diff --git a/src/main.zig b/src/main.zig
index 763bc7b..df4429f 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -14,20 +14,21 @@ pub fn main() anyerror!void {
     return sys.runGraphics(anyerror, run);
 }
 
-fn run(event_loop: *sys.EventLoop, graphics: *sys.GraphicalContext) anyerror!void {
-    var gpa = std.heap.GeneralPurposeAllocator(){};
+fn run(event_loop: *sys.EventLoop, graphics: *sys.GraphicsContext) anyerror!void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
 
     {
-        const file = event_loop.open(.readonly, sys.Path.get(.data, &.{"ona.lua"}));
+        const file_access =
+            try event_loop.open(.readonly, try sys.FileSystem.data.pathJoin(&.{"data", "ona.lua"}));
 
-        defer _ = event_loop.closeFile(file);
+        defer _ = event_loop.close(file_access);
 
-        const file_size = try file.size(event_loop);
+        const file_size = try file_access.size(event_loop);
         var buffer = try gpa.allocator().alloc(u8, file_size);
 
-        if (try event_loop.readFile(buffer) != file_size) return error.ScriptLoadError;
+        if ((try event_loop.readFile(file_access, buffer)) != file_size) return error.ScriptLoadError;
 
-        sys.log(buffer);
+        event_loop.log(buffer);
     }
 
     while (graphics.poll()) |_| {
diff --git a/src/sys.zig b/src/sys.zig
index 83e8b19..9cae5bf 100644
--- a/src/sys.zig
+++ b/src/sys.zig
@@ -10,8 +10,136 @@ const std = @import("std");
 ///
 ///
 ///
-pub const EventLoop = struct {
+pub const EventLoop = opaque {
+    const Implementation = struct {
+        current_message: ?*Message,
+    };
 
+    ///
+    ///
+    ///
+    const Message = struct {
+        next: ?*Message,
+        frame: anyframe,
+
+        request: union(enum) {
+            open: struct {
+                mode: OpenMode,
+                path: *const FileSystem.Path,
+            },
+        },
+
+        response: union(enum) {
+            none,
+            file_access: *FileAccess,
+            file_error: FileError,
+        } = .none,
+    };
+
+    ///
+    ///
+    ///
+    pub const OpenError = error {
+        NotFound,
+    };
+
+    ///
+    ///
+    ///
+    pub const OpenMode = enum {
+        readonly,
+        overwrite,
+        append,
+    };
+
+    ///
+    ///
+    ///
+    pub fn close(event_loop: *EventLoop, file_access: *FileAccess) void {
+        var message = Message{
+            .frame = @frame(),
+
+            .request = .{
+                .close = .{
+                    .file_access = file_access,
+                },
+            },
+        };
+
+        suspend event_loop.enqueueMessage(&message);
+    }
+
+    ///
+    ///
+    ///
+    fn enqueueMessage(event_loop: *EventLoop, message: *Message) void {
+        const implementation =
+            @ptrCast(*Implementation, @alignCast(@alignOf(Implementation), event_loop));
+
+        if (implementation.current_message) |current_message| {
+            current_message.next = message;
+        } else {
+            implementation.current_message = message;
+        }
+    }
+
+    pub fn log(event_loop: *EventLoop, message: []const u8) void {
+        // TODO: Implement.
+        _ = event_loop;
+        _ = message;
+    }
+
+    ///
+    ///
+    ///
+    pub fn open(event_loop: *EventLoop, mode: OpenMode,
+        path: FileSystem.Path) OpenError!*FileAccess {
+
+        var message = Message{
+            .frame = @frame(),
+
+            .request = .{
+                .open = .{
+                    .mode = mode,
+                    .path = &path,
+                },
+            },
+        };
+
+        suspend event_loop.enqueueMessage(&message);
+
+        switch (message.response) {
+            .file_access => |file_access| return file_access,
+            .open_error => |open_error| return open_error,
+            else => unreachable,
+        }
+    }
+
+    ///
+    ///
+    ///
+    pub fn readFile(event_loop: *EventLoop, file_access: *FileAccess,
+        buffer: []const u8) FileError!usize {
+
+        var message = Message{
+            .frame = @frame(),
+
+            .request = .{
+                .read_file = .{
+                    .file_access = file_access,
+                    .buffer = buffer,
+                },
+            },
+        };
+
+        suspend event_loop.enqueueMessage(&message);
+
+        switch (message.response) {
+            .size => |size| return size,
+            .file_error => |file_error| return file_error,
+            else => unreachable,
+        }
+    }
 };
 
