diff --git a/src/main.rs b/src/main.rs
index 5acbd1e..ee52349 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,16 +1,33 @@
 use std::fmt;
-//use std::collections::HashSet;
+use std::collections::HashSet;
 use rand::seq::SliceRandom;
+use std::time::Instant;
+use std::env;
+use std::process;
+use text_io::read;
+use std::cmp::min;
+
+enum LineType {
+	Top,
+	Middle,
+	Bottom,
+}
+
+enum DisplayMode {
+	Full,
+	Focus(usize),
+}
 
 #[derive(Clone)]
 struct Cell {
-	value: Option<u8>,
-	possibilities: Vec<u8>
+	value: Option<usize>,
+	max: usize,
+	possibilities: Vec<usize>
 }
 
 impl Cell {
-	fn set(&mut self, value: u8) {
-		self.value = if value > 0 && value < 10 {
+	fn set(&mut self, value: usize) {
+		self.value = if value > 0 && value <= self.max {
 			Some(value)
 		} else {
 			None
@@ -18,108 +35,140 @@ impl Cell {
 	}
 
 	fn reset_possibilities(&mut self) {
-		self.possibilities = (1..=9).collect();
+		self.possibilities = (1..=self.max).collect();
 	}
 
-	fn remove_possibilities(&mut self, possibilities: &Vec<u8>) {
+	fn remove_possibilities(&mut self, possibilities: &HashSet<usize>) {
 		self.possibilities.retain(|&x| !possibilities.contains(&x))
 	}
-}
 
-impl Default for Cell {
-	fn default() -> Self {
+	fn new(max: usize) -> Self {
 		Self {
 			value: None,
-			possibilities: (1..=9).collect(),
+			max,
+			possibilities: (1..=max).collect(),
 		}
 	}
 }
 
 impl fmt::Display for Cell {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if let Some(v) = self.value {
-            write!(f, "{}", v)
+        if let Some(value) = self.value {
+			write!(f, "{}", to_base35(value))
         } else {
-            write!(f, " ")
+        	write!(f, " ")
         }
     }
 }
 
 struct Choice {
 	cell_selected: [usize; 2],
-	possibilities: Vec<u8>,
-	selected_value: u8,
+	possibilities: Vec<usize>,
+	selected_value: usize,
 }
 
 struct Sudoku {
-	grid: [[Cell; 9]; 9],
+	grid: Vec<Vec<Cell>>,
 	rng: rand::rngs::ThreadRng,
 	history: Vec<Choice>,
+	size: usize,
+	square_size: usize,
 }
 
 impl Sudoku {
-	fn new(sudoku_set: [[u8; 9]; 9]) -> Self {
-		let mut sudoku_grid: [[Cell; 9]; 9] = [[(); 9]; 9].map(|_| [(); 9].map(|_| Cell::default()));
-
-	    for (row_index, row) in sudoku_set.iter().enumerate(){
-        	for (column_index, value) in row.iter().enumerate() {
-        		sudoku_grid[row_index][column_index].set(*value)
-        	}
-        }
+	fn new(order: usize) -> Self {
+		let size = order*order;
+		let sudoku_grid: Vec<Vec<Cell>> = vec![vec![Cell::new(size); size]; size];
 
 		Self {
 			grid: sudoku_grid,
 			rng: rand::thread_rng(),
 			history: vec![],
+			size,
+			square_size: order,
 		}
 	}
 
-	fn display(&self) {
-		println!("# sudoku grid : ");
-        for row in &self.grid {
-        	let mut line: String = "[".to_string();
-        	for cell in row {
-        		line += &format!("{}|",cell);
+	fn display(&self, display_mode: DisplayMode) {
+		self.draw_line(LineType::Top);
+        for (row_index, row) in self.grid.iter().enumerate() {
+        	if row_index % self.square_size == 0 && row_index != 0 {
+        		self.draw_line(LineType::Middle);
         	}
-        	line.pop();
-        	println!("{}]",line);
+        	
+        	let mut line: String = "║ ".to_string();
+        	for (cell_index, cell) in row.iter().enumerate() {
+        	
+        		line += &format!("{} ",cell);
+
+        		if cell_index % self.square_size == self.square_size - 1 {
+					line+= "║ ";
+        		}
+        	}
+        	if let DisplayMode::Focus(focus_row) = display_mode {
+        		if row_index == focus_row {
+        			line += "<";
+        		}
+        	}
+        	println!("{}",line);
         }
+        
+   		self.draw_line(LineType::Bottom);
+    }
+
+    fn draw_line(&self, line_type: LineType) {
+    	let (left_corner, intersection, right_corner) = match line_type {
+    		LineType::Top => ("╔", "╦", "╗"),
+    		LineType::Middle => ("╠", "╬", "╣"),
+    		LineType::Bottom => ("╚", "╩", "╝"),
+    	};
+    	
+    	let mut line = left_corner.to_string();
+         for i in 0..(self.square_size) {
+         	line += &"═".repeat(self.square_size*2+1);
+         	if i < self.square_size - 1 {
+         		line += intersection;
+         	} 
+         }
+         println!("{}{}", line, right_corner);
     }
 
