diff --git a/compilation.sh b/compilation.sh
index 55994f5..9bacd50 100644
--- a/compilation.sh
+++ b/compilation.sh
@@ -1,2 +1,2 @@
 rm *.cmi *.cmx
-ocamlfind ocamlopt -linkpkg -package unix -linkpkg -package graphics csts.ml dynamic.ml math.ml drawing.ml menus.ml  main.ml -o math
+ocamlfind ocamlopt -linkpkg -package unix -linkpkg -package graphics csts.ml dynamic.ml math.ml drawing.ml menus.ml maeth.ml main.ml -o math
diff --git a/csts.cmi b/csts.cmi
index a0fb49c..8af9521 100644
Binary files a/csts.cmi and b/csts.cmi differ
diff --git a/csts.cmx b/csts.cmx
index 07e0755..cae2103 100644
Binary files a/csts.cmx and b/csts.cmx differ
diff --git a/csts.ml b/csts.ml
index 79d6855..7a53619 100644
--- a/csts.ml
+++ b/csts.ml
@@ -27,4 +27,8 @@ let sleep_d = 0.01 ;;
 (* math *)
 let difficulty = ref 1 ;;
 let calc_length = ref 3 ;;
-let time_to_ans = ref 10 ;;
\ No newline at end of file
+let time_to_ans = ref 10 ;;
+
+let score = ref 0
+and combo = ref 0
+and max_combo = ref 0 ;;
\ No newline at end of file
diff --git a/csts.o b/csts.o
index 0dad598..1eafff9 100644
Binary files a/csts.o and b/csts.o differ
diff --git a/drawing.cmi b/drawing.cmi
index 35ff7c0..bb2d2ae 100644
Binary files a/drawing.cmi and b/drawing.cmi differ
diff --git a/drawing.cmx b/drawing.cmx
index c0210e0..9a0c149 100644
Binary files a/drawing.cmx and b/drawing.cmx differ
diff --git a/drawing.ml b/drawing.ml
index df6418b..cdf2851 100644
--- a/drawing.ml
+++ b/drawing.ml
@@ -1,6 +1,7 @@
 open Graphics ;;
+let fodder = ref 0 ;;
 
-let draw_integer x0 y n0 r =
+let draw_integer ?retval:(rv=fodder) x0 y n0 r =
   (* 7-seg display *)
   let n = ref n0 in
   let size = Math.ln_b 10 n0 in
@@ -30,9 +31,10 @@ let draw_integer x0 y n0 r =
           draw_poly_line [|(x-len/2 + !(Csts.camx), y-len + !(Csts.camy)); (x-len/2 + !(Csts.camx), y + !(Csts.camy))|];
 
       n := !n/10;
-  done ;;
+  done ;
+  rv := x0 + offset + size*(len*11/7) ;;
 
-let draw_integer_alignedleft x0 y n0 len =
+let draw_integer_alignedleft ?retval:(rv=fodder) x0 y n0 len =
   (* 7-seg display 2 *)
   set_line_width (max 1 (len/4));
   let n = ref n0 in
@@ -71,7 +73,8 @@ let draw_integer_alignedleft x0 y n0 len =
 
       n := !n/10;
       cur_x := !cur_x - (len*11/7);
-done ;;
+    done ;
+    rv := (x0 + (size+1)*(len*11/7)) ;;
 