 ///
@@ -23,13 +151,15 @@ pub const FileAccess = opaque {
     /// its byte size or a [FileError] if it failed.
     ///
     pub fn size(file_access: *FileAccess, event_loop: *EventLoop) FileError!usize {
-        const origin_cursor = try app.tellFile(file_access);
+        // Save cursor to return to it later.
+        const origin_cursor = try event_loop.tellFile(file_access);
 
-        try app.seekFile(file_access, .tail, 0);
+        try event_loop.seekFile(file_access, .tail, 0);
 
-        const ending_cursor = try app.tellFile(file_access);
+        const ending_cursor = try event_loop.tellFile(file_access);
 
-        try app.seekFile(file_access, .head, origin_cursor);
+        // Return to original cursor.
+        try event_loop.seekFile(file_access, .head, origin_cursor);
 
         return ending_cursor;
     }
@@ -45,135 +175,194 @@ pub const FileError = error {
 };
 
 ///
-/// Platform-agnostic mechanism for accessing files on any of the virtual file-systems supported by
-/// Ona.
 ///
-pub const Path = struct {
-    length: u16,
-    buffer: [max]u8,
+///
+pub const FileSystem = enum {
+    data,
+    user,
 
     ///
+    /// Platform-agnostic mechanism for referencing files and directories on a [FileSystem]
     ///
+    pub const Path = struct {
+        file_system: FileSystem,
+        length: u16,
+        buffer: [max]u8,
+
+        ///
+        /// Returns `true` if the length of `path` is empty, otherwise `false`.
+        ///
+        pub fn isEmpty(path: Path) bool {
+            return (path.length == 0);
+        }
+
+        ///
+        /// Returns `true` if `this` is equal to `that`, otherwise `false`.
+        ///
+        pub fn equals(this: Path, that: Path) bool {
+            return std.mem.eql(u8, this.buffer[0 .. this.length], that.buffer[0 .. that.length]);
+        }
+
+        ///
+        /// The maximum possible byte-length of a [Path].
+        ///
+        /// Note that paths are encoded using UTF-8, meaning that a character may be bigger than one
+        /// byte. Because of this, it is not safe to asume that a path may hold [max] individual
+        /// characters.
+        ///
+        pub const max = 1000;
+
+        ///
+        ///
+        ///
+        pub fn write(path: Path, writer: io.Writer) bool {
+            return (writer.write(path.buffer[0 .. path.length]) == path.length);
+        }
+    };
+
     ///
-    pub const Error = error {
+    /// [PathError.TooLong] occurs when creating a path that is greater than the maximum size **in
+    /// bytes**.
+    ///
+    pub const PathError = error {
         TooLong,
     };
 
     ///
+    /// Creates and returns a [Path] value in the file system to the location specified by the
+    /// joining of the `component_groups` path values.
     ///
-    ///
-    pub fn isComplete(path: Path) bool {
-        return (path.length != 0) and (path.buffer[0] == '/');
-    }
-
-    ///
-    /// Returns `true` if the length of `path` is empty, otherwise `false`.
-    ///
-    pub fn isEmpty(path: Path) bool {
-        return (path.length == 0);
-    }
-
-    ///
-    /// Returns `true` if `this` is equal to `that`, otherwise `false`.
-    ///
-    pub fn equals(this: Path, that: Path) bool {
-        return std.mem.eql(u8, this.buffer[0 .. this.length], that.buffer[0 .. that.length]);
-    }
-
-    ///
-    /// Creates and returns a [Path] value in the file system indicated by `file_system` from the
-    /// path components in `component_groups`.
-    ///
-    pub fn from(file_system: FileSystem, component_groups: []const []const u8) Error!Path {
+    pub fn pathJoin(file_system: FileSystem, component_groups: []const []const u8) PathError!Path {
         var path = Path{
             .file_system = file_system,
-            .buffer = std.mem.zeroes([max]u8),
+            .buffer = std.mem.zeroes([Path.max]u8),
             .length = 0,
         };
 
-        for (component_groups) |first_component_group,
-            first_component_group_index| if (first_component_group.len != 0) {
-
-            var first_component_root_offset = @as(usize, 0);
-
-            if (component_group[0] == '/') {
-                comptime if (max < 1) unreachable;
-
-                path.buffer[path.length] = '/';
-                path.length += 1;
-                first_component_root_offset = 1;
-            }
-
-            var first_components = mem.Spliterator(u8){
-                .source = first_component_group[first_component_root_offset ..
-                    (first_component_group.len - first_component_root_offset)],
-
+        for (component_groups) |component_group| if (component_group.len != 0) {
+            var components = mem.Spliterator(u8){
+                .source = component_group,
                 .delimiter = "/",
             };
 
