Recursively handle ferried bodies

PonderingSystem now recursively ticks bodies, starting with unferried bodies at the top level, and recursively ticking their passengers. This fixes the second issue described in 8f1c4f1 -- that passengers may be ticked before their ferries, causing it to use out-of-date information about the ferry's location.

2 files changed, 637 insertions, 600 deletions

@@ -15,15 +15,6 @@
 
 void PonderingSystem::tick(double dt)
 {
-  auto& realizable = game_.getEntityManager().
-    getComponent<RealizableComponent>(
-      game_.getSystemManager().getSystem<RealizingSystem>().getSingleton());
-
-  id_type mapEntity = realizable.activeMap;
-
-  auto& mappable = game_.getEntityManager().
-    getComponent<MappableComponent>(mapEntity);
-
   auto entities = game_.getEntityManager().getEntitiesWithComponents<
     PonderableComponent,
     TransformableComponent>();
@@ -33,750 +24,791 @@ void PonderingSystem::tick(double dt)
     auto& ponderable = game_.getEntityManager().
       getComponent<PonderableComponent>(entity);
 
-    if (!ponderable.active || ponderable.frozen)
+    // We will recursively process ferried bodies after their ferries have been
+    // processed, so hold off on processing ferried bodies at the top level.
+    if (ponderable.ferried)
     {
       continue;
     }
 
-    auto& transformable = game_.getEntityManager().
-      getComponent<TransformableComponent>(entity);
+    tickBody(
+      entity,
+      dt,
+      entities);
+  }
+}
 
-    // Accelerate
-    ponderable.velX += ponderable.accelX * dt;
-    ponderable.velY += ponderable.accelY * dt;
+void PonderingSystem::initializeBody(
+  id_type entity,
+  PonderableComponent::Type type)
+{
+  auto& ponderable = game_.getEntityManager().
+    emplaceComponent<PonderableComponent>(entity, type);
 
-    if ((ponderable.type == PonderableComponent::Type::freefalling)
-      && (ponderable.velY > TERMINAL_VELOCITY))
-    {
-      ponderable.velY = TERMINAL_VELOCITY;
-    }
+  if (type == PonderableComponent::Type::freefalling)
+  {
+    ponderable.accelY = NORMAL_GRAVITY;
+  }
+}
 
-    const double oldX = transformable.x;
-    const double oldY = transformable.y;
-    const double oldRight = oldX + transformable.w;
-    const double oldBottom = oldY + transformable.h;
+void PonderingSystem::initPrototype(id_type prototype)
+{
+  auto& ponderable = game_.getEntityManager().
+    getComponent<PonderableComponent>(prototype);
 
-    CollisionResult result;
+  ponderable.velX = 0.0;
+  ponderable.velY = 0.0;
+  ponderable.accelX = 0.0;
+  ponderable.accelY = 0.0;
+  ponderable.grounded = false;
+  ponderable.frozen = false;
+  ponderable.collidable = true;
+  ponderable.ferried = false;
+  ponderable.passengers.clear();
+}
 
-    if (ponderable.ferried)
-    {
-      auto& ferryTrans = game_.getEntityManager().
-        getComponent<TransformableComponent>(ponderable.ferry);
-
-      result.newX = ferryTrans.x + ponderable.relX;
-      result.newY = ferryTrans.y + ponderable.relY;
-    } else {
-      result.newX = transformable.x;
-      result.newY = transformable.y;
-    }
+void PonderingSystem::unferry(id_type entity)
+{
+  auto& ponderable = game_.getEntityManager().
+    getComponent<PonderableComponent>(entity);
 
-    result.newX += ponderable.velX * dt;
-    result.newY += ponderable.velY * dt;
+  if (ponderable.ferried)
+  {
+    ponderable.ferried = false;
 
-    bool oldGrounded = ponderable.grounded;
-    ponderable.grounded = false;
+    auto& ferryPonder = game_.getEntityManager().
+      getComponent<PonderableComponent>(ponderable.ferry);
 
-    // Find horizontal collisions.
-    if (result.newX < oldX)
-    {
-      bool boundaryCollision = false;
-      auto it = mappable.leftBoundaries.lower_bound(oldX);
+    ferryPonder.passengers.erase(entity);
+  }
+}
 
-      // Find the axis distance of the closest environmental boundary.
-      for (;
-          (it != std::end(mappable.leftBoundaries)) &&
-            (it->first >= result.newX);
-          it++)
-      {
-        // Check that the boundary is in range for the other axis.
-        if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
-        {
-          // We have a collision!
-          boundaryCollision = true;
+void PonderingSystem::tickBody(
+  id_type entity,
+  double dt,
+  const std::set<id_type>& entities)
+{
+  auto& ponderable = game_.getEntityManager().
+    getComponent<PonderableComponent>(entity);
 
