diff --git a/rogueviz/ru/classes.cpp b/rogueviz/ru/classes.cpp
index 59894e8f..2c354cf8 100644
--- a/rogueviz/ru/classes.cpp
+++ b/rogueviz/ru/classes.cpp
@@ -228,6 +228,8 @@ struct entity {
 
   data get_dat();
 
+  virtual bool hidden() { return false; }
+
   struct bbox get_pixel_bbox_at(xy, ld scalex = 1, ld scaley = 1);
   struct bbox get_pixel_bbox() { return get_pixel_bbox_at(where); }
 
@@ -295,6 +297,7 @@ struct entity {
 struct statdata {
   statarray<ld> stats;
   int jump_control, coyote_time, hallucinating;
+  ld detect_area;
   void reset();
   vector<tuple<power*, mod, int>> mods;
   };
@@ -326,6 +329,7 @@ struct man : public entity {
 
   virtual int max_hp() { return 10 * current.stats[stat::con]; }
 
+  bool can_see(entity& e);
   man() {
     facing = 1; attack_facing = 1;
     for(auto s: allstats) base_stats[s] = 10;
@@ -465,6 +469,7 @@ struct vtrap : public entity {
   xy siz() override { return {6, 18}; }
   string glyph() override { return "^"; }
   color_t color() override { return 0xD00000FF; }
+  bool hidden() override { return true; }
   void act() override;
   string get_name() override { return "moving trap"; }
   string get_help() override { return "A deadly but invisible trap."; }
diff --git a/rogueviz/ru/man.cpp b/rogueviz/ru/man.cpp
index 298f85da..f178346f 100644
--- a/rogueviz/ru/man.cpp
+++ b/rogueviz/ru/man.cpp
@@ -41,6 +41,7 @@ void statdata::reset() {
   for(auto i: allstats) stats[i] = m.base_stats[i];
   coyote_time = 0;
   jump_control = 0;
+  detect_area = 0;
   hallucinating = false;
   mods.clear();
   }
@@ -85,6 +86,11 @@ void man::act() {
   check_fountains();
   }
 
+bool man::can_see(entity& e) {
+  ld d = hdist(to_hyper(m.where), to_hyper(e.where));
+  return d < inverse_wvolarea_auto(m.current.detect_area);
+  }
+
 void man::on_kill() {
   entity::on_kill();
   if(extra_life->flags & ACTIVE)
diff --git a/rogueviz/ru/randeff.cpp b/rogueviz/ru/randeff.cpp
index 75a813a7..15e09bf2 100644
--- a/rogueviz/ru/randeff.cpp
+++ b/rogueviz/ru/randeff.cpp
@@ -31,7 +31,20 @@ randeff jump_bubble("Bubble", "Lets you create bubbles to reach higher places.",
 randeff jump_light("Lightness", "Causes you to be less affected by gravity.", "You feel lighter!", [] (data &d) { });
 
 // trap powers
-randeff trap_detect("Detect traps", "Lets you see traps and secret passages in a circle around you.", "You see things you could not see before!", [] (data &d) { });
+randeff trap_detect("Detect traps", "Lets you see traps and secret passages in a circle around you.", "You see things you could not see before!", [] (data &d) {
+  bool grow = gframeid > m.last_action + 10;
+  auto& nd = m.next.detect_area;
+  nd = m.current.detect_area;
+  if(grow) {
+    nd += 0.01 / game_fps * m.current.stats[stat::wis];
+    if(nd > 5) nd = 5;
+    }
+  else {
+    nd *= (1 - 5. / game_fps);
+    if(nd < 0) nd = 0;
+    }
+  });
+
 randeff trap_snake("Snake Hair", "Lets you create snakes that can be used to disarm traps and secret passages.", "You grow snakes on your head!", [] (data &d) { });
 randeff trap_disarm("Disarm traps", "Lets you see all traps on the level for a short time, and to attack them with your [weapon] to destroy them.", "You suddenly feel able to disarm traps with your [weapon]!", [] (data &d) { });
 
diff --git a/rogueviz/ru/render.cpp b/rogueviz/ru/render.cpp
index cf23208f..69c9685a 100644
--- a/rogueviz/ru/render.cpp
+++ b/rogueviz/ru/render.cpp
@@ -263,14 +263,25 @@ void man::draw() {
       }
     }
   effects.resize(efs - effects.begin());
+
+  if(m.current.detect_area > 0) {
+    ld r = inverse_wvolarea_auto(m.current.detect_area);
+    for(int a=0; a<=360; a++) {
+      auto h = from_hyper(eupush(to_hyper(m.where)) * xspinpush0(a*1._deg, r));
+      curvepoint(eupush(h.x, h.y) * C0);
+      }
+    queuecurve(scrm, 0x800080, 0, PPR::LINE);
+    }
   }
 
 void render_room_objects(room *r) {
   initquickqueue();
   if(r == current_room && m.visible_inv() && m.existing) m.draw();
   for(auto& e: r->entities)
-    if(e->existing && (cmode == mode::editmap || (e->visible(r) && e->visible_inv())))
+    if(e->existing && (cmode == mode::editmap || (e->visible(r) && e->visible_inv()))) {
+      if(e->hidden() && !m.can_see(*e)) continue;
       e->draw();
+      }
   quickqueue();
   }