document many unknown fields

src/Episode3/Card.cc

@@ -717,7 +717,7 @@ int32_t Card::move_to_location(const Location& loc) {
           G_EnqueueAnimation_Ep3_6xB4x2C cmd;
           cmd.change_type = 1;
           cmd.client_id = other_ps->client_id;
-          cmd.unknown_a2[0] = trap_card_id;
+          cmd.trap_card_id = trap_card_id;
           s->send(cmd);
         }
       }
@@ -736,7 +736,8 @@ int32_t Card::move_to_location(const Location& loc) {
         cmd.change_type = 0;
         cmd.card_refs.clear(0xFFFF);
         cmd.card_refs[0] = this->card_ref;
-        cmd.unknown_a2.clear(0xFFFFFFFF);
+        cmd.trap_card_id = 0xFFFFFFFF;
+        cmd.unknown_a3 = 0xFFFFFFFF;
         s->send(cmd);
         return 0;
       }

src/Episode3/PlayerState.cc

@@ -617,7 +617,8 @@ void PlayerState::discard_and_redraw_hand() {
     cmd.change_type = 3;
     cmd.client_id = this->client_id;
     cmd.card_refs.clear(0xFFFF);
-    cmd.unknown_a2.clear(0xFFFFFFFF);
+    cmd.trap_card_id = 0xFFFFFFFF;
+    cmd.unknown_a3 = 0xFFFFFFFF;
     s->send(cmd);
   }
 
@@ -721,7 +722,8 @@ bool PlayerState::do_mulligan() {
     cmd.change_type = 3;
     cmd.client_id = this->client_id;
     cmd.card_refs.clear(0xFFFF);
-    cmd.unknown_a2.clear(0xFFFFFFFF);
+    cmd.trap_card_id = 0xFFFFFFFF;
+    cmd.unknown_a3 = 0xFFFFFFFF;
     s->send(cmd);
   }
 

src/Episode3/Server.cc

@@ -1164,8 +1164,8 @@ void Server::move_phase_after() {
               cmd.loc.x = trap_x;
               cmd.loc.y = trap_y;
               cmd.loc.direction = static_cast<Direction>(trap_type);
-              cmd.unknown_a2[0] = trap_card_id;
-              cmd.unknown_a2[1] = 0xFFFFFFFF;
+              cmd.trap_card_id = trap_card_id;
+              cmd.unknown_a3 = 0xFFFFFFFF;
               this->send(cmd);
             }
           }