-          break;
-        }
-      }
+  if (!ponderable.active || ponderable.frozen)
+  {
+    continue;
+  }
 
-      // Find a list of potential colliders, sorted so that the closest is
-      // first.
-      std::vector<id_type> colliders;
+  auto& realizable = game_.getEntityManager().
+    getComponent<RealizableComponent>(
+      game_.getSystemManager().getSystem<RealizingSystem>().getSingleton());
 
-      for (id_type collider : entities)
-      {
-        // Can't collide with self.
-        if (collider == entity)
-        {
-          continue;
-        }
+  id_type mapEntity = realizable.activeMap;
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+  auto& mappable = game_.getEntityManager().
+    getComponent<MappableComponent>(mapEntity);
 
-        // Only check objects that are active.
-        if (!colliderPonder.active)
-        {
-          continue;
-        }
+  auto& transformable = game_.getEntityManager().
+    getComponent<TransformableComponent>(entity);
 
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
-
-        // Check if the entity would move into the potential collider,
-        if ((colliderTrans.x + colliderTrans.w > result.newX) &&
-            // that it wasn't already colliding,
-            (colliderTrans.x + colliderTrans.w <= oldX) &&
-            // that the position on the other axis is in range,
-            (colliderTrans.y + colliderTrans.h > oldY) &&
-            (colliderTrans.y < oldBottom) &&
-            // and that the collider is not farther away than the environmental
-            // boundary.
-            (!boundaryCollision ||
-              (colliderTrans.x + colliderTrans.w >= it->first)))
-        {
-          colliders.push_back(collider);
-        }
-      }
+  // Accelerate
+  ponderable.velX += ponderable.accelX * dt;
+  ponderable.velY += ponderable.accelY * dt;
 
-      std::sort(
-        std::begin(colliders),
-        std::end(colliders),
-        [&] (id_type left, id_type right) {
-          auto& leftTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(left);
+  if ((ponderable.type == PonderableComponent::Type::freefalling)
+    && (ponderable.velY > TERMINAL_VELOCITY))
+  {
+    ponderable.velY = TERMINAL_VELOCITY;
+  }
 
-          auto& rightTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(right);
+  const double oldX = transformable.x;
+  const double oldY = transformable.y;
+  const double oldRight = oldX + transformable.w;
+  const double oldBottom = oldY + transformable.h;
 
-          return (rightTrans.x < leftTrans.x);
-        });
+  CollisionResult result;
 
-      for (id_type collider : colliders)
-      {
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
+  if (ponderable.ferried)
+  {
+    auto& ferryTrans = game_.getEntityManager().
+      getComponent<TransformableComponent>(ponderable.ferry);
+
+    result.newX = ferryTrans.x + ponderable.relX;
+    result.newY = ferryTrans.y + ponderable.relY;
+  } else {
+    result.newX = transformable.x;
+    result.newY = transformable.y;
+  }
 
-        // Check if the entity would still move into the potential collider.
-        if (colliderTrans.x + colliderTrans.w <= result.newX)
-        {
-          break;
-        }
+  result.newX += ponderable.velX * dt;
+  result.newY += ponderable.velY * dt;
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+  bool oldGrounded = ponderable.grounded;
+  ponderable.grounded = false;
 
-        processCollision(
-          entity,
-          collider,
-          Direction::left,
-          colliderPonder.colliderType,
-          colliderTrans.x + colliderTrans.w,
-          colliderTrans.y,
-          colliderTrans.y + colliderTrans.h,
-          result);
+  // Find horizontal collisions.
+  if (result.newX < oldX)
+  {
+    bool boundaryCollision = false;
+    auto it = mappable.leftBoundaries.lower_bound(oldX);
+
+    // Find the axis distance of the closest environmental boundary.
+    for (;
+        (it != std::end(mappable.leftBoundaries)) &&
+          (it->first >= result.newX);
+        it++)
+    {
+      // Check that the boundary is in range for the other axis.
+      if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
+      {
+        // We have a collision!
+        boundaryCollision = true;
 
-        if (result.stopProcessing)
-        {
-          break;
-        }
+        break;
       }
+    }
 
-      // If movement hasn't been stopped by an intermediary object, and
-      // collision checking hasn't been stopped, process the environmental
-      // boundaries closest to the entity.
-      if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
-      {
-        double boundaryAxis = it->first;
+    // Find a list of potential colliders, sorted so that the closest is
+    // first.
+    std::vector<id_type> colliders;
 