 let decode_letter x y len arr =
   set_line_width 3;
diff --git a/drawing.o b/drawing.o
index 0105c31..5e5219c 100644
Binary files a/drawing.o and b/drawing.o differ
diff --git a/dynamic.cmx b/dynamic.cmx
index ac45574..70495ec 100644
Binary files a/dynamic.cmx and b/dynamic.cmx differ
diff --git a/dynamic.o b/dynamic.o
index eb90e3c..7a3f91d 100644
Binary files a/dynamic.o and b/dynamic.o differ
diff --git a/execution.sh b/execution.sh
index f7afc37..8c5d01f 100644
--- a/execution.sh
+++ b/execution.sh
@@ -1,3 +1,3 @@
 rm *.cmi *.cmx
-ocamlfind ocamlopt -linkpkg -package unix -linkpkg -package graphics csts.ml dynamic.ml math.ml drawing.ml menus.ml  main.ml -o math
+ocamlfind ocamlopt -linkpkg -package unix -linkpkg -package graphics csts.ml dynamic.ml math.ml drawing.ml menus.ml maeth.ml main.ml -o math
 ./math
\ No newline at end of file
diff --git a/maeth.cmi b/maeth.cmi
new file mode 100644
index 0000000..a4c9a50
Binary files /dev/null and b/maeth.cmi differ
diff --git a/maeth.cmx b/maeth.cmx
new file mode 100644
index 0000000..1476a5f
Binary files /dev/null and b/maeth.cmx differ
diff --git a/maeth.ml b/maeth.ml
new file mode 100644
index 0000000..7d159c5
--- /dev/null
+++ b/maeth.ml
@@ -0,0 +1,120 @@
+open Graphics ;;
+Random.self_init () ;;
+
+type operation =
+  Val of int |
+  Sum of operation * operation |
+  Diff of operation * operation |
+  Prod of operation * operation |
+  Exp of operation * int ;;
+
+let rec calculate = function
+  | Val k -> k
+  | Exp (op, k) -> Math.pw (calculate op) k
+  | Sum (f, g) -> (calculate f) + (calculate g)
+  | Diff (f, g) -> (calculate f) - (calculate g)
+  | Prod (f, g) -> (calculate f) * (calculate g) ;;
+
+let generate_random_calc ?plus_w:(pw=10) ?minus_w:(mw=8) ?prod_w:(uw=2) ?exp_w:(ew=0) (length : int) (inf : int) (sup : int) =
+  let sum = pw + mw + uw + ew in
+  let rec aux = function
+    | 0 | 1 -> 
+      Val (inf + Random.int (sup - inf))
+    | k -> 
+      let r = Random.int sum in 
+      if r < pw then begin
+        if Random.int 2 = 0 then
+          Sum(aux 0, aux (k-1))
+        else
+          Sum(aux (k-1), aux 0)
+      end
+      else if r < pw+mw then begin
+        if Random.int 2 = 0 then
+          Diff(aux 0, aux (k-1))
+        else
+          Diff(aux (k-1), aux 0)
+      end
+      else if r < pw+mw+uw then begin
+        if Random.int 2 = 0 then
+          Prod(aux 0, aux (k-1))
+        else
+          Prod(aux (k-1), aux 0)
+      end
+      else begin
+        Exp(aux (k-1), 2 + Random.int 2)
+      end
+  in
+  aux length ;;
+
+let draw_bracket_open ?retval:(rv=Drawing.fodder) (x : int) (y : int) (size : int) =
+  moveto (x + size/4) (y+5*size/4) ;
+  lineto (x) (y+size/2) ;
+  lineto (x) (y-size/2) ;
+  lineto (x + size/4) (y-5*size/4) ;
+  rv := x + size/4 +6 ;;
+
+let draw_bracket_close ?retval:(rv=Drawing.fodder) (x : int) (y : int) (size : int) =
+  moveto (x) (y+5*size/4) ;
+  lineto (x + size/4) (y+size/2) ;
+  lineto (x + size/4) (y-size/2) ;
+  lineto (x) (y-5*size/4) ;
+  rv := x + size/4 +6 ;;
+
+let draw_sign ?retval:(rv=Drawing.fodder) (x : int) (y : int) (len : int) = function
+  | '+' ->
+    draw_poly_line [|(x, y); (x + len, y)|] ;
+    draw_poly_line [|(x+len/2, y + len/2); (x+len/2, y - len/2)|] ;
+  | '-' ->
+    draw_poly_line [|(x, y); (x + len, y)|] ;
+  | 'x' ->
+    Drawing.draw_letter x y 'x' len ;
+  | _ -> failwith "incorrect\n" ;;
+
+let require_bracket = function
+    | Val _ -> false
+    | _ -> true ;;
+
+let print_calc (f : operation) (x0 : int) (y0 : int) (size : int) =
+  set_line_width 3 ;
+  set_color black ;
+  let x = ref x0 in
+  let rec aux = function
+    | Val k -> 
+      Drawing.draw_integer_alignedleft !x y0 k size ~retval:x ;
+      (*Printf.printf "%d --> \n" !x ;*)
+    | Exp (f, k) -> ()
+    | Sum (f, g) ->
+      if require_bracket f then draw_bracket_open !x y0 size ~retval:x ;
+      aux f ;
+      if require_bracket f then draw_bracket_close !x y0 size ~retval:x ;
+
+      draw_sign !x y0 size '+' ~retval:x ;
+      x := !x + size*10/7 ;
+      
+      if require_bracket g then draw_bracket_open !x y0 size ~retval:x ;
+      aux g ;
+      if require_bracket g then draw_bracket_close !x y0 size ~retval:x ;
+    | Diff (f, g) ->
+      if require_bracket f then draw_bracket_open !x y0 size ~retval:x ;
+      aux f ;
+      if require_bracket f then draw_bracket_close !x y0 size ~retval:x ;
+
+      draw_sign !x y0 size '-' ~retval:x ;
+      x := !x + size*10/7 ;
+
+      if require_bracket g then draw_bracket_open !x y0 size ~retval:x ;
+      aux g ;
+      if require_bracket g then draw_bracket_close !x y0 size ~retval:x ;
+    | Prod (f, g) ->
+      if require_bracket f then draw_bracket_open !x y0 size ~retval:x ;
+      aux f ;
+      if require_bracket f then draw_bracket_close !x y0 size ~retval:x ;
+
+      draw_sign !x y0 (size/2) 'x' ~retval:x ;
+      x := !x + size*10/7 ;
+
+      if require_bracket g then draw_bracket_open !x y0 size ~retval:x ;
+      aux g ;
+      if require_bracket g then draw_bracket_close !x y0 size ~retval:x ;
+  in
+  aux f ;;
\ No newline at end of file
diff --git a/maeth.o b/maeth.o
new file mode 100644
index 0000000..2b2da2f
Binary files /dev/null and b/maeth.o differ
diff --git a/main.cmi b/main.cmi
index 3636734..7eb4cdc 100644
Binary files a/main.cmi and b/main.cmi differ
diff --git a/main.cmx b/main.cmx
index 6878c9b..dc512ff 100644
Binary files a/main.cmx and b/main.cmx differ
diff --git a/main.ml b/main.ml
index c77ce52..9d1006f 100644
--- a/main.ml
+++ b/main.ml
@@ -1,17 +1,26 @@
 open Graphics ;;
-
 Random.self_init () ;;
 