     fn update_possibilities(&mut self) {
-    	let mut row_used_values: [Vec<u8>;9] = [vec![],vec![],vec![],vec![],vec![],vec![],vec![],vec![],vec![]];
-    	let mut column_used_values: [Vec<u8>;9] = [vec![],vec![],vec![],vec![],vec![],vec![],vec![],vec![],vec![]];
-    	let mut square_used_values: [[Vec<u8>;3];3] = [[vec![],vec![],vec![]],[vec![],vec![],vec![]],[vec![],vec![],vec![]]];  
+    	let mut row_used_values: Vec<HashSet<usize>> = vec![HashSet::new(); self.size];
+    	let mut column_used_values: Vec<HashSet<usize>> = vec![HashSet::new(); self.size];
+    	let mut square_used_values: Vec<Vec<HashSet<usize>>> = vec![vec![HashSet::new(); self.square_size]; self.square_size];
     	
-		for row_index in 0..9 {
-			for column_index in 0..9 {
+		for row_index in 0..self.size {
+			for column_index in 0..self.size {
 				let Some(value) = self.grid[row_index][column_index].value else {
 					continue
 				};
-				row_used_values[row_index].push(value);
-				column_used_values[column_index].push(value);
-				square_used_values[row_index/3][column_index/3].push(value);
+				row_used_values[row_index].insert(value);
+				column_used_values[column_index].insert(value);
+				square_used_values[row_index/self.square_size][column_index/self.square_size].insert(value);
 			}
 		}
 		
-		for row_index in 0..9 {
-			for column_index in 0..9 {
-				self.grid[row_index][column_index].remove_possibilities(&row_used_values[row_index]);
-				self.grid[row_index][column_index].remove_possibilities(&column_used_values[column_index]);
-				self.grid[row_index][column_index].remove_possibilities(&square_used_values[row_index/3][column_index/3]);
+		for row_index in 0..self.size {
+			for column_index in 0..self.size {
+				let mut used_values = row_used_values[row_index].clone();
+	            used_values.extend(&column_used_values[column_index]);
+	            used_values.extend(&square_used_values[row_index/self.square_size][column_index/self.square_size]);
+	            
+				self.grid[row_index][column_index].remove_possibilities(&used_values);
 			}
 		}
     }
 
-    fn collapse(&mut self) -> bool {
+    fn collapse(&mut self, debug_display: bool) -> bool {
 		let mut min_row_index: usize = 0;
 		let mut min_column_index: usize = 0;
-		let mut min_len: usize = 9;
+		let mut min_len: usize = self.size;
 
 		let mut grid_has_empty_cell: bool = false;
 		
-    	for row_index in 0..9 {
-    		for column_index in 0..9 {
+    	for row_index in 0..self.size {
+    		for column_index in 0..self.size {
     			if !self.grid[row_index][column_index].value.is_none() {
     				continue;
     			}
@@ -134,18 +183,22 @@ impl Sudoku {
     	}
 
     	if !grid_has_empty_cell {
-    		println!("x no empty cells");
+    		if debug_display {
+    			println!("x no empty cells");
+    		}
     		return false
     	}
     	
-    	if self.collapse_cell(min_row_index, min_column_index) {
+    	if self.collapse_cell(min_row_index, min_column_index, debug_display) {
    	        return true
    	    }
 
 		let mut fork: Option<Choice> = None;
 		
         while let Some(choice) = self.history.pop() {
-        	println!("* backtracking");
+        	if debug_display {
+        		println!("* backtracking");
+        	}
         	self.grid[choice.cell_selected[0]][choice.cell_selected[1]].value = None;
         	if choice.possibilities.len() > 1 {
         		fork = Some(choice);
@@ -154,13 +207,19 @@ impl Sudoku {
         }
 
         let Some(choice) = fork else {
-        	println!("x backtracked to start");
+        	if debug_display {
+        		println!("x backtracked to start");
+        	}
         	return false
         };
         
        	self.reset_possibilities();
-		self.grid[choice.cell_selected[0]][choice.cell_selected[1]].remove_possibilities(&vec![choice.selected_value]);
-       	return self.collapse_cell(choice.cell_selected[0], choice.cell_selected[1])
+
+       	let mut selected_value = HashSet::new();
+       	selected_value.insert(choice.selected_value);
+       	
+		self.grid[choice.cell_selected[0]][choice.cell_selected[1]].remove_possibilities(&selected_value);
+       	return self.collapse_cell(choice.cell_selected[0], choice.cell_selected[1], debug_display)
     }
 
     fn reset_possibilities(&mut self) {
@@ -173,9 +232,11 @@ impl Sudoku {
         self.update_possibilities();
     }
 