-        for (;
-            (it != std::end(mappable.leftBoundaries)) &&
-              (it->first == boundaryAxis);
-            it++)
-        {
-          if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
-          {
-            processCollision(
-              entity,
-              mapEntity,
-              Direction::left,
-              it->second.type,
-              it->first,
-              it->second.lower,
-              it->second.upper,
-              result);
-
-            if (result.stopProcessing)
-            {
-              break;
-            }
-          }
-        }
-      }
-    } else if (result.newX > oldX)
+    for (id_type collider : entities)
     {
-      bool boundaryCollision = false;
-      auto it = mappable.rightBoundaries.lower_bound(oldRight);
-
-      // Find the axis distance of the closest environmental boundary.
-      for (;
-          (it != std::end(mappable.rightBoundaries))
-            && (it->first <= (result.newX + transformable.w));
-          it++)
+      // Can't collide with self.
+      if (collider == entity)
       {
-        // Check that the boundary is in range for the other axis.
-        if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
-        {
-          // We have a collision!
-          boundaryCollision = true;
-
-          break;
-        }
+        continue;
       }
 
-      // Find a list of potential colliders, sorted so that the closest is
-      // first.
-      std::vector<id_type> colliders;
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-      for (id_type collider : entities)
+      // Only check objects that are active.
+      if (!colliderPonder.active)
       {
-        // Can't collide with self.
-        if (collider == entity)
-        {
-          continue;
-        }
-
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
-
-        // Only check objects that are active.
-        if (!colliderPonder.active)
-        {
-          continue;
-        }
+        continue;
+      }
 
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
-
-        // Check if the entity would move into the potential collider,
-        if ((colliderTrans.x < result.newX + transformable.w) &&
-            // that it wasn't already colliding,
-            (colliderTrans.x >= oldRight) &&
-            // that the position on the other axis is in range,
-            (colliderTrans.y + colliderTrans.h > oldY) &&
-            (colliderTrans.y < oldBottom) &&
-            // and that the collider is not farther away than the environmental
-            // boundary.
-            (!boundaryCollision || (colliderTrans.x <= it->first)))
-        {
-          colliders.push_back(collider);
-        }
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
+
+      // Check if the entity would move into the potential collider,
+      if ((colliderTrans.x + colliderTrans.w > result.newX) &&
+          // that it wasn't already colliding,
+          (colliderTrans.x + colliderTrans.w <= oldX) &&
+          // that the position on the other axis is in range,
+          (colliderTrans.y + colliderTrans.h > oldY) &&
+          (colliderTrans.y < oldBottom) &&
+          // and that the collider is not farther away than the environmental
+          // boundary.
+          (!boundaryCollision ||
+            (colliderTrans.x + colliderTrans.w >= it->first)))
+      {
+        colliders.push_back(collider);
       }
+    }
 
-      std::sort(
-        std::begin(colliders),
-        std::end(colliders),
-        [&] (id_type left, id_type right) {
-          auto& leftTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(left);
+    std::sort(
+      std::begin(colliders),
+      std::end(colliders),
+      [&] (id_type left, id_type right) {
+        auto& leftTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(left);
 
-          auto& rightTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(right);
+        auto& rightTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(right);
 
-          return (leftTrans.x < rightTrans.x);
-        });
+        return (rightTrans.x < leftTrans.x);
+      });
 
-      for (id_type collider : colliders)
-      {
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
+    for (id_type collider : colliders)
+    {
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
 
-        // Check if the entity would still move into the potential collider.
-        if (colliderTrans.x >= result.newX + transformable.w)
-        {
-          break;
-        }
+      // Check if the entity would still move into the potential collider.
+      if (colliderTrans.x + colliderTrans.w <= result.newX)
+      {
+        break;
+      }
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-        processCollision(
-          entity,
-          collider,
-          Direction::right,
-          colliderPonder.colliderType,
-          colliderTrans.x,
-          colliderTrans.y,
-          colliderTrans.y + colliderTrans.h,
-          result);
+      processCollision(
+        entity,
+        collider,
+        Direction::left,
+        colliderPonder.colliderType,
+        colliderTrans.x + colliderTrans.w,
+        colliderTrans.y,
+        colliderTrans.y + colliderTrans.h,
+        result);
 
-        if (result.stopProcessing)
-        {
-          break;
-        }
+      if (result.stopProcessing)
+      {
+        break;
       }
+    }
 
-      // If movement hasn't been stopped by an intermediary object, and
-      // collision checking hasn't been stopped, process the environmental
-      // boundaries closest to the entity.
-      if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
-      {
-        double boundaryAxis = it->first;
+    // If movement hasn't been stopped by an intermediary object, and
+    // collision checking hasn't been stopped, process the environmental
+    // boundaries closest to the entity.
+    if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
+    {
+      double boundaryAxis = it->first;
 