-            while (first_components.next()) |component| if (component.len != 0) {
+            while (components.next()) |component| if (component.len != 0) {
                 for (component) |byte| {
-                    if (path.length == max) return error.TooLong;
+                    if (path.length == Path.max) return error.TooLong;
 
                     path.buffer[path.length] = byte;
                     path.length += 1;
                 }
 
-                if (path.length == max) return error.TooLong;
+                if (path.length == Path.max) return error.TooLong;
 
                 path.buffer[path.length] = '/';
                 path.length += 1;
             };
-
-            const second_component_group_index = (first_component_group_index + 1);
-
-            for (component_groups[second_component_group_index .. (component_groups.len -
-                second_component_group_index)]) |component_group| if (component_group.len != 0) {
-
-                var components = mem.Spliterator(u8){
-                    .source = component_group,
-                    .delimiter = "/",
-                };
-
-                while (components.next()) |component| if (component.len != 0) {
-                    for (component) |byte| {
-                        if (path.length == max) return error.TooLong;
-
-                        path.buffer[path.length] = byte;
-                        path.length += 1;
-                    }
-
-                    if (path.length == max) return error.TooLong;
-
-                    path.buffer[path.length] = '/';
-                    path.length += 1;
-                };
-            };
         };
 
         return path;
     }
-
-    ///
-    /// The maximum possible byte-length of a [Path].
-    ///
-    /// Note that paths are encoded using UTF-8, meaning that a character may be bigger than one
-    /// byte. Because of this, it is not safe to asume that a path may hold [max] individual
-    /// characters.
-    ///
-    pub const max = 1000;
-
-    ///
-    ///
-    ///
-    pub fn write(path: Path, writer: io.Writer) bool {
-        return (writer.write(path.buffer[0 .. path.length]) == path.length);
-    }
 };
 
 ///
 ///
 ///
-pub fn runGraphics(comptime ErrorUnion: anytype, run: fn (*App) ErrorUnion!void) void {
+pub const GraphicsContext = opaque {
+    ///
+    ///
+    ///
+    pub const Event = struct {
 
+    };
+
+    const Implementation = struct {
+        event: Event,
+    };
+
+    ///
+    ///
+    ///
+    pub fn poll(graphics_context: *GraphicsContext) ?*const Event {
+        // TODO: Implement.
+        _ = graphics_context;
+
+        return null;
+    }
+
+    ///
+    ///
+    ///
+    pub fn present(graphics_context: *GraphicsContext) void {
+        // TODO: Implement;
+        _ = graphics_context;
+    }
+};
+
+///
+///
+///
+pub fn GraphicsRunner(comptime Errors: type) type {
+    return fn (*EventLoop, *GraphicsContext) Errors!void;
+}
+
+///
+///
+///
+pub fn runGraphics(comptime Errors: anytype, run: GraphicsRunner(Errors)) Errors!void {
+    if (ext.SDL_Init(ext.SDL_INIT_EVERYTHING) != 0) {
+        ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to initialize SDL2 runtime");
+
+        return error.InitFailure;
+    }
+
+    defer ext.SDL_Quit();
+
+    const pref_path = create_pref_path: {
+        const path = ext.SDL_GetPrefPath("ona", "ona") orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to load user path");
+
+            return error.InitFailure;
+        };
+
+        break: create_pref_path path[0 .. std.mem.len(path)];
+    };
+
+    defer ext.SDL_free(pref_path.ptr);
+
+    const window = create_window: {
+        const pos = ext.SDL_WINDOWPOS_UNDEFINED;
+        var flags = @as(u32, 0);
+
+        break: create_window ext.SDL_CreateWindow("Ona", pos, pos, 640, 480, flags) orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to load SDL2 window");
+
+            return error.InitFailure;
+        };
+    };
+
+    defer ext.SDL_DestroyWindow(window);
+
+    const renderer = create_renderer: {
+        var flags = @as(u32, 0);
+
+        break: create_renderer ext.SDL_CreateRenderer(window, -1, flags) orelse {
+            ext.SDL_LogCritical(ext.SDL_LOG_CATEGORY_APPLICATION, "Failed to load SDL2 renderer");
+
+            return error.InitFailure;
+        };
+    };
+
+    defer ext.SDL_DestroyRenderer(renderer);
+
+    var event_loop = EventLoop.Implementation{
+        .current_message = null,
+    };
+
+    var graphics_context = GraphicsContext.Implementation{
+        .event = .{
+
+        },
+    };
+
+    return run(@ptrCast(*EventLoop, &event_loop), @ptrCast(*GraphicsContext, &graphics_context));
 }