diff --git a/README.gmi b/README.gmi
index d1b5dd3..815f69f 100644
--- a/README.gmi
+++ b/README.gmi
@@ -1,7 +1,7 @@
 # Simworld Lite
 Simworld is a zero-player game in which players create simulated environments and ecosystems that run with no user intervention. The environments and the creatures that inhabit them are all completely defined through user-created mods. Though there's no real goal to the game, a good challenge is to create ecosystems that are self-sustaining and can thus run indefinitely.
 
-Note: I'm not galaxy-brained enough to do the full idea at the moment, so this is the "lite" version, contianing only the bare minimum to make the idea work.
+Note: I'm not galaxy-brained enough to do the full idea at the moment, so this is the "lite" version, containing only the bare minimum to make the idea work.
 
 ## Build from Source
 ### Dependencies
diff --git a/build.sh b/build.sh
index ef09b6d..01f931d 100755
--- a/build.sh
+++ b/build.sh
@@ -29,10 +29,8 @@ mkdir -p build
 cd build || exit
 
 if [ ${debug} -eq 1 ]; then
-    echo debug
     cmake -DCMAKE_BUILD_TYPE=debug ..
 else
-    echo release
     cmake -DCMAKE_BUILD_TYPE=release ..
 fi
 
diff --git a/src/entity/entity.c b/src/entity/entity.c
new file mode 100644
index 0000000..7fbfa51
--- /dev/null
+++ b/src/entity/entity.c
@@ -0,0 +1,13 @@
+// entity/entity.c
+
+#include <assert.h>
+
+#include "entity.h"
+
+void entity_init(struct entity_t *self, size_t id, size_t x, size_t y) {
+    assert(self != NULL);
+
+    self->id = id;
+    self->x = x;
+    self->y = y;
+}
diff --git a/src/entity/entity.h b/src/entity/entity.h
new file mode 100644
index 0000000..d3042d2
--- /dev/null
+++ b/src/entity/entity.h
@@ -0,0 +1,14 @@
+#ifndef ENTITY_ENTITY_H
+#define ENTITY_ENTITY_H
+
+#include <stdlib.h>
+
+struct entity_t {
+    size_t id;
+    size_t x;
+    size_t y;
+};
+
+void entity_init(struct entity_t *, size_t, size_t, size_t);
+
+#endif
diff --git a/src/entity/registry.c b/src/entity/registry.c
new file mode 100644
index 0000000..af9d175
--- /dev/null
+++ b/src/entity/registry.c
@@ -0,0 +1,79 @@
+// entity/registry.c
+
+#include <assert.h>
+#include <string.h>
+
+#include "registry.h"
+
+#define MAX_NAME_LENGTH 32
+
+enum error_t entity_registrant_init(
+    struct entity_registrant_t *self,
+    const char *name, char tile
+) {
+    assert(self != NULL);
+
+    if (name == NULL || strlen(name) > MAX_NAME_LENGTH) return ERR_INPUT;
+
+    const char *dup = strndup(name, MAX_NAME_LENGTH);
+    if (dup == NULL) return ERR_ALLOC;
+
+    self->name = dup;
+    self->tile = tile;
+
+    return ERR_OK;
+}
+
+void entity_registrant_free(struct entity_registrant_t *self) {
+    assert (self != NULL);
+
+    free((void *)self->name);
+}
+
+
+enum error_t entity_registry_init(struct entity_registry_t *self) {
+    assert(self != NULL);
+
+    self->size = 1;
+
+    struct entity_registrant_t *entities = calloc(
+        self->size, sizeof(struct entity_registrant_t)
+    );
+
+    if (entities == NULL) return ERR_ALLOC;
+
+    struct entity_registrant_t null_entity;
+    entity_registrant_init(&null_entity, "NULL", '0');
+
+    entities[0] = null_entity;
+
+    self->entities = entities;
+    return ERR_OK;
+}
+
+void entity_registry_free(struct entity_registry_t *self) {
+    assert(self != NULL);
+
+    for (size_t i = 0; i < self->size; i++)
+        entity_registrant_free(&self->entities[i]);
+
+    free(self->entities);
+}
+
+enum error_t entity_registry_append(
+    struct entity_registry_t *self,
+    struct entity_registrant_t *registrant
+) {
+    assert(self != NULL && registrant != NULL);
+
+    self->size += 1;
+    self->entities = reallocarray(
+        self->entities, self->size,
+        sizeof(struct entity_registrant_t)
+    );
+
+    if (self->entities == NULL) return ERR_ALLOC;
+
+    self->entities[self->size - 1] = *registrant;
+    return ERR_OK;
+}
diff --git a/src/entity/registry.h b/src/entity/registry.h
new file mode 100644
index 0000000..9cadf8b
--- /dev/null
+++ b/src/entity/registry.h
@@ -0,0 +1,34 @@
+#ifndef ENTITY_REGISTRY_H
+#define ENTITY_REGISTRY_H
+
+#include <stdlib.h>
+
+#include "../error.h"
+
+struct entity_registrant_t {
+    const char *name;
+    char tile;
+};
+
+enum error_t entity_registrant_init(
+    struct entity_registrant_t *,
+    const char *, char
+);
+
+void entity_registrant_free(struct entity_registrant_t *);
+
+
+struct entity_registry_t {
+    struct entity_registrant_t *entities;
+    size_t size;
+};
+
+enum error_t entity_registry_init(struct entity_registry_t *);
+void entity_registry_free(struct entity_registry_t *);
+
+enum error_t entity_registry_append(
+    struct entity_registry_t *,
+    struct entity_registrant_t *
+);
+
+#endif
diff --git a/src/error.c b/src/error.c
new file mode 100644
index 0000000..5a6e401
--- /dev/null
+++ b/src/error.c
@@ -0,0 +1,15 @@
+// error.c
+
+#include "error.h"
+
+const char *ERROR_STRS[] = {
+    "SUCCESS",
+    "BAD INPUT",
+    "ALLOCATION",
+    "NOT FOUND",
+};
+
+_Static_assert(
+    __ERR_COUNT == (sizeof(ERROR_STRS) / sizeof(ERROR_STRS[0])),
+    "len(ERROR_STRS) must match __ERR_COUNT"
+);
diff --git a/src/error.h b/src/error.h
new file mode 100644
index 0000000..7ffbda8
--- /dev/null
+++ b/src/error.h
@@ -0,0 +1,14 @@
+#ifndef ERROR_H
+#define ERROR_H
+
+enum error_t {
+    ERR_OK,
+    ERR_INPUT,
+    ERR_ALLOC,
+    ERR_NOTFOUND,
+    __ERR_COUNT,
+};
+
+extern const char *ERROR_STRS[];
+
+#endif
diff --git a/src/main.c b/src/main.c
index ab3a851..823a35a 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2,7 +2,29 @@
 