-        for (;
-            (it != std::end(mappable.rightBoundaries)) &&
-              (it->first == boundaryAxis);
-            it++)
+      for (;
+          (it != std::end(mappable.leftBoundaries)) &&
+            (it->first == boundaryAxis);
+          it++)
+      {
+        if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
         {
-          if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
+          processCollision(
+            entity,
+            mapEntity,
+            Direction::left,
+            it->second.type,
+            it->first,
+            it->second.lower,
+            it->second.upper,
+            result);
+
+          if (result.stopProcessing)
           {
-            processCollision(
-              entity,
-              mapEntity,
-              Direction::right,
-              it->second.type,
-              it->first,
-              it->second.lower,
-              it->second.upper,
-              result);
-
-            if (result.stopProcessing)
-            {
-              break;
-            }
+            break;
           }
         }
       }
     }
-
-    // Find vertical collisions
-    result.touchedWall = false;
-
-    if ((!result.stopProcessing) && (result.newY < oldY))
+  } else if (result.newX > oldX)
+  {
+    bool boundaryCollision = false;
+    auto it = mappable.rightBoundaries.lower_bound(oldRight);
+
+    // Find the axis distance of the closest environmental boundary.
+    for (;
+        (it != std::end(mappable.rightBoundaries))
+          && (it->first <= (result.newX + transformable.w));
+        it++)
     {
-      bool boundaryCollision = false;
-      auto it = mappable.upBoundaries.lower_bound(oldY);
-
-      // Find the axis distance of the closest environmental boundary.
-      for (;
-          (it != std::end(mappable.upBoundaries)) &&
-            (it->first >= result.newY);
-          it++)
+      // Check that the boundary is in range for the other axis.
+      if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
       {
-        // Check that the boundary is in range for the other axis.
-        if ((result.newX + transformable.h > it->second.lower) &&
-            (result.newX < it->second.upper))
-        {
-          // We have a collision!
-          boundaryCollision = true;
+        // We have a collision!
+        boundaryCollision = true;
 
-          break;
-        }
+        break;
       }
+    }
 
-      // Find a list of potential colliders, sorted so that the closest is
-      // first.
-      std::vector<id_type> colliders;
+    // Find a list of potential colliders, sorted so that the closest is
+    // first.
+    std::vector<id_type> colliders;
 
-      for (id_type collider : entities)
+    for (id_type collider : entities)
+    {
+      // Can't collide with self.
+      if (collider == entity)
       {
-        // Can't collide with self.
-        if (collider == entity)
-        {
-          continue;
-        }
+        continue;
+      }
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-        // Only check objects that are active.
-        if (!colliderPonder.active)
-        {
-          continue;
-        }
+      // Only check objects that are active.
+      if (!colliderPonder.active)
+      {
+        continue;
+      }
 
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
-
-        // Check if the entity would move into the potential collider,
-        if ((colliderTrans.y + colliderTrans.h > result.newY) &&
-            // that it wasn't already colliding,
-            (colliderTrans.y + colliderTrans.h <= oldY) &&
-            // that the position on the other axis is in range,
-            (colliderTrans.x + colliderTrans.w > result.newX) &&
-            (colliderTrans.x < result.newX + transformable.w) &&
-            // and that the collider is not farther away than the environmental
-            // boundary.
-            (!boundaryCollision ||
-              (colliderTrans.y + colliderTrans.h >= it->first)))
-        {
-          colliders.push_back(collider);
-        }
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
+
+      // Check if the entity would move into the potential collider,
+      if ((colliderTrans.x < result.newX + transformable.w) &&
+          // that it wasn't already colliding,
+          (colliderTrans.x >= oldRight) &&
+          // that the position on the other axis is in range,
+          (colliderTrans.y + colliderTrans.h > oldY) &&
+          (colliderTrans.y < oldBottom) &&
+          // and that the collider is not farther away than the environmental
+          // boundary.
+          (!boundaryCollision || (colliderTrans.x <= it->first)))
+      {
+        colliders.push_back(collider);
       }
+    }
 
-      std::sort(
-        std::begin(colliders),
-        std::end(colliders),
-        [&] (id_type left, id_type right) {
-          auto& leftTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(left);
+    std::sort(
+      std::begin(colliders),
+      std::end(colliders),
+      [&] (id_type left, id_type right) {
+        auto& leftTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(left);
 
-          auto& rightTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(right);
+        auto& rightTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(right);
 
-          return (rightTrans.y < leftTrans.y);
-        });
+        return (leftTrans.x < rightTrans.x);
+      });
 
-      for (id_type collider : colliders)
-      {
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
+    for (id_type collider : colliders)
+    {
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
 
-        // Check if the entity would still move into the potential collider.
-        if (colliderTrans.y + colliderTrans.h <= result.newY)
-        {
-          break;
-        }
+      // Check if the entity would still move into the potential collider.
+      if (colliderTrans.x >= result.newX + transformable.w)
+      {
+        break;
+      }
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-        processCollision(
-          entity,
-          collider,
-          Direction::up,
-          colliderPonder.colliderType,
-          colliderTrans.y + colliderTrans.h,
-          colliderTrans.x,
-          colliderTrans.x + colliderTrans.w,
-          result);
+      processCollision(
+        entity,
+        collider,
+        Direction::right,
+        colliderPonder.colliderType,
+        colliderTrans.x,
+        colliderTrans.y,
+        colliderTrans.y + colliderTrans.h,
+        result);
 