 let mainloop () =
   open_graph Csts.open_string ;
   set_window_title "Maeth";
-  while true do 
-    auto_synchronize false ;
-    clear_graph () ;
-    Menus.print_current_interface () ;
-    auto_synchronize true ;
-    Menus.action_on_interface () ;
-    Unix.sleepf Csts.sleep_d
-  done ;;
+  try
+    while true do 
+      auto_synchronize false ;
+      clear_graph () ;
+      Menus.print_current_interface () ;
+      auto_synchronize true ;
+      Menus.action_on_interface () ;
+      Unix.sleepf Csts.sleep_d
+    done ;
+    ()
+  with
+    | Menus.MenuStart ->
+      clear_graph () ;
+      Maeth.print_calc (Maeth.generate_random_calc 8 1 20) (10) (Csts.__height__/2) 20 ;
+      while true do
+        Unix.sleepf Csts.sleep_d
+      done ;;
+
 
 mainloop () ;;
\ No newline at end of file
diff --git a/main.o b/main.o
index 1db3669..0d688fc 100644
Binary files a/main.o and b/main.o differ
diff --git a/math b/math
index 0817605..b2ac13c 100755
Binary files a/math and b/math differ
diff --git a/math.cmx b/math.cmx
index 6a06f1e..210928b 100644
Binary files a/math.cmx and b/math.cmx differ
diff --git a/math.o b/math.o
index 987d55b..b25fa5e 100644
Binary files a/math.o and b/math.o differ
diff --git a/menus.cmi b/menus.cmi
index 2e6c492..6f9a376 100644
Binary files a/menus.cmi and b/menus.cmi differ
diff --git a/menus.cmx b/menus.cmx
index d2dd277..22d9be9 100644
Binary files a/menus.cmx and b/menus.cmx differ
diff --git a/menus.ml b/menus.ml
index 2959e86..0acd1c2 100644
--- a/menus.ml
+++ b/menus.ml
@@ -1,5 +1,6 @@
 open Graphics ;;
 exception MenuExit ;;
+exception MenuStart ;;
 
 let current_button_index = ref 0
 and current_interface_index = ref 0 ;;
@@ -145,6 +146,12 @@ let add_button_to_current (b_id : int) =
 let is_within (r : Csts.rect) (x : int) (y : int) =
   r.x <= x && r.y < y && x <= r.x + r.w && y <= r.y + r.h ;;
 