 #include <stdio.h>
 
+#include "world.h"
+
 int main(void) {
-    puts("Hello, world!");
+    enum error_t err = ERR_OK;
+
+    struct world_t world;
+    err = world_init(&world, 10, 10);
+    if (err != ERR_OK) goto error;
+
+    err = world_register_entity(&world, "john", 'j');
+    if (err != ERR_OK) goto error_register;
+
+    err = world_place_entity(&world, 1, 1, 2);
+    if (err != ERR_OK) goto error_register;
+
+    world_print(&world);
+
+    world_free(&world);
     return 0;
+
+error_register:
+    world_free(&world);
+error:
+    printf("ERROR: %s", ERROR_STRS[err]);
+    exit(err);
 }
diff --git a/src/world.c b/src/world.c
new file mode 100644
index 0000000..0c08c9d
--- /dev/null
+++ b/src/world.c
@@ -0,0 +1,79 @@
+// world.c
+
+#include <assert.h>
+#include <string.h>
+
+#include "world.h"
+
+enum error_t world_init(struct world_t *self, size_t height, size_t width) {
+    assert(self != NULL);
+
+    self->height = height;
+    self->width = width;
+
+    memset(self->entities, 0, MAX_ENTITIES * sizeof(struct entity_t));
+
+    enum error_t err = entity_registry_init(&self->registered_entities);
+    if (err != ERR_OK) return err;
+
+    return ERR_OK;
+}
+
+void world_free(struct world_t *self) {
+    entity_registry_free(&self->registered_entities);
+}
+
+enum error_t world_register_entity(
+    struct world_t *self,
+    const char *name, char tile
+) {
+    enum error_t err;
+    struct entity_registry_t *registry = &self->registered_entities;
+
+    struct entity_registrant_t registrant;
+    err = entity_registrant_init(&registrant, name, tile);
+    if (err != ERR_OK) return err;
+
+    err = entity_registry_append(registry, &registrant);
+    if (err != ERR_OK) return err;
+
+    return ERR_OK;
+}
+
+static size_t world_find_empty_entity(struct world_t *self) {
+    for (size_t i = 0; i < MAX_ENTITIES; i++)
+        if (self->entities[i].id == 0) return i;
+
+    return MAX_ENTITIES;
+}
+
+enum error_t world_place_entity(
+    struct world_t *self,
+    size_t id, size_t x, size_t y
+) {
+    assert(self != NULL);
+
+    size_t i = world_find_empty_entity(self);
+    if (i == MAX_ENTITIES) return ERR_NOTFOUND;
+
+    entity_init(&self->entities[i], id, x, y);
+
+    return ERR_OK;
+}
+
+#include <stdio.h>
+void world_print(struct world_t *self) {
+    for (size_t i = 0; i < MAX_ENTITIES; i++) {
+        struct entity_t *entity = &self->entities[i];
+        struct entity_registrant_t *registrant =
+            &self->registered_entities.entities[entity->id];
+
+        if (entity->id == 0) continue;
+
+        printf("%zu (%s): (%zu,%zu) '%c'\n",
+            entity->id, registrant->name,
+            entity->x, entity->y,
+            registrant->tile
+        );
+    }
+}
diff --git a/src/world.h b/src/world.h
new file mode 100644
index 0000000..d855d12
--- /dev/null
+++ b/src/world.h
@@ -0,0 +1,28 @@
+#ifndef WORLD_H
+#define WORLD_H
+
+#include <stdlib.h>
+
+#include "error.h"
+#include "entity/registry.h"
+#include "entity/entity.h"
+
+#define MAX_ENTITIES 256
+
+struct world_t {
+    struct entity_t entities[MAX_ENTITIES];
+    struct entity_registry_t registered_entities;
+
+    size_t height;
+    size_t width;
+};
+
+enum error_t world_init(struct world_t *, size_t, size_t);
+void world_free(struct world_t *);
+
+enum error_t world_register_entity(struct world_t *, const char *, char);
+enum error_t world_place_entity(struct world_t *, size_t, size_t, size_t);
+
+void world_print(struct world_t *);
+
+#endif