diff --git a/README.md b/README.md
index 5d26841..91f3a80 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,5 @@
 # marble "programming language"
-Source code is ascii art that describes a marble track. Marbles carry one byte of data each and move around interacting with parts of the board. Marbles can be created and destroyed arbitrarily by the various operators.
+Marbles carry one unsigned 32 bit integer each and move around interacting with tiles on the board. Source code is ascii art that describes a marble machine. Marbles can be created and destroyed arbitrarily by the various operators.
 
 ## physics
 Marbles (`o`) start out moving down (unless emitted by something).
@@ -25,7 +25,7 @@ P P
 - `B` Bag: consumes marbles that move into it, and emits an empty (0) marble when powered.
 - `ASMDR` Math: Add/Subtract/Multiply/Divide/Remainder of the marble on the left and the right, relative to the power direction. Outputs a marble forward if at least one input exists.
 - `LG=!` Logic gates: (Less/Greater/Equal/Not Equal) compares the left and right input (both treated as 0 if absent) when powered, and powers forward if the result is true.
-- `P` Print: Prints the value of the front marble when powered
+- `P` Print: Prints the value of the front marble when powered, truncated to a single byte.
 - `I` Input: Outputs a marble with the next byte from the program input stream, if there are any
 - `0123456789` Digits: decimal digits are added to a marbles value after multiplying the marble with 10, this means that a marble passing over `123` would contain the number 123 afterwards. Digits are consumed by marbles passing over them.
 
diff --git a/programs/adder.mbl b/programs/adder.mbl
index d01f5c4..4657b31 100644
--- a/programs/adder.mbl
+++ b/programs/adder.mbl
@@ -1,9 +1,9 @@
 (print sum of 123 and 45)
 
   o
-  > 123   B
+  > 1230  B
  vo      A-+
-  > 45    B|
+  > 45898 B|
   o      --+
   >      *  B
          o
diff --git a/src/main.rs b/src/main.rs
index 7514e56..3a633e9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,8 @@ use owo_colors::OwoColorize;
 mod grid;
 use grid::*;
 
+type MarbleValue = u32;
+
 #[derive(Debug)]
 struct Machine {
 	grid: Grid<Tile>,
@@ -24,7 +26,7 @@ enum Tile {
 	Comment(u8),
 	Bag,
 	Marble {
-		value: u8,
+		value: MarbleValue,
 		dir: Direction,
 	},
 	Trigger,
@@ -230,12 +232,16 @@ impl Machine {
 			}
 			print!(" :: ");
 			for (val, dir) in marbles_on_row {
-				print!("{}", format!("{}{:<3} ", dir.char(), val).magenta())
+				print!("{}", format!("{}{} ", dir.char(), val).magenta())
 			}
 			println!();
 		}
-		println!("output: {}", String::from_utf8_lossy(&self.output));
-		println!("input: {}", String::from_utf8_lossy(&self.input));
+		if !self.output.is_empty() {
+			println!("output: '{}'", String::from_utf8_lossy(&self.output));
+		}
+		if !self.input.is_empty() {
+			println!("input: '{}'", String::from_utf8_lossy(&self.input));
+		}
 		println!("steps: {}", self.steps);
 	}
 
@@ -271,7 +277,9 @@ impl Machine {
 						new_tile = Some(Tile::Blank);
 					}
 					Tile::Digit(d) => {
-						let new_val = value.wrapping_mul(10).wrapping_add(*d - b'0');
+						let new_val = value
+							.wrapping_mul(10)
+							.wrapping_add((*d - b'0') as MarbleValue);
 						*target = Tile::Marble {
 							value: new_val,
 							dir,
@@ -378,7 +386,7 @@ impl Machine {
 			Tile::Print => {
 				let sample = self.grid.get(front_pos);
 				if let Tile::Marble { value, dir: _ } = sample {
-					self.output.push(value);
+					self.output.push(value as u8);
 				}
 			}
 			Tile::Bag => {
@@ -389,7 +397,7 @@ impl Machine {
 			}
 			Tile::Input => {
 				if self.input_index < self.input.len() && self.grid.get(front_pos).is_blank() {
-					let value = self.input[self.input_index];
+					let value = self.input[self.input_index] as MarbleValue;
 					*self.grid.get_mut(front_pos) = Tile::Marble { value, dir };
 					self.marbles.push(front_pos);
 					self.input_index += 1;
@@ -467,7 +475,7 @@ impl Machine {
 }
 
 impl Tile {
-	fn read_value(&self) -> u8 {
+	fn read_value(&self) -> MarbleValue {
 		if let Tile::Marble { value, dir: _ } = self {
 			*value
 		} else {