diff --git a/mark.h b/mark.h
index b64da47..cc26c6c 100644
--- a/mark.h
+++ b/mark.h
@@ -7,6 +7,8 @@ typedef enum {
   Mark_flag_input = 1 << 1,
   Mark_flag_lock = 1 << 2,
   Mark_flag_output = 1 << 3,
+  Mark_flag_sleep_phase0 = 1 << 4,
+  Mark_flag_sleep_phase1 = 1 << 4,
 } Mark_flags;
 
 typedef struct {
diff --git a/sim.c b/sim.c
index 7e3f3d2..db34ff4 100644
--- a/sim.c
+++ b/sim.c
@@ -1,6 +1,9 @@
 #include "field.h"
+#include "mark.h"
 #include "sim.h"
 
+#define OPER_INLINE static inline
+
 static Glyph const indexed_glyphs[] = {
     '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
     'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
@@ -45,40 +48,80 @@ static inline Glyph glyphs_mod(Glyph a, Glyph b) {
   return indexed_glyphs[ib == 0 ? 0 : (ia % ib)];
 }
 
-static inline void act_a(Field* f, Usz y, Usz x) {
-  Glyph inp0 = field_peek_relative(f, y, x, 0, 1);
-  Glyph inp1 = field_peek_relative(f, y, x, 0, 2);
+static inline void oper_move_relative_or_explode(Glyph* field_buffer,
+                                                 Usz field_height,
+                                                 Usz field_width, Glyph moved,
+                                                 Usz y, Usz x, Isz delta_y,
+                                                 Isz delta_x) {
+  Isz y0 = (Isz)y + delta_y;
+  Isz x0 = (Isz)x + delta_x;
+  if (y0 >= (Isz)field_height || x0 >= (Isz)field_width || y0 < 0 || x0 < 0) {
+    field_buffer[y * field_width + x] = '*';
+    return;
+  }
+  Glyph* at_dest = field_buffer + (Usz)y0 * field_width + (Usz)x0;
+  if (*at_dest != '.') {
+    field_buffer[y * field_width + x] = '*';
+    return;
+  }
+  *at_dest = moved;
+  field_buffer[y * field_width + x] = '.';
+}
+
+static inline void oper_a_phase1(Field* field, Usz y, Usz x) {
+  Glyph inp0 = field_peek_relative(field, y, x, 0, 1);
+  Glyph inp1 = field_peek_relative(field, y, x, 0, 2);
   if (inp0 != '.' && inp1 != '.') {
-    Glyph t = glyphs_sum(inp0, inp1);
-    field_poke_relative(f, y, x, 1, 0, t);
+    Glyph g = glyphs_sum(inp0, inp1);
+    field_poke_relative(field, y, x, 1, 0, g);
   }
 }
 
-static inline void act_m(Field* f, Usz y, Usz x) {
-  Glyph inp0 = field_peek_relative(f, y, x, 0, 1);
-  Glyph inp1 = field_peek_relative(f, y, x, 0, 2);
+static inline void oper_E_phase0(Field* field, Usz y, Usz x) {
+  oper_move_relative_or_explode(field->buffer, field->height, field->width, 'E',
+                                y, x, 0, 1);
+}
+
+static inline void oper_m_phase1(Field* field, Usz y, Usz x) {
+  Glyph inp0 = field_peek_relative(field, y, x, 0, 1);
+  Glyph inp1 = field_peek_relative(field, y, x, 0, 2);
   if (inp0 != '.' && inp1 != '.') {
-    Glyph t = glyphs_mod(inp0, inp1);
-    field_poke_relative(f, y, x, 1, 0, t);
+    Glyph g = glyphs_mod(inp0, inp1);
+    field_poke_relative(field, y, x, 1, 0, g);
   }
 }
 
-void orca_run(Field* f) {
-  Usz ny = f->height;
-  Usz nx = f->width;
-  Glyph* f_buffer = f->buffer;
+void orca_run(Field* field) {
+  Usz ny = field->height;
+  Usz nx = field->width;
+  Glyph* field_buffer = field->buffer;
+  // Phase 0
+  for (Usz iy = 0; iy < ny; ++iy) {
+    Glyph* row = field_buffer + iy * nx;
+    for (Usz ix = 0; ix < nx; ++ix) {
+      Glyph c = row[ix];
+      switch (c) {
+      case 'E':
+        oper_E_phase0(field, iy, ix);
+        break;
+      }
+    }
+  }
+  // Phase 1
   for (Usz iy = 0; iy < ny; ++iy) {
-    Glyph* row = f_buffer + iy * nx;
+    Glyph* row = field_buffer + iy * nx;
     for (Usz ix = 0; ix < nx; ++ix) {
       Glyph c = row[ix];
       switch (c) {
       case 'a':
-        act_a(f, iy, ix);
+        oper_a_phase1(field, iy, ix);
         break;
       case 'm':
-        act_m(f, iy, ix);
+        oper_m_phase1(field, iy, ix);
         break;
       }
     }
   }
 }
+
+#undef OPER_INLINE