-    fn collapse_cell(&mut self, row_index: usize, column_index: usize) -> bool {
+    fn collapse_cell(&mut self, row_index: usize, column_index: usize, debug_display: bool) -> bool {
     	let Some(&selected_value) = self.grid[row_index][column_index].possibilities.choose(&mut self.rng) else {
-   	    	println!("x no possibilities for [{}][{}]", row_index, column_index);
+			if debug_display {
+   	    		println!("x no possibilities for [{}][{}]", row_index, column_index);
+   	    	}
 			return false
 		};
 
@@ -186,60 +247,93 @@ impl Sudoku {
 		});
 
   	    self.grid[row_index][column_index].set(selected_value);
-		println!("# collapsing [{}][{}] ({:?}) to {}", row_index, column_index, self.grid[row_index][column_index].possibilities, selected_value);
+  	    if debug_display {
+			println!("# collapsing [{}][{}] ({:?}) to {}", row_index, column_index, self.grid[row_index][column_index].possibilities, selected_value);
+		}
 		return true
 	}
 
-	fn solve(&mut self, display: bool) {
-		if display {
-		    self.display();
-			println!("--------");
-		}
+	fn solve(&mut self, debug_display: bool) {
+		let now = Instant::now();
+		
+		self.display(DisplayMode::Full);
+		if debug_display {
+	    	println!("--------");
+	    }
+	    
+		println!("# started");
 	    
 	    self.update_possibilities();
-
 		let mut counter: usize = 0;
-
-	    while self.collapse() {
+		
+	    while self.collapse(debug_display) {
 	    	self.update_possibilities();
 	    	counter +=1;
 	    }
 
-		if display {
-		    println!("--------");
+	    let elapsed = now.elapsed();
 
-		    println!("finished with {} steps", counter);
+		if debug_display {
+	    	println!("--------");
+	    }
+	    println!("# finished in {} steps, {:.2?} ({:.2?}/step)", counter, elapsed, elapsed/(counter as u32));
+	    self.display(DisplayMode::Full);
+	}
 
-		    self.display();
+	fn ask(&mut self) {
+		for row_index in 0..self.size {
+			self.display(DisplayMode::Focus(row_index));
+			print!("> ");
+			let line: String = read!("{}\n");
+			for (column_index, c) in line.chars().enumerate() {
+			    match "0123456789abcdefghijklmnopqrstuvwxyz".find(c) {
+			        Some(value) => {
+			            if value <= self.size {
+			                self.grid[row_index][column_index].set(value);
+			            }
+			        }
+			        None => {}
+			    }
+			}
 		}
 	}
 }
 
-    	// [6,0,0,0,0,2,1,0,0], // has to backtrack
-    	// [0,3,2,9,0,0,0,7,0],
-    	// [0,0,0,0,0,8,0,0,0],
-    	// [2,0,0,0,0,0,4,0,0],
-    	// [7,0,3,0,0,0,9,1,0],
-    	// [0,8,0,0,9,4,0,0,0],
-    	// [0,0,4,0,0,0,6,0,0],
-    	// [1,2,0,7,0,0,0,0,5],
-    	// [0,0,0,0,0,0,0,9,4],
+fn to_base35(mut n: usize) -> String {
+    let chars = "0123456789abcdefghijklmnopqrstuvwxyz";
+    if n == 0 {
+        return chars[0..1].to_string(); // Special case for 0
+    }
 
+    let mut result = String::new();
+
+    while n > 0 {
+        let remainder = n % 35;
+        result.push(chars.chars().nth(remainder).unwrap());
+        n /= 35;
+    }
+
+    // The result will be in reverse order, so we need to reverse it
+    result.chars().rev().collect()
+}
 
 fn main() {
-    let sudoku_set: [[u8; 9]; 9] = [
-    	[0,0,0,0,0,0,0,0,0],
-    	[0,3,2,9,0,0,0,7,0],
-    	[0,0,0,0,0,8,0,0,0],
-    	[2,0,0,0,0,0,4,0,0],
-    	[7,0,3,0,0,0,9,1,0],
-    	[0,8,0,0,9,4,0,0,0],
-    	[0,0,4,0,0,0,6,0,0],
-    	[1,2,0,7,0,0,0,0,5],
-    	[0,0,0,0,0,0,0,9,4],
-    ];
+	let args: Vec<String> = env::args().collect();
+	if args.len() < 2 {
+	    eprintln!("Usage: {} <order> [--debug] [--ask]", args[0]);
+	    process::exit(1);
+	}
 
-    let mut sudoku = Sudoku::new(sudoku_set);
+	let size: usize = args[1].parse().unwrap_or_else(|_| {
+        eprintln!("Invalid size argument");
+        process::exit(1);
+    });
 
-	sudoku.solve(true);
+    let mut sudoku = Sudoku::new(min(size, 5));
+
+    if args.contains(&"--ask".to_string()) {
+    	sudoku.ask();
+    }
+    
+	sudoku.solve(args.contains(&"--debug".to_string()));
 }