diff --git a/src/bin/example.rs b/src/bin/example.rs
index a99d840..6486f63 100644
--- a/src/bin/example.rs
+++ b/src/bin/example.rs
@@ -19,11 +19,13 @@ use sdl2::controller::{GameController, Button, Axis};
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
 use sdl2::rect::Rect;
-use sdl2::render::{TextureCreator, WindowCanvas};
-use sdl2::video::WindowContext;
+use sdl2::render::WindowCanvas;
 
 struct MyEmulator {
     retro: retro::wrapper::LibretroWrapper,
+    core_path: PathBuf,
+    sys_path: Option<PathBuf>,
+
     sys_info: SystemInfo,
     av_info: SystemAvInfo,
 
@@ -32,7 +34,6 @@ struct MyEmulator {
     // video bits
     canvas: WindowCanvas,
     pixel_format: sdl2::pixels::PixelFormatEnum,
-    texture_creator: TextureCreator<WindowContext>,
 
     // audio bits
     audio_buffer: Vec<i16>,
@@ -46,8 +47,9 @@ struct MyEmulator {
 }
 
 impl MyEmulator {
-    pub fn with_core(core: impl AsRef<Path>) -> Pin<Box<Self>> {
-        let lib = libloading::Library::new(core.as_ref()).unwrap();
+    pub fn new(core_path: impl AsRef<Path>, sys_path: &Option<impl AsRef<Path>>) -> Pin<Box<Self>> {
+        let core_path = PathBuf::from(core_path.as_ref());
+        let lib = libloading::Library::new(&core_path).unwrap();
         let raw_retro = retro::loading::LibretroApi::from_library(lib).unwrap();
         let retro = retro::wrapper::LibretroWrapper::from(raw_retro);
 
@@ -72,18 +74,15 @@ impl MyEmulator {
 
         let sdl_context = sdl2::init().unwrap();
 
-        let (width, height) = (av_info.geometry.base_width, av_info.geometry.base_height);
-
         let window = sdl_context
             .video()
             .unwrap()
-            .window(title.as_str(), width, height)
+            .window(title.as_str(), av_info.geometry.base_width, av_info.geometry.base_height)
             .opengl()
             .build()
             .unwrap();
 
         let canvas = window.into_canvas().build().unwrap();
-        let texture_creator = canvas.texture_creator();
 
         let (audio_sender, audio_receiver) = crossbeam_channel::bounded(2);
 
@@ -115,18 +114,19 @@ impl MyEmulator {
 
         let emu = MyEmulator {
             retro,
+            core_path,
             av_info,
             sys_info,
             sdl_context,
             canvas,
             pixel_format,
-            texture_creator,
             audio_buffer: Default::default(),
             audio_spec: audio_spec.unwrap(),
             audio_device,
             audio_sender,
             gamepad_subsys,
             gamepads,
+            sys_path: sys_path.as_ref().map(|p| p.as_ref().to_path_buf())
         };
         let mut pin_emu = Box::pin(emu);
         retro::wrapper::set_handler(pin_emu.as_mut());
@@ -198,7 +198,8 @@ impl retro::wrapper::Handler for MyEmulator {
         let rect = Rect::new(0, 0, width, height);
 
         if let Ok(mut tex) =
-            self.texture_creator
+            self.canvas
+                .texture_creator()
                 .create_texture_static(self.pixel_format, width, height)
         {
             if tex.update(rect, data, pitch as usize).is_ok() {
@@ -248,6 +249,10 @@ impl retro::wrapper::Handler for MyEmulator {
 
     fn get_can_dupe(&mut self) -> Option<bool> { Some(true) }
 
+    fn get_system_directory(&mut self) -> Option<PathBuf> {
+        self.sys_path.clone()
+    }
+
     fn set_pixel_format(&mut self, pix_fmt: retro::ffi::PixelFormat) -> bool {
         self.pixel_format = match pix_fmt {
             retro::ffi::PixelFormat::ARGB1555 => sdl2::pixels::PixelFormatEnum::RGB555,
@@ -257,18 +262,22 @@ impl retro::wrapper::Handler for MyEmulator {
         true
     }
 
