_game_cell(const cell_to_draw& cd) {
     }
   
   if(paused && c == vctr_ship && !game_over) {
-    vector<hyperpoint> pts;
-    vector<ld> times;
-    int ok = 0, bad = 0;
-    for(int i=0; i<=360; i++) {
-      hybrid::in_actual([&]{
-        auto h = ads_inverse(current_ship * vctrV_ship) * spin(i*degree) * lorentz(0, 2, 6);
-        auto cr = cross0(current * V * h);
-        pts.push_back(cr.h);
-        times.push_back(cr.shift);
-        if(cr.shift > 0 && cr.shift < 90*degree) ok++; else bad++;
-        });
-      }
-    if(bad == 0) {
+    cross_result cr;
+    hybrid::in_actual([&]{
+      auto h = ads_inverse(current_ship * vctrV_ship);
+      cr = cross0(current * V * h);
+      // println(hlog, current * V * h);
+      println(hlog, "cr shift = ", cr.shift);
+      });
+    if(cr.shift > 0 && cr.shift < M_PI) {
+      vector<hyperpoint> pts;
+      for(int i=0; i<=360; i++) {
+        hybrid::in_actual([&]{
+          auto h = ads_inverse(current_ship * vctrV_ship) * spin(i*degree);
+          auto cr = cross0_light(current * V * h);
+          pts.push_back(cr.h);
+          });
+        }
       for(auto h: pts) curvepoint(h);
-      queuecurve(shiftless(Id), 0x000000C0, 0x00000060, PPR::SUPERLINE);
+      queuecurve(shiftless(Id), 0xFF0000C0, 0x00000060, PPR::SUPERLINE);
       }
     }
   }
diff --git a/rogueviz/ads/ds-game.cpp b/rogueviz/ads/ds-game.cpp
index e76748e7..ae840d9c 100644
--- a/rogueviz/ads/ds-game.cpp
+++ b/rogueviz/ads/ds-game.cpp
@@ -190,6 +190,15 @@ cross_result ds_cross0(transmatrix T) {
   return res;
   }
 
+cross_result ds_cross0_light(transmatrix T) {
+  // h = T * (t 0 1 t); h[3] == 0
+  ld t = T[3][2] / -(T[3][0] + T[3][3]);
+  cross_result res;
+  res.shift = t;
+  res.h = T * hyperpoint(t, 0, 1, t);
+  return res;
+  }
+
 transmatrix tpt(ld x, ld y) {
   return cspin(0, 2, x * scale) * cspin(1, 2, y * scale);
   }
@@ -292,6 +301,22 @@ void view_ds_game() {
       string str = format(tformat, view_pt / time_unit);
       queuestr(shiftless(Id), .1, str, 0xFFFF00, 8);
       }
+
+    if(paused && !game_over) {
+      vector<hyperpoint> pts;
+      int ok = 0, bad = 0;
+      for(int i=0; i<=360; i++) {
+        dynamicval<eGeometry> g(geometry, gSpace435);
+        auto h = inverse(dscurrent_ship) * spin(i*degree);
+        auto cr = ds_cross0_light(dscurrent * h);
+        pts.push_back(cr.h);
+        if(cr.shift > 0) ok++; else bad++;
+        }
+      if(bad == 0) {
+        for(auto h: pts) curvepoint(h);
+        queuecurve(shiftless(Id), 0xFF0000C0, 0x00000060, PPR::SUPERLINE);
+        }
+      }
     }
   }
 
diff --git a/rogueviz/ads/math.cpp b/rogueviz/ads/math.cpp
index 8e9ecb5f..81908e1f 100644
--- a/rogueviz/ads/math.cpp
+++ b/rogueviz/ads/math.cpp
@@ -145,6 +145,19 @@ cross_result cross0(ads_matrix hz) {
   return cross_result{uhzt, t};
   }
 
+/** Similar as cross0_light but for light-like wordlines.
+ *  The point returned by cross0_light(T) is the same as the limit of cross0(T * lorentz(0, 2, v)).
+ **/
+
+cross_result cross0_light(ads_matrix hz) {
+  transmatrix uhz = unshift(hz);
+  ld t = uhz[2][3] / -(uhz[2][2] + uhz[2][0]);
+  hyperpoint uhzt = uhz * hyperpoint(t, 0, t, 1);
+  tie(uhzt[2], uhzt[3]) = make_pair(uhzt[3], -uhzt[2]);
+  if(uhzt[2] < 0) uhzt = -uhzt;
+  return cross_result{uhzt, t};
+  }
+
 /** sample from Poisson distribution */
 int rpoisson(ld lambda) {
   ld prob = randd();