-        if (result.stopProcessing)
-        {
-          break;
-        }
+      if (result.stopProcessing)
+      {
+        break;
       }
+    }
 
-      // If movement hasn't been stopped by an intermediary object, and
-      // collision checking hasn't been stopped, process the environmental
-      // boundaries closest to the entity.
-      if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
-      {
-        double boundaryAxis = it->first;
+    // If movement hasn't been stopped by an intermediary object, and
+    // collision checking hasn't been stopped, process the environmental
+    // boundaries closest to the entity.
+    if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
+    {
+      double boundaryAxis = it->first;
 
-        for (;
-            (it != std::end(mappable.upBoundaries)) &&
-              (it->first == boundaryAxis);
-            it++)
+      for (;
+          (it != std::end(mappable.rightBoundaries)) &&
+            (it->first == boundaryAxis);
+          it++)
+      {
+        if ((oldBottom > it->second.lower) && (oldY < it->second.upper))
         {
-          if ((result.newX + transformable.w > it->second.lower) &&
-              (result.newX < it->second.upper))
+          processCollision(
+            entity,
+            mapEntity,
+            Direction::right,
+            it->second.type,
+            it->first,
+            it->second.lower,
+            it->second.upper,
+            result);
+
+          if (result.stopProcessing)
           {
-            processCollision(
-              entity,
-              mapEntity,
-              Direction::up,
-              it->second.type,
-              it->first,
-              it->second.lower,
-              it->second.upper,
-              result);
-
-            if (result.stopProcessing)
-            {
-              break;
-            }
+            break;
           }
         }
       }
-    } else if ((!result.stopProcessing) && (result.newY > oldY))
-    {
-      bool boundaryCollision = false;
-      auto it = mappable.downBoundaries.lower_bound(oldBottom);
+    }
+  }
 
-      // Find the axis distance of the closest environmental boundary.
-      for (;
-          (it != std::end(mappable.downBoundaries))
-            && (it->first <= (result.newY + transformable.h));
-          it++)
+  // Find vertical collisions
+  result.touchedWall = false;
+
+  if ((!result.stopProcessing) && (result.newY < oldY))
+  {
+    bool boundaryCollision = false;
+    auto it = mappable.upBoundaries.lower_bound(oldY);
+
+    // Find the axis distance of the closest environmental boundary.
+    for (;
+        (it != std::end(mappable.upBoundaries)) &&
+          (it->first >= result.newY);
+        it++)
+    {
+      // Check that the boundary is in range for the other axis.
+      if ((result.newX + transformable.h > it->second.lower) &&
+          (result.newX < it->second.upper))
       {
-        // Check that the boundary is in range for the other axis.
-        if ((result.newX + transformable.w > it->second.lower) &&
-            (result.newX < it->second.upper))
-        {
-          // We have a collision!
-          boundaryCollision = true;
+        // We have a collision!
+        boundaryCollision = true;
 
-          break;
-        }
+        break;
       }
+    }
 
-      // Find a list of potential colliders, sorted so that the closest is
-      // first.
-      std::vector<id_type> colliders;
+    // Find a list of potential colliders, sorted so that the closest is
+    // first.
+    std::vector<id_type> colliders;
 
-      for (id_type collider : entities)
+    for (id_type collider : entities)
+    {
+      // Can't collide with self.
+      if (collider == entity)
       {
-        // Can't collide with self.
-        if (collider == entity)
-        {
-          continue;
-        }
+        continue;
+      }
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-        // Only check objects that are active.
-        if (!colliderPonder.active)
-        {
-          continue;
-        }
+      // Only check objects that are active.
+      if (!colliderPonder.active)
+      {
+        continue;
+      }
 
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
-
-        // Check if the entity would move into the potential collider,
-        if ((colliderTrans.y < result.newY + transformable.h) &&
-            // that it wasn't already colliding,
-            (colliderTrans.y >= oldBottom) &&
-            // that the position on the other axis is in range,
-            (colliderTrans.x + colliderTrans.w > result.newX) &&
-            (colliderTrans.x < result.newX + transformable.w) &&
-            // and that the collider is not farther away than the environmental
-            // boundary.
-            (!boundaryCollision || (colliderTrans.y <= it->first)))
-        {
-          colliders.push_back(collider);
-        }
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
+
+      // Check if the entity would move into the potential collider,
+      if ((colliderTrans.y + colliderTrans.h > result.newY) &&
+          // that it wasn't already colliding,
+          (colliderTrans.y + colliderTrans.h <= oldY) &&
+          // that the position on the other axis is in range,
+          (colliderTrans.x + colliderTrans.w > result.newX) &&
+          (colliderTrans.x < result.newX + transformable.w) &&
+          // and that the collider is not farther away than the environmental
+          // boundary.
+          (!boundaryCollision ||
+            (colliderTrans.y + colliderTrans.h >= it->first)))
+      {
+        colliders.push_back(collider);
       }
+    }
 