+    fn get_libretro_path(&mut self) -> Option<PathBuf> {
+        Some(self.core_path.clone())
+    }
+
+    fn get_save_directory(&mut self) -> Option<PathBuf> {
+        Some(std::env::temp_dir())
+    }
+
     fn set_system_av_info(&mut self, av_info: SystemAvInfo) -> bool {
-        let (width, height) = (av_info.geometry.base_width, av_info.geometry.base_height);
-        let _ = self.canvas.window_mut().set_size(width, height);
-        let _ = self.canvas.set_logical_size(width, height);
+        self.set_geometry(av_info.geometry.clone());
         self.av_info = av_info;
         true
     }
-
     fn set_geometry(&mut self, geom: GameGeometry) -> bool {
-        let (width, height) = (geom.base_width, geom.base_height);
-        let _ = self.canvas.window_mut().set_size(width, height);
-        let _ = self.canvas.set_logical_size(width, height);
+        let _ = self.canvas.window_mut().set_size(geom.base_width, geom.base_height);
+        let _ = self.canvas.set_logical_size(geom.base_width, geom.base_height);
         self.av_info.geometry = geom;
         true
     }
@@ -278,7 +287,6 @@ impl retro::wrapper::Handler for MyEmulator {
     }
 }
 
-
 struct MySdlAudio {
     audio_spec: AudioSpec,
     audio_receiver: crossbeam_channel::Receiver<Vec<i16>>,
@@ -298,7 +306,7 @@ impl AudioCallback for MySdlAudio {
 
 pub fn main() -> failure::Fallible<()> {
     let opt: Opt = Opt::from_args();
-    let mut emu = MyEmulator::with_core(&opt.core);
+    let mut emu = MyEmulator::new(&opt.core, &opt.system);
     emu.load_game(&opt.rom);
     emu.run();
 
@@ -310,9 +318,12 @@ struct Opt {
     /// Core module to use.
     #[structopt(short, long, parse(from_os_str))]
     core: PathBuf,
-    /// Rom to load using the core.
+    /// ROM to load using the core.
     #[structopt(short, long, parse(from_os_str))]
     rom: PathBuf,
+    /// System directory, often containing BIOS files
+    #[structopt(short, long, parse(from_os_str))]
+    system: Option<PathBuf>,
 }
 
 fn button_map(retro_button: &JoypadButton) -> Option<Button> {
diff --git a/src/retro/constants.rs b/src/retro/constants.rs
index 25d7bb1..39657ee 100644
--- a/src/retro/constants.rs
+++ b/src/retro/constants.rs
@@ -138,15 +138,8 @@ pub enum EnvRotation {
     CounterClockwise270 = 3,
 }
 
-pub struct EnvVariable {
-    key: &'static str,
-    description: &'static str,
-    expected_values: Vec<&'static str>,
-    value: Option<String>,
-}
-
 // TODO: experimental calls
-#[derive(TryFromPrimitive, IntoPrimitive)]
+#[derive(TryFromPrimitive, IntoPrimitive, Debug)]
 #[repr(u32)]
 pub enum EnvCmd {
     SetRotation = ENVIRONMENT_SET_ROTATION,
diff --git a/src/retro/wrapper.rs b/src/retro/wrapper.rs
index 4892db7..b077285 100644
--- a/src/retro/wrapper.rs
+++ b/src/retro/wrapper.rs
@@ -13,23 +13,20 @@ use num_enum::TryFromPrimitive;
 use super::constants::*;
 use super::ffi::*;
 use super::loading::*;
+use std::time::Duration;
 
 static mut CB_SINGLETON: StaticCallbacks = StaticCallbacks {
     handler: None,
 };
 
