diff --git a/crates/lang/src/ast.rs b/crates/lang/src/ast.rs
index 42d160c..d5838a2 100644
--- a/crates/lang/src/ast.rs
+++ b/crates/lang/src/ast.rs
@@ -1,6 +1,8 @@
 use crate::lst_parser::syntax_kind::SyntaxKind::*;
 use crate::SyntaxNode;
 use rowan::Language;
+
+// Heavily modified version of https://github.com/rust-analyzer/rowan/blob/e2d2e93e16c5104b136d0bc738a0d48346922200/examples/s_expressions.rs#L250-L266
 macro_rules! ast_nodes {
     ($($ast:ident, $kind:ident);+) => {
         $(
diff --git a/crates/lang/src/world.rs b/crates/lang/src/world.rs
index 2ce9997..7713422 100644
--- a/crates/lang/src/world.rs
+++ b/crates/lang/src/world.rs
@@ -1,5 +1,7 @@
 use std::path::Path;
 
+use self::files::{Files, OpenFileError};
+
 mod error;
 mod files;
 
@@ -7,8 +9,19 @@ struct World;
 
 impl World {
     pub fn new(entry_point: &Path) -> Result<Self, WorldCreationError> {
+        let mut files = Files::default();
+        let (entry_point_id, errors) = files.add_file(entry_point)?;
+
         todo!()
     }
 }
 
-enum WorldCreationError {}
+enum WorldCreationError {
+    FailedToOpenEntryPoint(OpenFileError),
+}
+
+impl From<OpenFileError> for WorldCreationError {
+    fn from(value: OpenFileError) -> Self {
+        Self::FailedToOpenEntryPoint(value)
+    }
+}
diff --git a/crates/lang/src/world/files.rs b/crates/lang/src/world/files.rs
index 0c112ad..24053d7 100644
--- a/crates/lang/src/world/files.rs
+++ b/crates/lang/src/world/files.rs
@@ -15,7 +15,8 @@ use crate::{
     world::{error::Error, files::source_file::SourceFile},
 };
 
-struct Files {
+#[derive(Default)]
+pub struct Files {
     inner: Vec<source_file::SourceFile>,
     path_to_id_map: HashMap<PathBuf, FileId>,
 }