diff --git a/common/include/error.h b/common/include/error.h
index 7a231a1..3201608 100644
--- a/common/include/error.h
+++ b/common/include/error.h
@@ -1,6 +1,10 @@
 #ifndef ERROR_H
 #define ERROR_H
 
+// TODO: Most of these aren't even errors used in this library.
+// I should trim this down to only the ones belonging to the library, and make
+// new enums for the client and server. Perhaps I can leverage __ERR_COUNT to
+// have the client/server-specific enums start where this one ends
 enum error_t {
     ERR_OK,
     ERR_INPUT,
@@ -14,6 +18,7 @@ enum error_t {
     ERR_INVALID_REQUEST,
     ERR_REQUEST_FAILED,
     ERR_THREAD,
+    ERR_MUTEX,
     __ERR_COUNT,
 };
 
diff --git a/common/src/error.c b/common/src/error.c
index 988768d..5a77a82 100644
--- a/common/src/error.c
+++ b/common/src/error.c
@@ -14,7 +14,8 @@ char const *const ERROR_STRS[] = {
     "JSON DESERIALISATION",
     "INVALID REQUEST",
     "REQUEST FAILED",
-    "THREAD INITIALISATION"
+    "THREAD INITIALISATION",
+    "MUTEX ERROR",
 };
 
 
diff --git a/server/src/main.c b/server/src/main.c
index 8cd5ad0..db985ba 100644
--- a/server/src/main.c
+++ b/server/src/main.c
@@ -1,5 +1,6 @@
 // main.c
 
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
@@ -23,6 +24,34 @@ static void handle_signal(int signal_no) {
 }
 
 
+static enum error_t simulation_thread_body(struct game_data_t *data) {
+    assert(data != NULL);
+
+    // TODO: An actual game loop lol
+    printf("Hello, world!\n");
+
+    return ERR_OK;
+}
+
+
+
+static enum error_t simulation_thread(
+    pthread_t *pthread,
+    struct game_data_t *data
+) {
+    assert(pthread != NULL);
+    assert(data != NULL);
+
+    int err = pthread_create(
+        pthread, NULL,
+        (void *(*)(void *))simulation_thread_body, data
+    );
+    if (err != 0) return ERR_THREAD;
+
+    return ERR_OK;
+}
+
+
 int main(int argc, char **argv) {
     // Set up variables
     enum error_t err = ERR_OK;
@@ -60,11 +89,18 @@ int main(int argc, char **argv) {
     entity_init(&data.world.entities[26], 2, 2, 6);
         // Make a gap in the entity array to see if "ghost" entities remain
 
-    // Socket handling
+    // Socket handler thread
     pthread_t pthread_socket;
     err = socket_thread(&pthread_socket, &data);
     if (err) goto handle_error;
 
+    // Simulation thread
+    pthread_t pthread_simulation;
+    err = simulation_thread(&pthread_simulation, &data);
+    if (err) goto handle_error;
+
+    // Join threads
+    // TODO: A way to shut down the program properly
     pthread_join(pthread_socket, (void **)&err); // No way this is correct lol
     if (err) goto handle_error;
 
diff --git a/server/src/request.c b/server/src/request.c
index d0f1c08..c5865a6 100644
--- a/server/src/request.c
+++ b/server/src/request.c
@@ -4,10 +4,18 @@
 
 #include "request.h"
 
+static struct response_t response_failure(
+    struct request_t const *request
+) {
+    assert(request != NULL);
+
+    return (struct response_t){ request->type, false, NULL };
+}
+
 static void handle_request_get_world_data(
     struct response_t *response,
     struct request_t const *request,
-    struct game_data_t const *ctx
+    struct game_data_t *ctx
 ) {
     assert(response != NULL);
     assert(request != NULL);
@@ -16,11 +24,24 @@ static void handle_request_get_world_data(
     // TODO: World creation isn't set up yet, so the world-id parameter isn't
     // useful right now, but make sure to use it later when it is set up
 
-    struct response_body_get_world_data_t *body = response->body;
+    struct response_body_get_world_data_t *body =
+        malloc(sizeof(struct response_body_get_world_data_t));
+    if (body == NULL) goto error;
+
+    response->body = body;
+
+    if (pthread_mutex_lock(&ctx->world_lock) != 0) goto error;
     body->world = ctx->world;
+    if (pthread_mutex_unlock(&ctx->world_lock) != 0) goto error;
 
     response->type = request->type;
     response->success = true;
+
+    return;
+
+error:
+    free(body);
+    *response = response_failure(request);
 }
 
 
@@ -35,14 +56,10 @@ struct response_t handle_request(
 
     switch (request->type) {
         case REQUEST_GET_WORLD_DATA:
-            response.body = malloc(sizeof(struct response_body_get_world_data_t));
-            if (response.body == NULL)
-                return (struct response_t){ request->type, false, NULL };
-
             handle_request_get_world_data(&response, request, ctx);
             return response;
 
         default:
-            return (struct response_t){ 0 };
+            return response_failure(request);
     }
 }
diff --git a/server/src/socket.c b/server/src/socket.c
index e35d98b..4f19476 100644
--- a/server/src/socket.c
+++ b/server/src/socket.c
@@ -67,14 +67,12 @@ static enum error_t socket_handle(struct game_data_t *data) {
 }
 
 
-static void *socket_thread_body(void *data_void) {
-    assert(data_void != NULL);
-
-    struct game_data_t *data = (struct game_data_t *)data_void;
+static enum error_t socket_thread_body(struct game_data_t *data) {
+    assert(data != NULL);
 
     enum error_t err = ERR_OK;
 
-    if ((err = socket_init(&data->socket))) return (void *)err;
+    if ((err = socket_init(&data->socket))) return err;
 
     for (int sock_accept;;) {
         if ((sock_accept = accept(data->socket, NULL, NULL)) < 0) {
@@ -95,12 +93,19 @@ error_pre:
 
 error:
     socket_free(&data->socket);
-    return (void *)err;
+    return err;
 }
 
 
 enum error_t socket_thread(pthread_t *pthread, struct game_data_t *data) {
-    int err = pthread_create(pthread, NULL, socket_thread_body, data);
+    assert(pthread != NULL);
+    assert(data != NULL);
+
+    int err = pthread_create(
+        pthread, NULL,
+        (void *(*)(void *))socket_thread_body, // I want to cry tf is this
+        data
+    );
     if (err != 0) return ERR_THREAD;
 
     return ERR_OK;