+// stable Rust doesn't have varargs, so we can't represent a callback with the signature of
+//  void (*retro_log_printf_t)(enum retro_log_level level, const char* fmt, ...)
+//  without a little help from an Actual-C wrapper.
 pub type WrappedLogPrintFn = extern "C" fn(level: LogLevel, fmt: *const c_char);
 extern "C"  {
     fn c_ext_handle_get_log_interface(cb: *mut LogCallback) -> bool;
     fn c_ext_set_log_print_cb(cb: WrappedLogPrintFn);
 }
-extern "C" fn rust_retro_ffi_log_print(level: LogLevel, msg: *const c_char) {
-    unsafe {
-        if let Some(cb) = CB_SINGLETON.handler.as_mut() {
-            cb.log_print(level, CStr::from_ptr(msg).to_string_lossy().as_ref());
-        }
-    }
-}
 
 #[allow(unused)]
 pub trait Handler: Unpin + 'static {
@@ -52,17 +49,12 @@ pub trait Handler: Unpin + 'static {
     fn get_system_directory(&mut self) -> Option<PathBuf> { None }
     fn set_pixel_format(&mut self, format: PixelFormat) -> bool { false }
     fn set_input_descriptors(&mut self, input_descriptors: &[InputDescriptor]) -> bool { false }
-    fn set_keyboard_callback(&mut self, cb: KeyboardCallback) -> bool { false }
-    fn set_disk_control_interface(&mut self, cb: DiskControlCallback) -> bool { false }
     fn set_hw_render(&mut self, hw_render_callback: HwRenderCallback) -> bool { false }
     fn get_variable(&mut self) -> Option<EnvVariable> { None }
     fn set_variables(&mut self, variables: &[EnvVariable]) -> bool { false }
     fn get_variable_update(&mut self) -> Option<bool> { None }
     fn set_support_no_game(&mut self, supports_no_game: bool) -> bool { false }
     fn get_libretro_path(&mut self) -> Option<PathBuf> { None }
-    fn set_frame_time_callback(&mut self, cb: FrameTimeCallback) -> bool { false }
-    fn set_audio_callback(&mut self, audio_callback: AudioCallback) -> bool { false }
-    fn get_rumble_interface(&mut self) -> Option<RumbleInterface> { None }
     fn get_input_device_capabilities(&mut self) -> Option<u64> { None }
     fn get_sensor_interface(&mut self) -> Option<SensorInterface> { None }
     fn get_camera_interface(&mut self) -> Option<CameraCallback> { None }
@@ -83,6 +75,7 @@ pub trait Handler: Unpin + 'static {
 
     // -- environment-set callbacks (API extensions) --
     fn log_print(&mut self, level: LogLevel, msg: &str) {}
+    fn set_rumble_state(&mut self, port: c_uint, effect: RumbleEffect, strength: u16) -> bool { false }
 }
 