+let draw_closest (r : int) (g : int) (b : int) =
+  if r+g+b <= 384 then
+    set_color white
+  else
+    set_color black ;;
+
 let print_button (b : button) =
   let (mx, my) = mouse_pos () in
   if is_within b.pos mx my then begin
@@ -153,17 +160,19 @@ let print_button (b : button) =
   end;
   set_color (rgb b.red b.green b.blue) ;
   fill_rect b.pos.x b.pos.y b.pos.w b.pos.h ;
-  set_color (rgb (255 - b.red) (255 - b.green) (255 - b.blue)) ;
+  draw_closest b.red b.green b.blue ;
   set_line_width 2 ;
   Drawing.draw_string (b.pos.x+3) (b.pos.y + b.pos.h/2) b.text (min (3*b.pos.h/4-2) ((7*(b.pos.w*3/4-4)/(max 1 (String.length b.text)))/10)) ;;
 
 let print_interface (it : interface) =
   List.iter print_button it.bts ;
+  set_color black ;
   Drawing.draw_string 20 (Csts.__height__ - 40) it.title 30 ;;
 
 let print_current_interface () =
   let interf = Dynamic.dyn_mem arr_interfaces !current_it_id in
   List.iter print_button interf.bts ;
+  set_color black ;
   Drawing.draw_string 20 (Csts.__height__ - 40) interf.title 30 ;;
 
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
@@ -186,7 +195,7 @@ let move_interface (b : button) = match b.actn with
       fill_rect (3*Csts.__width__/10) (3*Csts.__height__/10) (2*Csts.__width__/5) (2*Csts.__height__/5) ;
       set_color white ;
       Drawing.draw_string_centered (Csts.__width__/2) (13*Csts.__height__/20) b.text 20 ;
-      Drawing.draw_integer (5+Csts.__width__/2) (Csts.__height__/2) !(val_ptr.ptr) 40 ;
+      Drawing.draw_integer (5+Csts.__width__/2) (Csts.__height__/2) !(val_ptr.ptr) 60 ;
       Drawing.draw_string (5+3*Csts.__width__/10) (11*Csts.__height__/20) "Min" 20 ;
       Drawing.draw_integer_alignedleft (5+3*Csts.__width__/10) (Csts.__height__/2) val_ptr.min 18 ;
       Drawing.draw_string (7*Csts.__width__/10-5-3*20*10/7) (11*Csts.__height__/20) "Max" 20 ;
@@ -200,7 +209,13 @@ let move_interface (b : button) = match b.actn with
         | _ -> ()
     done
   end
-  | Warp ne -> if ne = -1 then raise MenuExit else current_it_id := ne ;;
+  | Warp ne ->
+    if ne = -1 then 
+      raise MenuExit 
+    else if ne = -2 then
+      raise MenuStart
+    else
+      current_it_id := ne ;;
 
 let action_on_button (mox : int) (moy : int) (b : button) =
   if is_within b.pos mox moy then begin
@@ -237,6 +252,7 @@ let action_on_interface () =
 build_empty_interface "Main Menu" 128 128 128 ;;
 build_empty_interface "Options  " 32 32 32 ;;
 
+build_button "Start"      {x = Csts.__width__/2 - 150; y = 270; w = 300; h = 100} 32 255 32 (Warp (-2)) ;;
 build_button "Options"    {x = Csts.__width__/2 - 150; y = 160; w = 300; h = 100} 255 32 255 (Warp 1) ;;
 build_button "Exit"       {x = Csts.__width__/2 - 150; y = 50; w = 300; h = 100} 1 1 1 (Warp (-1)) ;;
 build_button "Length"     {x = Csts.__width__/2 - 150; y = 380; w = 300; h = 100}  255 32 32 (Tweak (build_tweak Csts.calc_length 2 20 1)) ;;
@@ -247,7 +263,8 @@ build_button "Back"       {x = Csts.__width__/2 - 150; y = 50; w = 300; h = 100}
 (*Printf.printf "(B : %d ; I : %d)\n" arr_buttons.len arr_interfaces.len ;;*)
 add_button_to_interface 0 0 ;
 add_button_to_interface 0 1 ;
-add_button_to_interface 1 2 ;
+add_button_to_interface 0 2 ;
 add_button_to_interface 1 3 ;
 add_button_to_interface 1 4 ;
-add_button_to_interface 1 5 ;
\ No newline at end of file
+add_button_to_interface 1 5 ;
+add_button_to_interface 1 6 ;
\ No newline at end of file
diff --git a/menus.o b/menus.o
index 499d44d..9943652 100644
Binary files a/menus.o and b/menus.o differ