diff --git a/src/defs.h b/src/defs.h
index eb8f172..e99f398 100644
--- a/src/defs.h
+++ b/src/defs.h
@@ -81,18 +81,56 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
 #define MAX_WIDGET_OPTIONS			8
 
-#define ET_ENEMY					0
-#define ET_KEY						1
-#define ET_MIA						2
-#define ET_BOB						3
-#define ET_DESTRUCTABLE				4
-#define ET_BOSS						5
+enum
+{
+	ET_EFFECT, 
+	ET_TRAP, 
+	ET_BOB, 
+	ET_ENEMY, 
+	ET_TEEKA, 
+	ET_BOSS, 
+	ET_HEART_CELL, 
+	ET_KEY, 
+	ET_ITEM, 
+	ET_CONSUMABLE, 
+	ET_MIA, 
+	ET_DECORATION, 
+	ET_DOOR, 
+	ET_LIFT, 
+	ET_PUSHBLOCK, 
+	ET_DESTRUCTABLE, 
+	ET_POWER_POINT, 
+	ET_CARD_READER, 
+	ET_PRESSURE_PLATE, 
+	ET_TELEPORTER, 
+	ET_ITEM_PAD, 
+	ET_POOL, 
+	ET_EXIT, 
+	ET_INFO_POINT
+};
 
-#define EF_NONE						0
-#define EF_HEART_CELL				(2 << 0)
-#define EF_WEIGHTLESS				(2 << 1)
-#define EF_BOMB_SHIELD				(2 << 2)
-#define EF_IMMUNE					(2 << 3)
+#define EF_NONE					0
+#define EF_WEIGHTLESS 			(2 << 0)
+#define EF_BOUNCES				(2 << 1)
+#define EF_TELEPORTING			(2 << 2)
+#define EF_NO_ENVIRONMENT		(2 << 3)
+#define EF_SWIMS				(2 << 4)
+#define EF_HALT_AT_EDGE			(2 << 5)
+#define EF_NO_CLIP				(2 << 6)
+#define EF_EXPLODES				(2 << 7)
+#define EF_IGNORE_BULLETS		(2 << 8)
+#define EF_FLICKER				(2 << 9)
+#define EF_FRICTIONLESS			(2 << 10)
+#define EF_WATER_BREATHING		(2 << 11)
+#define EF_IMMUNE				(2 << 12)
+#define EF_BOMB_SHIELD			(2 << 13)
+#define EF_GONE					(2 << 14)
+#define EF_KILL_OFFSCREEN		(2 << 15)
+#define EF_ALWAYS_PROCESS		(2 << 16)
+#define EF_NO_TELEPORT			(2 << 17)
+
+#define GRAVITY_POWER				0.5f
+#define FRICTION					0.75f
 
 enum
 {
@@ -153,6 +191,11 @@ enum
 	PLANE_FOREGROUND
 };
 
+enum
+{
+	ENV_AIR
+};
+
 enum
 {
 	PT_LINE,
diff --git a/src/structs.h b/src/structs.h
index 6e70c57..49c2173 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -84,6 +84,7 @@ typedef struct {
 } Delegate;
 
 struct Entity {
+	unsigned long uniqueId;
 	char name[MAX_NAME_LENGTH];
 	int type;
 	float x;
@@ -91,9 +92,12 @@ struct Entity {
 	int w;
 	int h;
 	int health;
+	int healthMax;
 	int alive;
 	float dx;
 	float dy;
+	int tx;
+	int ty;
 	int reload;
 	int isOnGround;
 	int facing;
@@ -101,6 +105,11 @@ struct Entity {
 	int weaponType;
 	int shotsToFire;
 	int isSolid;
+	int environment;
+	int isStatic;
+	int isMissionTarget;
+	int thinkTime;
+	int plane;
 	int value;
 	long flags;
 	SDL_Rect bounds;
@@ -219,6 +228,7 @@ typedef struct {
 	int enemiesKilled;
 	int missionsPlayed;
 	long timePlayed;
+	unsigned long entityCounter;
 	char worldId[MAX_NAME_LENGTH];
 	int isResumingMission;
 	int isComplete;
diff --git a/src/world/entities.c b/src/world/entities.c
index 1202cbe..b5f265a 100644
--- a/src/world/entities.c
+++ b/src/world/entities.c
@@ -29,9 +29,116 @@ Entity *createEntity(void)
 	world.entityTail->next = e;
 	world.entityTail = e;
 	