-      std::sort(
-        std::begin(colliders),
-        std::end(colliders),
-        [&] (id_type left, id_type right) {
-          auto& leftTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(left);
+    std::sort(
+      std::begin(colliders),
+      std::end(colliders),
+      [&] (id_type left, id_type right) {
+        auto& leftTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(left);
 
-          auto& rightTrans = game_.getEntityManager().
-            getComponent<TransformableComponent>(right);
+        auto& rightTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(right);
 
-          return (leftTrans.y < rightTrans.y);
-        });
+        return (rightTrans.y < leftTrans.y);
+      });
 
-      for (id_type collider : colliders)
-      {
-        auto& colliderTrans = game_.getEntityManager().
-          getComponent<TransformableComponent>(collider);
+    for (id_type collider : colliders)
+    {
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
 
-        // Check if the entity would still move into the potential collider.
-        if (colliderTrans.y >= result.newY + transformable.h)
-        {
-          break;
-        }
+      // Check if the entity would still move into the potential collider.
+      if (colliderTrans.y + colliderTrans.h <= result.newY)
+      {
+        break;
+      }
 
-        auto& colliderPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(collider);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-        processCollision(
-          entity,
-          collider,
-          Direction::down,
-          colliderPonder.colliderType,
-          colliderTrans.y,
-          colliderTrans.x,
-          colliderTrans.x + colliderTrans.w,
-          result);
+      processCollision(
+        entity,
+        collider,
+        Direction::up,
+        colliderPonder.colliderType,
+        colliderTrans.y + colliderTrans.h,
+        colliderTrans.x,
+        colliderTrans.x + colliderTrans.w,
+        result);
 
-        if (result.stopProcessing)
-        {
-          break;
-        }
+      if (result.stopProcessing)
+      {
+        break;
       }
+    }
 
-      // If movement hasn't been stopped by an intermediary object, and
-      // collision checking hasn't been stopped, process the environmental
-      // boundaries closest to the entity.
-      if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
-      {
-        double boundaryAxis = it->first;
+    // If movement hasn't been stopped by an intermediary object, and
+    // collision checking hasn't been stopped, process the environmental
+    // boundaries closest to the entity.
+    if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
+    {
+      double boundaryAxis = it->first;
 
-        for (;
-            (it != std::end(mappable.downBoundaries)) &&
-              (it->first == boundaryAxis);
-            it++)
+      for (;
+          (it != std::end(mappable.upBoundaries)) &&
+            (it->first == boundaryAxis);
+          it++)
+      {
+        if ((result.newX + transformable.w > it->second.lower) &&
+            (result.newX < it->second.upper))
         {
-          if ((result.newX + transformable.w > it->second.lower) &&
-              (result.newX < it->second.upper))
+          processCollision(
+            entity,
+            mapEntity,
+            Direction::up,
+            it->second.type,
+            it->first,
+            it->second.lower,
+            it->second.upper,
+            result);
+
+          if (result.stopProcessing)
           {
-            processCollision(
-              entity,
-              mapEntity,
-              Direction::down,
-              it->second.type,
-              it->first,
-              it->second.lower,
-              it->second.upper,
-              result);
-
-            if (result.stopProcessing)
-            {
-              break;
-            }
+            break;
           }
         }
       }
     }
+  } else if ((!result.stopProcessing) && (result.newY > oldY))
+  {
+    bool boundaryCollision = false;
+    auto it = mappable.downBoundaries.lower_bound(oldBottom);
+
+    // Find the axis distance of the closest environmental boundary.
+    for (;
+        (it != std::end(mappable.downBoundaries))
+          && (it->first <= (result.newY + transformable.h));
+        it++)
+    {
+      // Check that the boundary is in range for the other axis.
+      if ((result.newX + transformable.w > it->second.lower) &&
+          (result.newX < it->second.upper))
+      {
+        // We have a collision!
+        boundaryCollision = true;
 
-    // Move
-    transformable.x = result.newX;
-    transformable.y = result.newY;
+        break;
+      }
+    }
+
+    // Find a list of potential colliders, sorted so that the closest is
+    // first.
+    std::vector<id_type> colliders;
 
-    // Perform cleanup for orientable entites
-    if (game_.getEntityManager().hasComponent<OrientableComponent>(entity))
+    for (id_type collider : entities)
     {
-      auto& orientable = game_.getEntityManager().
-        getComponent<OrientableComponent>(entity);
+      // Can't collide with self.
+      if (collider == entity)
+      {
+        continue;
+      }
+
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-      // Handle changes in groundedness
-      if (ponderable.grounded != oldGrounded)
+      // Only check objects that are active.
+      if (!colliderPonder.active)
       {
-        if (ponderable.grounded)
-        {
-          game_.getSystemManager().getSystem<OrientingSystem>().land(entity);
-        } else {
-          game_.getSystemManager().
-            getSystem<OrientingSystem>().startFalling(entity);
-        }
+        continue;
       }
 