 #[derive(Default)]
@@ -129,14 +122,24 @@ impl StaticCallbacks {
             // TODO EnvCmd::SetKeyboardCallback => {},
             // TODO EnvCmd::SetDiskControlInterface => {},
             // TODO EnvCmd::SetHwRender => {},
-            // TODO EnvCmd::GetVariable => {}, -- also change to mut parameter?
+            EnvCmd::GetVariable => {
+                // TODO: actually implement
+                let v = Self::from_void::<Variable>(data)?;
+                eprintln!(
+                    "Unsupported env cmd: GetVariable ({})",
+                    unsafe { CStr::from_ptr(v.key) }.to_string_lossy());
+                false
+            },
             // TODO EnvCmd::SetVariables => {},
             EnvCmd::GetVariableUpdate => Self::clone_into_void(data, &handler.get_variable_update()?)?,
             EnvCmd::SetSupportNoGame => handler.set_support_no_game(*Self::from_void(data)?),
             EnvCmd::GetLibretroPath => Self::path_into_void(data, handler.get_libretro_path()?)?,
             // TODO EnvCmd::SetFrameTimeCallback => {},
             // TODO EnvCmd::SetAudioCallback => {},
-            // TODO EnvCmd::GetRumbleInterface => {},
+            EnvCmd::GetRumbleInterface => {
+                let ri = RumbleInterface { set_rumble_state: StaticCallbacks::set_rumble_state_cb };
+                Self::clone_into_void(data, &ri)?
+            },
             EnvCmd::GetInputDeviceCapabilities => Self::clone_into_void(data, &handler.get_input_device_capabilities()?)?,
             // TODO EnvCmd::GetSensorInterface => {},
             // TODO EnvCmd::GetCameraInterface => {},
@@ -154,7 +157,10 @@ impl StaticCallbacks {
             EnvCmd::GetUsername => Self::string_into_void(data, handler.get_username()?)?,
             EnvCmd::GetLanguage => Self::clone_into_void(data, &handler.get_language()?)?,
             // EnvCmd::SetSerializationQuirks => handler.set_serialization_quirks(Self::from_void(data)?),
-            _ => false,
+            x => {
+                eprintln!("Unsupported env cmd: {:?}", x);
+                false
+            },
         }.into()
     }
     extern "C" fn environment_cb(cmd: u32, data: *mut c_void) -> bool {
@@ -167,7 +173,7 @@ impl StaticCallbacks {
         height: c_uint,
         pitch: usize,
     ) {
-        if !data.is_null() {
+        if !data.is_null() && data != HW_FRAME_BUFFER_VALID {
             if let Some(cb) = unsafe { CB_SINGLETON.handler.as_mut() } {
                 let data = data as *const u8;
                 let len = pitch * (height as usize);
@@ -208,10 +214,29 @@ impl StaticCallbacks {
             None => 0,
         }
     }
+
+    extern "C" fn log_print_cb(level: LogLevel, msg: *const c_char) {
+        unsafe {
+            if let Some(cb) = CB_SINGLETON.handler.as_mut() {
+                cb.log_print(level, CStr::from_ptr(msg).to_string_lossy().as_ref());
+            }
+        }
+    }
+
+    extern "C" fn set_rumble_state_cb(port: c_uint, effect: RumbleEffect, strength: u16) -> bool {
+        match unsafe { CB_SINGLETON.handler.as_mut() } {
+            Some(cb) => cb.set_rumble_state(port, effect, strength),
+            None => false,
+        }
+    }
 }
 
 pub struct LibretroWrapper {
     api: LibretroApi,
+    keyboard_event_cb: Option<KeyboardEventFn>,
+    frame_time_cb: Option<FrameTimeCallbackFn>,
+    audio_ready_cb: Option<AudioCallbackFn>,
+    audio_set_state_cb: Option<AudioSetStateCallbackFn>,
 }
 
 impl From<LibretroApi> for LibretroWrapper {
@@ -222,8 +247,30 @@ impl From<LibretroApi> for LibretroWrapper {
         api.set_audio_sample_batch(StaticCallbacks::audio_sample_batch_cb);
         api.set_input_poll(StaticCallbacks::input_poll_cb);
         api.set_input_state(StaticCallbacks::input_state_cb);
-        unsafe { c_ext_set_log_print_cb(rust_retro_ffi_log_print); }
-        LibretroWrapper { api }
+        unsafe { c_ext_set_log_print_cb(StaticCallbacks::log_print_cb); }
+        LibretroWrapper {
+            api,
+            keyboard_event_cb: None,
+            frame_time_cb: None,
+            audio_ready_cb: None,
+            audio_set_state_cb: None
+        }
+    }
+}
+
+impl LibretroWrapper {
+    // TODO: enum for the RETROK_* constants instead of c_uint for keycode...
+    pub fn keyboard_event(&self, down: bool, keycode: c_uint, character: u32, key_modifiers: u16) {
+        self.keyboard_event_cb.map(|f| unsafe { f(down, keycode, character, key_modifiers) });
+    }
+    pub fn frame_time(&self, time: Duration) {
+        self.frame_time_cb.map(|f| unsafe { f(time.as_micros() as Usec) });
+    }
+    pub fn audio_ready(&self) {
+        self.audio_ready_cb.map(|f| unsafe { f() });
+    }
+    pub fn audio_set_state(&self, enabled: bool) {
+        self.audio_set_state_cb.map(|f| unsafe { f(enabled) });
     }
 }