+	e->uniqueId = game.entityCounter++;
+	
 	return e;
 }
 
+void initEntity(Entity *e)
+{
+	e->sprite[0] = e->sprite[1] = e->sprite[2] = -1;
+	
+	e->environment = ENV_AIR;
+	e->alive = ALIVE_ALIVE;
+
+	e->isOnGround = 0;
+	e->isSolid = 0;
+	e->isStatic = 0;
+	e->isMissionTarget = 0;
+
+	e->health = e->healthMax = 1;
+
+	e->facing = FACING_LEFT;
+
+	e->spriteFrame = -1;
+	e->spriteTime = 0;
+
+	e->dx = e->dy = 0;
+
+	e->flags = 0;
+
+	e->owner = NULL;
+
+	e->thinkTime = 0;
+
+	e->plane = PLANE_BACKGROUND;
+}
+
+SDL_Rect *getEntityBounds(Entity *e)
+{
+	e->bounds.x = e->x;
+	e->bounds.y = e->y;
+	e->bounds.w = e->w;
+	e->bounds.h = e->h;
+
+	return &e->bounds;
+}
+
+int getCurrentEntitySprite(Entity *e)
+{
+	return e->sprite[e->facing];
+}
+
+void animateEntity(Entity *e)
+{
+	Sprite *spr;
+	
+	if (e->spriteTime != -1)
+	{
+		e->spriteTime--;
+
+		if (e->spriteTime <= 0)
+		{
+			spr = getSpriteByIndex(getCurrentEntitySprite(e));
+			e->spriteFrame = wrap(e->spriteFrame + 1, 0, 1);
+			e->spriteTime = 0;
+			e->w = spr->w;
+			e->h = spr->h;
+		}
+	}
+}
+
+void setEntitySize(Entity *e)
+{
+	Sprite *spr;
+	
+	spr = getSpriteByIndex(getCurrentEntitySprite(e));
+	e->w = spr->w;
+	e->h = spr->h;
+}
+
+float bounce(Entity *e, float x)
+{
+	if (!(e->flags & EF_BOUNCES))
+	{
+		return 0;
+	}
+	else if (e->flags & EF_FRICTIONLESS)
+	{
+		return -x;
+	}
+
+	x = -x * FRICTION;
+
+	if (x > -1 && x < 1)
+	{
+		e->flags &= ~EF_BOUNCES;
+		x = 0;
+	}
+
+	return x;
+}
+
+void teleport(Entity *e, float tx, float ty)
+{
+	e->tx = tx;
+	e->ty = ty;
+
+	e->flags |= EF_TELEPORTING;
+
+	addTeleportStars(e);
+}
+
 void activateEntities(char *names, int activate)
 {
 }
diff --git a/src/world/entities.h b/src/world/entities.h
index 20cd098..8417d02 100644
--- a/src/world/entities.h
+++ b/src/world/entities.h
@@ -20,4 +20,9 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
 #include "../common.h"
 
+extern Sprite *getSpriteByIndex(int x);
+extern float wrap(float value, float low, float high);
+extern void addTeleportStars(Entity *e);
+
+extern Game game;
 extern World world;
diff --git a/src/world/objectives.c b/src/world/objectives.c
index cbae88c..cc33397 100644
--- a/src/world/objectives.c
+++ b/src/world/objectives.c
@@ -173,7 +173,7 @@ static int isMissingHeartCell(char *targetName)
 	{
 		if (e->alive == ALIVE_ALIVE)
 		{
-			if (e->flags & EF_HEART_CELL)
+			if (e->type == ET_HEART_CELL)
 			{
 				return 0;
 			}