diff --git a/core/src/geom.rs b/core/src/geom.rs
index 426419b5..5ba5b6f4 100644
--- a/core/src/geom.rs
+++ b/core/src/geom.rs
@@ -13,3 +13,7 @@ pub struct Tri<V>(pub [V; 3]);
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 #[repr(transparent)]
 pub struct Plane<V>(pub(crate) V);
+
+pub fn vertex<P, A>(pos: P, attrib: A) -> Vertex<P, A> {
+    Vertex { pos, attrib }
+}
diff --git a/core/src/render.rs b/core/src/render.rs
index ed025373..dddc98d0 100644
--- a/core/src/render.rs
+++ b/core/src/render.rs
@@ -18,7 +18,6 @@ use crate::math::mat::{RealToProjective, RealToReal};
 use crate::math::{Linear, Mat4x4, Vec3};
 
 pub mod clip;
-pub mod ctx;
 pub mod raster;
 pub mod shader;
 pub mod target;
diff --git a/demos/Cargo.toml b/demos/Cargo.toml
index d18c661b..9f5aa7ce 100644
--- a/demos/Cargo.toml
+++ b/demos/Cargo.toml
@@ -1,9 +1,22 @@
 [package]
 name = "retrofire-demos"
-version = "0.1.0"
+version = "0.3.0"
 edition = "2021"
 license.workspace = true
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+re = { path = "../core", package="retrofire-core", features = ["std"] }
+rf = { path = "../front", package = "retrofire-front" }
+
+minifb = { version = "0.25.0", optional = true }
+softbuffer = { version = "0.3.0", optional = true }
+winit = { version = "0.28.6", optional = true }
+
+[features]
+minifb = ["dep:minifb", "rf/minifb"]
+
+[[bin]]
+name = "square"
+required-features = ["minifb"]
diff --git a/demos/src/bin/square.rs b/demos/src/bin/square.rs
new file mode 100644
index 00000000..19904bff
--- /dev/null
+++ b/demos/src/bin/square.rs
@@ -0,0 +1,58 @@
+#![cfg(feature = "minifb")]
+
+use std::ops::ControlFlow::Continue;
+
+use re::geom::{vertex, Tri, Vertex};
+use re::math::color::{rgb, Color3f};
+use re::math::mat::{perspective, rotate_z, translate, viewport};
+use re::math::{rads, vec2, vec3, Mat4x4, Vec3};
+use re::render::raster::Frag;
+use re::render::shader::Shader;
+use re::render::{render, ModelToProjective, ModelToView};
+use rf::minifb::Window;
+
+fn main() {
+    let verts = [
+        vertex(vec3(-1.0, -1.0, 0.0), rgb(1.0, 0.3, 0.1)),
+        vertex(vec3(-1.0, 1.0, 0.0), rgb(0.2, 0.8, 0.3)),
+        vertex(vec3(1.0, -1.0, 0.0), rgb(0.2, 0.5, 1.0)),
+        vertex(vec3(1.0, 1.0, 0.0), rgb(1.0, 0.3, 0.1)),
+    ];
+
+    let mut win = Window::builder()
+        .title("minifb front demo")
+        .size(640, 480)
+        .build();
+
+    let shader = Shader::new(
+        |Vertex { pos, attrib }: Vertex<Vec3, _>,
+         mvp: &Mat4x4<ModelToProjective>| {
+            vertex(mvp.apply(&pos.to()), attrib)
+        },
+        |frag: Frag<Color3f>| frag.var.to_color4(),
+    );
+
+    let modelview = translate(vec3(0.0, 0.0, 2.0));
+    let project = perspective(1.0, 4.0 / 3.0, 0.1..1000.0);
+    let viewport = viewport(vec2(10, 10)..vec2(630, 470));
+
+    win.run(|frame| {
+        let secs = frame.t.as_secs_f32();
+
+        let mv: Mat4x4<ModelToView> = modelview
+            .compose(&rotate_z(rads(secs)))
+            .compose(&translate(vec3(0.0, 0.0, secs.sin())))
+            .to();
+        let mvp = mv.then(&project);
+
+        render(
+            &[Tri([0, 1, 2]), Tri([3, 2, 1])],
+            &verts,
+            &shader,
+            &mvp,
+            viewport,
+            &mut frame.buf,
+        );
+        Continue(())
+    });
+}
diff --git a/front/src/lib.rs b/front/src/lib.rs
index da4bd66a..292e56a5 100644
--- a/front/src/lib.rs
+++ b/front/src/lib.rs
@@ -4,8 +4,11 @@ pub mod minifb;
 #[cfg(feature = "sdl2")]
 pub mod sdl2;
 
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn test() {}
+pub struct Frame<'a> {
+    // Time since first frame.