-      // Complete dropping, if necessary
-      if (orientable.getDropState() == OrientableComponent::DropState::active)
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
+
+      // Check if the entity would move into the potential collider,
+      if ((colliderTrans.y < result.newY + transformable.h) &&
+          // that it wasn't already colliding,
+          (colliderTrans.y >= oldBottom) &&
+          // that the position on the other axis is in range,
+          (colliderTrans.x + colliderTrans.w > result.newX) &&
+          (colliderTrans.x < result.newX + transformable.w) &&
+          // and that the collider is not farther away than the environmental
+          // boundary.
+          (!boundaryCollision || (colliderTrans.y <= it->first)))
       {
-        orientable.setDropState(OrientableComponent::DropState::none);
+        colliders.push_back(collider);
       }
     }
 
-    // Ferry or unferry as necessary
-    if ((ponderable.type == PonderableComponent::Type::freefalling) &&
-        (ponderable.grounded != oldGrounded))
-    {
-      if (ponderable.grounded &&
-          game_.getEntityManager().
-            hasComponent<PonderableComponent>(result.groundEntity))
-      {
-        // The body is now being ferried
-        auto& ferryPonder = game_.getEntityManager().
-          getComponent<PonderableComponent>(result.groundEntity);
+    std::sort(
+      std::begin(colliders),
+      std::end(colliders),
+      [&] (id_type left, id_type right) {
+        auto& leftTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(left);
+
+        auto& rightTrans = game_.getEntityManager().
+          getComponent<TransformableComponent>(right);
 
-        ponderable.ferried = true;
-        ponderable.ferry = result.groundEntity;
+        return (leftTrans.y < rightTrans.y);
+      });
 
-        ferryPonder.passengers.insert(entity);
-      } else if (ponderable.ferried)
+    for (id_type collider : colliders)
+    {
+      auto& colliderTrans = game_.getEntityManager().
+        getComponent<TransformableComponent>(collider);
+
+      // Check if the entity would still move into the potential collider.
+      if (colliderTrans.y >= result.newY + transformable.h)
       {
-        // The body is no longer being ferried
-        unferry(entity);
+        break;
       }
-    }
 
-    // Update a ferry passenger's relative position
-    if (ponderable.ferried)
-    {
-      auto& ferryTrans = game_.getEntityManager().
-        getComponent<TransformableComponent>(ponderable.ferry);
+      auto& colliderPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(collider);
 
-      ponderable.relX = transformable.x - ferryTrans.x;
-      ponderable.relY = transformable.y - ferryTrans.y;
+      processCollision(
+        entity,
+        collider,
+        Direction::down,
+        colliderPonder.colliderType,
+        colliderTrans.y,
+        colliderTrans.x,
+        colliderTrans.x + colliderTrans.w,
+        result);
+
+      if (result.stopProcessing)
+      {
+        break;
+      }
     }
 
-    // Move to an adjacent map, if necessary
-    if (result.adjacentlyWarping)
+    // If movement hasn't been stopped by an intermediary object, and
+    // collision checking hasn't been stopped, process the environmental
+    // boundaries closest to the entity.
+    if (!result.stopProcessing && !result.touchedWall && boundaryCollision)
     {
-      double warpX = result.newX;
-      double warpY = result.newY;
+      double boundaryAxis = it->first;
 
-      switch (result.adjWarpDir)
+      for (;
+          (it != std::end(mappable.downBoundaries)) &&
+            (it->first == boundaryAxis);
+          it++)
       {
-        case Direction::left:
+        if ((result.newX + transformable.w > it->second.lower) &&
+            (result.newX < it->second.upper))
         {
-          warpX = GAME_WIDTH + WALL_GAP - transformable.w;
-
-          break;
+          processCollision(
+            entity,
+            mapEntity,
+            Direction::down,
+            it->second.type,
+            it->first,
+            it->second.lower,
+            it->second.upper,
+            result);
+
+          if (result.stopProcessing)
+          {
+            break;
+          }
         }
+      }
+    }
+  }
 
-        case Direction::right:
-        {
-          warpX = -WALL_GAP;
+  // Move
+  transformable.x = result.newX;
+  transformable.y = result.newY;
 
-          break;
-        }
+  // Perform cleanup for orientable entites
+  if (game_.getEntityManager().hasComponent<OrientableComponent>(entity))
+  {
+    auto& orientable = game_.getEntityManager().
+      getComponent<OrientableComponent>(entity);
 
