implement level completion, score storing and a dismissable 'level complete' popup

src/marble_engine.rs

@@ -17,7 +17,7 @@ pub struct Machine {
 }
 
 impl Machine {
-	pub fn new_empty(input:Vec<u8>,width: usize) -> Self {
+	pub fn new_empty(input: Vec<u8>, width: usize) -> Self {
 		Self {
 			board: Board::new_empty(width, width),
 			marbles: Vec::new(),
@@ -58,6 +58,10 @@ impl Machine {
 		&self.input
 	}
 
+	pub fn step_count(&self) -> usize {
+		self.steps
+	}
+
 	pub fn set_input(&mut self, bytes: Vec<u8>) {
 		self.input_index = self.input_index.min(bytes.len());
 		self.input = bytes;