diff --git a/Cargo.toml b/Cargo.toml
index 7bfa3f1..8491fda 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "fimg"
-version = "0.4.10"
+version = "0.4.11"
 authors = ["bend-n <bend.n@outlook.com>"]
 license = "MIT"
 edition = "2021"
diff --git a/src/affine.rs b/src/affine.rs
index 893be81..f4c311e 100644
--- a/src/affine.rs
+++ b/src/affine.rs
@@ -188,9 +188,7 @@ unsafe fn transpose_non_power_of_two<const CHANNELS: usize, T: DerefMut<Target =
     for i in 0..size {
         for j in i..size {
             // SAFETY: caller ensures squarity
-            unsafe {
-                b.swap_unchecked(i * size + j, j * size + i);
-            };
+            unsafe { b.swap_unchecked(i * size + j, j * size + i) };
         }
     }
 }
diff --git a/src/drawing/circle.rs b/src/drawing/circle.rs
new file mode 100644
index 0000000..793dd92
--- /dev/null
+++ b/src/drawing/circle.rs
@@ -0,0 +1,67 @@
+//! draw 2d circles
+use crate::Image;
+use std::ops::DerefMut;
+
+impl<T: DerefMut<Target = [u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
+    /// Draws a circle, using the [Bresenham's circle](https://en.wikipedia.org/wiki/Midpoint_circle_algorithm) algorithm.
+    /// ```
+    /// # use fimg::Image;
+    /// let mut i = Image::alloc(50, 50);
+    /// i.border_circle((25, 25), 20, [255]);
+    /// # assert_eq!(i.buffer(), include_bytes!("../../tdata/circle.imgbuf"));
+    /// ```
+    pub fn border_circle(&mut self, (xc, yc): (i32, i32), radius: i32, c: [u8; CHANNELS]) {
+        let mut x = 0;
+        let mut y = radius;
+        let mut p = 1 - radius;
+        /// bounds the pixels
+        macro_rules! bound {
+            ($($x:expr,$y:expr);+;) => {
+                $(if $x >= 0 && $x < self.width() as i32 && $y >= 0 && $y < self.height() as i32 {
+                    // SAFETY: ^
+                    unsafe { self.set_pixel($x as u32, $y as u32, c) };
+                })+
+            };
+        }
+        while x <= y {
+            bound! {
+                xc + x, yc + y;
+                xc + y, yc + x;
+                xc - y, yc + x;
+                xc - x, yc + y;
+                xc - x, yc - y;
+                xc - y, yc - x;
+                xc + y, yc - x;
+                xc + x, yc - y;
+            };
+            x += 1;
+            if p < 0 {
+                p += 2 * x + 1;
+            } else {
+                y -= 1;
+                p += 2 * (x - y) + 1;
+            }
+        }
+    }
+
+    /// Draw a filled circle.
+    /// ```
+    /// # use fimg::Image;
+    /// let mut i = Image::alloc(50, 50);
+    /// i.circle((25, 25), 20, [255]);
+    /// # assert_eq!(i.buffer(), include_bytes!("../../tdata/circle2.imgbuf"));
+    /// ```
+    pub fn circle(&mut self, (xc, yc): (i32, i32), radius: i32, c: [u8; CHANNELS]) {
+        for x in -radius..radius {
+            let h = ((radius * radius - x * x) as f32).sqrt().round() as i32;
+            for y in -h..h {
+                let x = x + xc;
+                let y = y + yc;
+                if x >= 0 && x < self.width() as i32 && y >= 0 && y < self.height() as i32 {
+                    // SAFETY: ^
+                    unsafe { self.set_pixel(x as u32, y as u32, c) };
+                }
+            }
+        }
+    }
+}
diff --git a/src/drawing/mod.rs b/src/drawing/mod.rs
index 87b4b88..ebc4e99 100644
--- a/src/drawing/mod.rs
+++ b/src/drawing/mod.rs
@@ -1,5 +1,6 @@
-//! contains drawing operations, like {line, box, triangle, polygon} drawing
+//! contains drawing operations, like {line, box, triangle, polygon, circle} drawing
 mod r#box;
+mod circle;
 mod line;
 mod poly;
 mod tri;
diff --git a/src/drawing/poly.rs b/src/drawing/poly.rs
index e0dd017..3847a56 100644
--- a/src/drawing/poly.rs
+++ b/src/drawing/poly.rs
@@ -86,6 +86,7 @@ impl<T: DerefMut<Target = [u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
     }
 
     /// Draws a regular convex polygon with a specified number of sides, a radius, and a rotation (radians).
+    /// Prefer [`Image::circle`] over `poly(.., 600, ..)`.
     /// Calls into [`Image::tri`] and [`Image::quad`].
     /// ```
     /// # use fimg::Image;
@@ -113,7 +114,7 @@ impl<T: DerefMut<Target = [u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
                 self.tri(
                     add(trans(space + rotation)),
                     add(trans(rotation)),
-                    add(trans(space * 2.0 + rotation)),
+                    add(trans(space.mul_add(2.0, rotation))),
                     c,
                 );
             }
@@ -122,9 +123,9 @@ impl<T: DerefMut<Target = [u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
                 for i in (0..sides - 1).step_by(2).map(|i| i as f32) {
                     self.quad(
                         r((x, y)),
-                        r(add(trans(space * i + rotation))),
-                        r(add(trans(space * (i + 1.) + rotation))),
-                        r(add(trans(space * (i + 2.) + rotation))),
+                        r(add(trans(space.mul_add(i, rotation)))),
+                        r(add(trans(space.mul_add(i + 1., rotation)))),
+                        r(add(trans(space.mul_add(i + 2., rotation)))),
                         c,
                     );
                 }
@@ -134,8 +135,8 @@ impl<T: DerefMut<Target = [u8]>, const CHANNELS: usize> Image<T, CHANNELS> {
                     // the missing piece
                     self.tri(
                         (x, y),
-                        add(trans(space * i + rotation)),
-                        add(trans(space * (i + 1.) + rotation)),
+                        add(trans(space.mul_add(i, rotation))),
+                        add(trans(space.mul_add(i + 1., rotation))),
                         c,
                     );
                 }
diff --git a/tdata/circle.imgbuf b/tdata/circle.imgbuf
new file mode 100644
index 0000000..3235779
Binary files /dev/null and b/tdata/circle.imgbuf differ
diff --git a/tdata/circle2.imgbuf b/tdata/circle2.imgbuf
new file mode 100644
index 0000000..26d22fd
Binary files /dev/null and b/tdata/circle2.imgbuf differ