diff --git a/encoder/src/dec.rs b/encoder/src/dec.rs
index 3e73c27..cca9602 100644
--- a/encoder/src/dec.rs
+++ b/encoder/src/dec.rs
@@ -1,5 +1,45 @@
 use crate::*;
 
+pub fn cell_diff_8_horizontal(prev_frame: &Frame, encoded: &[u8], reader: &mut usize) -> Frame {
+	let bitmap = {
+		*reader += 3;
+		let mut bitmap = (encoded[0] as u32) << 16;
+		bitmap |= (encoded[1] as u32) << 8;
+		bitmap | encoded[2] as u32
+	};
+	let encoded = &encoded[3..];
+
+	let mut frame = *prev_frame;
+	let changed_pixel_count = bitmap.count_ones() as usize * 8 * 8;
+	let (runs, new_pixels) = rle_255_decode_until(encoded, changed_pixel_count);
+	*reader += runs;
+
+	let cells_x = WIDTH / 8;
+	let cells_y = HEIGHT / 8;
+	let mut index = 0;
+
+	for celly in 0..cells_y {
+		for cellx in 0..cells_x {
+			let is_changed = (bitmap >> (cellx + cells_x * celly)) & 1;
+			if is_changed == 1 {
+				let pixels = &new_pixels[(index * 8 * 8)..((index + 1) * 8 * 8)];
+				let mut i = 0;
+				for dx in 0..8 {
+					for dy in 0..8 {
+						let x = cellx * 8 + dx;
+						let y = celly * 8 + dy;
+						frame[x][y] = pixels[i];
+						i += 1;
+					}
+				}
+				index += 1;
+			}
+		}
+	}
+
+	frame
+}
+
 pub fn bg_strips_horizontal(_prev_frame: &Frame, encoded: &[u8], reader: &mut usize) -> Frame {
 	*reader += 1;
 	let bg = encoded[0] >> 7;
diff --git a/encoder/src/enc.rs b/encoder/src/enc.rs
index e7e0f92..2c29754 100644
--- a/encoder/src/enc.rs
+++ b/encoder/src/enc.rs
@@ -1,5 +1,43 @@
 use crate::*;
 
+pub fn cell_diff_8_horizontal(prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
+	let cells_x = WIDTH / 8;
+	let cells_y = HEIGHT / 8;
+	let loss = 0;
+
+	let mut bitmap: u32 = 0;
+	let mut changed_pixels = Vec::new();
+
+	for celly in 0..cells_y {
+		for cellx in 0..cells_x {
+			let mut changed = 0;
+			let mut cell_contents = Vec::new();
+			// todo try encoding the cells in frame space instead of one cell at a time
+			for dx in 0..8 {
+				for dy in 0..8 {
+					let x = cellx * 8 + dx;
+					let y = celly * 8 + dy;
+					let pixel = frame[x][y];
+					cell_contents.push(pixel);
+					if pixel != prev_frame[x][y] {
+						changed += 1;
+					}
+				}
+			}
+			if changed > loss {
+				bitmap |= 1 << (cellx + cells_x * celly);
+				changed_pixels.extend_from_slice(&cell_contents);
+			}
+		}
+	}
+	let mut data = vec![(bitmap >> 16) as u8, (bitmap >> 8) as u8, bitmap as u8];
+	data.extend_from_slice(&rle_255_encode(&changed_pixels));
+	EncodedFrame {
+		encoding: Encoding::CellDiff8H,
+		data,
+	}
+}
+
 pub fn bg_strips_horizontal(_prev_frame: &Frame, frame: &Frame) -> EncodedFrame {
 	let bg = most_common_pixel(frame);
 	fn pack_strip(x: usize, y: usize, width: usize) -> [u8; 2] {
diff --git a/encoder/src/main.rs b/encoder/src/main.rs
index daadb9c..60e9e52 100644
--- a/encoder/src/main.rs
+++ b/encoder/src/main.rs
@@ -8,6 +8,7 @@ pub use util::*;
 
 const INSPECT_ENC: bool = false;
 const INSPECT_DEC: bool = false;
+const MAX_ERROR: usize = 0;
 
 fn main() {
 	let frames = get_all_frames("../video/frames/");
@@ -56,8 +57,8 @@ fn encode(frames: &[Frame]) -> Vec<u8> {
 		enc::rle_diff_horizontal,
 		enc::rle_diff_vertical,
 		enc::bg_strips_horizontal,
+		enc::cell_diff_8_horizontal,
 	];
-	let max_error = 0;
 
 	let mut last_frame = FRAME_0;
 	for (i, frame) in frames.iter().enumerate() {
@@ -67,7 +68,7 @@ fn encode(frames: &[Frame]) -> Vec<u8> {
 			let decode = get_matching_decoder(encoded.encoding);
 			let decoded = decode(&last_frame, &encoded.data, &mut 0);
 			let error = frame_error(frame, &decoded);
-			if error <= max_error {
+			if error <= MAX_ERROR {
 				options.push(encoded);
 			} else {
 				// dbg!(&encoded);
@@ -108,7 +109,7 @@ enum Encoding {
 	// BGStripsV,
 	// QuadTree,
 	// DrawCommands,
-	// CellDiff8H,
+	CellDiff8H,
 	// CellDiff8V,
 	// CellDiff4HH,
 	// CellDiff4HV,
@@ -128,7 +129,7 @@ fn get_matching_decoder(encoding: Encoding) -> FrameDecoder {
 		// Encoding::BGStripsV => todo!(),
 		// Encoding::QuadTree => todo!(),
 		// Encoding::DrawCommands => todo!(),
-		// Encoding::CellDiff8H => todo!(),
+		Encoding::CellDiff8H => dec::cell_diff_8_horizontal,
 		// Encoding::CellDiff8V => todo!(),
 		// Encoding::CellDiff4HH => todo!(),
 		// Encoding::CellDiff4HV => todo!(),