-        case Direction::up:
-        {
-          warpY = MAP_HEIGHT * TILE_HEIGHT - transformable.h;
+    // Handle changes in groundedness
+    if (ponderable.grounded != oldGrounded)
+    {
+      if (ponderable.grounded)
+      {
+        game_.getSystemManager().getSystem<OrientingSystem>().land(entity);
+      } else {
+        game_.getSystemManager().
+          getSystem<OrientingSystem>().startFalling(entity);
+      }
+    }
 
-          break;
-        }
+    // Complete dropping, if necessary
+    if (orientable.getDropState() == OrientableComponent::DropState::active)
+    {
+      orientable.setDropState(OrientableComponent::DropState::none);
+    }
+  }
 
-        case Direction::down:
-        {
-          warpY = -WALL_GAP;
+  // Ferry or unferry as necessary
+  if ((ponderable.type == PonderableComponent::Type::freefalling) &&
+      (ponderable.grounded != oldGrounded))
+  {
+    if (ponderable.grounded &&
+        game_.getEntityManager().
+          hasComponent<PonderableComponent>(result.groundEntity))
+    {
+      // The body is now being ferried
+      auto& ferryPonder = game_.getEntityManager().
+        getComponent<PonderableComponent>(result.groundEntity);
 
-          break;
-        }
-      }
+      ponderable.ferried = true;
+      ponderable.ferry = result.groundEntity;
 
-      game_.getSystemManager().getSystem<PlayingSystem>().
-        changeMap(
-          entity,
-          result.adjWarpMapId,
-          warpX,
-          warpY);
+      ferryPonder.passengers.insert(entity);
+    } else if (ponderable.ferried)
+    {
+      // The body is no longer being ferried
+      unferry(entity);
     }
   }
-}
 
-void PonderingSystem::initializeBody(
-  id_type entity,
-  PonderableComponent::Type type)
-{
-  auto& ponderable = game_.getEntityManager().
-    emplaceComponent<PonderableComponent>(entity, type);
+  // Update a ferry passenger's relative position
+  if (ponderable.ferried)
+  {
+    auto& ferryTrans = game_.getEntityManager().
+      getComponent<TransformableComponent>(ponderable.ferry);
 
-  if (type == PonderableComponent::Type::freefalling)
+    ponderable.relX = transformable.x - ferryTrans.x;
+    ponderable.relY = transformable.y - ferryTrans.y;
+  }
+
+  // Handle ferry passengers
+  std::set<id_type> passengers = ponderable.passengers;
+
+  for (id_type passenger : passengers)
   {
-    ponderable.accelY = NORMAL_GRAVITY;
+    tickBody(
+      passenger,
+      dt,
+      entities);
   }
-}
 
-void PonderingSystem::initPrototype(id_type prototype)
-{
-  auto& ponderable = game_.getEntityManager().
-    getComponent<PonderableComponent>(prototype);
+  // Move to an adjacent map, if necessary
+  if (result.adjacentlyWarping)
+  {
+    double warpX = result.newX;
+    double warpY = result.newY;
 
-  ponderable.velX = 0.0;
-  ponderable.velY = 0.0;
-  ponderable.accelX = 0.0;
-  ponderable.accelY = 0.0;
-  ponderable.grounded = false;
-  ponderable.frozen = false;
-  ponderable.collidable = true;
-  ponderable.ferried = false;
-  ponderable.passengers.clear();
-}
+    switch (result.adjWarpDir)
+    {
+      case Direction::left:
+      {
+        warpX = GAME_WIDTH + WALL_GAP - transformable.w;
 
-void PonderingSystem::unferry(id_type entity)
-{
-  auto& ponderable = game_.getEntityManager().
-    getComponent<PonderableComponent>(entity);
+        break;
+      }
 
-  if (ponderable.ferried)
-  {
-    ponderable.ferried = false;
+      case Direction::right:
+      {
+        warpX = -WALL_GAP;
 
-    auto& ferryPonder = game_.getEntityManager().
-      getComponent<PonderableComponent>(ponderable.ferry);
+        break;
+      }
 
-    ferryPonder.passengers.erase(entity);
+      case Direction::up:
+      {
+        warpY = MAP_HEIGHT * TILE_HEIGHT - transformable.h;
+
+        break;
+      }
+
+      case Direction::down:
+      {
+        warpY = -WALL_GAP;
+
+        break;
+      }
+    }
+
+    game_.getSystemManager().getSystem<PlayingSystem>().
+      changeMap(
+        entity,
+        result.adjWarpMapId,
+        warpX,
+        warpY);
   }
 }
 
@@ -46,6 +46,11 @@ private:
     id_type groundEntity;
   };
 
+  void tickBody(
+    id_type entity,
+    double dt,
+    const std::set<id_type>& entities);
+
   void processCollision(
     id_type entity,
     id_type collider,