+    pub t: Duration,
+    // Time since last frame.
+    pub dt: Duration,
+    // Framebuffer in which to draw.
+    pub buf: Framebuf<MutSlice2<'a, u32>, MutSlice2<'a, f32>>,
 }
diff --git a/front/src/minifb.rs b/front/src/minifb.rs
index e69de29b..d39086ed 100644
--- a/front/src/minifb.rs
+++ b/front/src/minifb.rs
@@ -0,0 +1,132 @@
+//! Frontend using the `minifb` crate for window creation and event handling.
+
+use std::ops::ControlFlow::{self, Break};
+use std::time::{Duration, Instant};
+
+use minifb::{Key, KeyRepeat, WindowOptions};
+
+use retrofire_core::render::target::Framebuf;
+use retrofire_core::util::buf::{AsMutSlice2, Buf2};
+
+use crate::Frame;
+
+pub struct Window {
+    /// The wrapped minifb window.
+    pub imp: minifb::Window,
+    /// The width and height of the window.
+    pub size: (usize, usize),
+}
+
+/// Builder for creating `Window`s.
+pub struct Builder<'title> {
+    pub size: (usize, usize),
+    pub title: &'title str,
+    pub max_fps: Option<f32>,
+    pub opts: WindowOptions,
+}
+
+impl Default for Builder<'_> {
+    fn default() -> Self {
+        Self {
+            size: (800, 600),
+            title: "// retrofire application //",
+            max_fps: Some(60.0),
+            opts: WindowOptions::default(),
+        }
+    }
+}
+
+impl<'t> Builder<'t> {
+    /// Sets the width and height of the window.
+    pub fn size(mut self, w: usize, h: usize) -> Self {
+        self.size = (w, h);
+        self
+    }
+    /// Sets the title of the window.
+    pub fn title(mut self, title: &'t str) -> Self {
+        self.title = title;
+        self
+    }
+    /// Sets the fps cap of the window.
+    pub fn max_fps(mut self, fps: Option<f32>) -> Self {
+        self.max_fps = fps;
+        self
+    }
+    /// Sets other `minifb` options.
+    pub fn options(mut self, opts: WindowOptions) -> Self {
+        self.opts = opts;
+        self
+    }
+
+    /// Creates the window.
+    pub fn build(self) -> Window {
+        let mut imp = minifb::Window::new(
+            self.title,
+            self.size.0,
+            self.size.1,
+            self.opts,
+        )
+        .unwrap();
+        imp.limit_update_rate(
+            self.max_fps
+                .map(|fps| Duration::from_secs_f32(1.0 / fps)),
+        );
+        Window {
+            imp,
+            size: self.size,
+        }
+    }
+}
+
+impl Window {
+    /// Returns a window builder.
+    pub fn builder() -> Builder<'static> {
+        Builder::default()
+    }
+
+    /// Updates the window content with `fb`.
+    /// # Panics
+    pub fn present(&mut self, fb: &[u32]) {
+        let (w, h) = self.size;
+        self.imp.update_with_buffer(fb, w, h).unwrap();
+    }
+
+    /// Repeatedly calls `frame_fn`
+    pub fn run<F>(&mut self, mut frame_fn: F)
+    where
+        F: FnMut(&mut Frame) -> ControlFlow<()>,
+    {
+        let (w, h) = self.size;
+        let mut cb = Buf2::new_default(w, h);
+        let mut zb = Buf2::new_default(w, h);
+
+        let start = Instant::now();
+        let mut last = Instant::now();
+        loop {
+            if !self.imp.is_open()
+                || self
+                    .imp
+                    .is_key_pressed(Key::Escape, KeyRepeat::No)
+            {
+                return;
+            }
+
+            cb.fill(0);
+            zb.fill(f32::INFINITY);
+
+            let frame = &mut Frame {
+                t: start.elapsed(),
+                dt: last.elapsed(),
+                buf: Framebuf {
+                    color_buf: cb.as_mut_slice2(),
+                    depth_buf: zb.as_mut_slice2(),
+                },
+            };
+            last = Instant::now();
+            if let Break(()) = frame_fn(frame) {
+                return;
+            }
+            self.present(cb.data_mut());
+        }
+    }
+}