diff --git a/csts.cmi b/csts.cmi
index 138cc2c..a0fb49c 100644
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diff --git a/csts.cmx b/csts.cmx
index 9adfd61..07e0755 100644
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diff --git a/csts.ml b/csts.ml
index 4e01fb2..79d6855 100644
--- a/csts.ml
+++ b/csts.ml
@@ -12,11 +12,19 @@ let default_rect = {
   h = 0 ;
 } ;;
 
+(* graphing constants *)
 let __width__ = 1200
 and __height__ = 900 ;;
 let open_string = " 1200x900" ;;
 
+(* camera *)
 let camx = ref 0
 and camy = ref 0 ;;
 
-let sleep_d = 0.01 ;;
\ No newline at end of file
+(* time step *)
+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
diff --git a/csts.o b/csts.o
index 4e94ba8..0dad598 100644
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diff --git a/drawing.cmi b/drawing.cmi
index b12852f..35ff7c0 100644
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diff --git a/drawing.cmx b/drawing.cmx
index ba67b8b..c0210e0 100644
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diff --git a/drawing.ml b/drawing.ml
index 6621796..df6418b 100644
--- a/drawing.ml
+++ b/drawing.ml
@@ -129,6 +129,13 @@ let draw_letter x y c len = match c with
 
 let draw_string x0 y s len =
     let cur_x = ref x0 in
+    for i = 0 to String.length s -1 do
+        draw_letter !cur_x y s.[i] len;
+        cur_x := !cur_x + (len*10/7)
+    done;;
+
+let draw_string_centered x0 y s len =
+    let cur_x = ref (x0 - (len*10/7)*(int_of_float ((float_of_int (String.length s)) /. 2.))) in
     for i = 0 to String.length s -1 do
         draw_letter !cur_x y s.[i] len;
         cur_x := !cur_x + (len*10/7)
diff --git a/drawing.o b/drawing.o
index d964567..0105c31 100644
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diff --git a/dynamic.cmx b/dynamic.cmx
index a5e9210..ac45574 100644
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diff --git a/dynamic.o b/dynamic.o
index 188c60e..eb90e3c 100644
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diff --git a/main.cmi b/main.cmi
index ba264c0..3636734 100644
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diff --git a/main.cmx b/main.cmx
index f281aa9..6878c9b 100644
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diff --git a/main.o b/main.o
index 739d2db..1db3669 100644
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diff --git a/math b/math
index 0483fec..0817605 100755
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diff --git a/math.cmx b/math.cmx
index 991ac27..6a06f1e 100644
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diff --git a/math.o b/math.o
index a2203e2..987d55b 100644
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diff --git a/menus.cmi b/menus.cmi
index ff93623..2e6c492 100644
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diff --git a/menus.cmx b/menus.cmx
index 4fd46eb..d2dd277 100644
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diff --git a/menus.ml b/menus.ml
index 305b364..2959e86 100644
--- a/menus.ml
+++ b/menus.ml
@@ -119,6 +119,13 @@ let build_interface (title : string) (red : int) (green : int) (blue : int) (but
   Dynamic.dyn_add arr_interfaces res ;
   incr current_interface_index ;;
 
+let build_tweak (ptr : int ref) (m : int) (mx : int) (st : int) = {
+    ptr = ptr ;
+    min = m;
+    max = mx ;
+    pad = st ;
+  } ;;
+
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
 let current_it_id = ref 0 ;;
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
@@ -135,7 +142,15 @@ let add_button_to_current (b_id : int) =
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
 (* printing *)
 
+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 print_button (b : button) =
+  let (mx, my) = mouse_pos () in
+  if is_within b.pos mx my then begin
+    set_color (rgb 0 0 255) ;
+    fill_rect (b.pos.x-6) (b.pos.y-6) (b.pos.w+12) (b.pos.h+12) ;
+  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)) ;
@@ -154,15 +169,35 @@ let print_current_interface () =
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
 (* actions *)
 
-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 get1char () =
+  if key_pressed () then
+    read_key ()
+  else
+    '@' ;;
 
 let move_interface (b : button) = match b.actn with
   | Nothing -> ()
-  | Tweak (vc) -> begin
+  | Tweak val_ptr -> begin
     let halted = ref false in
+    set_line_width 3 ;
     while not !halted do
-      (* todo *)()
+      auto_synchronize false ;
+      set_color black ;
+      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_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 ;
+      Drawing.draw_integer_alignedleft (7*Csts.__width__/10-5-3*20*10/7) (Csts.__height__/2) val_ptr.max 18 ;
+      auto_synchronize true ;
+      Unix.sleepf Csts.sleep_d ;
+      match get1char () with
+        | '+' -> val_ptr.ptr := min val_ptr.max (!(val_ptr.ptr) + val_ptr.pad)
+        | '-' -> val_ptr.ptr := max val_ptr.min (!(val_ptr.ptr) - val_ptr.pad)
+        | '\n' | ' ' -> halted := true
+        | _ -> ()
     done
   end
   | Warp ne -> if ne = -1 then raise MenuExit else current_it_id := ne ;;
@@ -176,16 +211,25 @@ let action_on_button (mox : int) (moy : int) (b : button) =
   else 
     false ;;
 
+let stall = ref false ;;
+
 let action_on_interface () =
   if button_down () then begin
-    let (mox, moy) = mouse_pos () in
-    let rec aux = function
-      | [] -> ()
-      | b::t ->
-        if action_on_button mox moy b then () else aux t
-    in
-    aux (Dynamic.dyn_mem arr_interfaces !current_it_id).bts
-  end ;;
+    if !stall then 
+      () 
+    else begin
+      stall := true ;
+      let (mox, moy) = mouse_pos () in
+      let rec aux = function
+        | [] -> ()
+        | b::t ->
+          if action_on_button mox moy b then () else aux t
+      in
+      aux (Dynamic.dyn_mem arr_interfaces !current_it_id).bts
+    end
+  end 
+  else
+    stall := false ;;
   
 (* --------------------------------------------------------------------------------------------------------------------------------------------- *)
 (* Define the menu there *)
@@ -195,9 +239,9 @@ build_empty_interface "Options  " 32 32 32 ;;
 
 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 "Operations" {x = Csts.__width__/2 - 150; y = 380; w = 300; h = 100}  255 32 32 Nothing ;;
-build_button "Time"       {x = Csts.__width__/2 - 150; y = 270; w = 300; h = 100} 32 255 32 Nothing ;;
-build_button "Difficulty" {x = Csts.__width__/2 - 150; y = 160; w = 300; h = 100} 32 32 255 Nothing ;;
+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)) ;;
+build_button "Time"       {x = Csts.__width__/2 - 150; y = 270; w = 300; h = 100} 32 255 32 (Tweak (build_tweak Csts.time_to_ans 3 30 1)) ;;
+build_button "Difficulty" {x = Csts.__width__/2 - 150; y = 160; w = 300; h = 100} 32 32 255 (Tweak (build_tweak Csts.difficulty 1 10 1)) ;;
 build_button "Back"       {x = Csts.__width__/2 - 150; y = 50; w = 300; h = 100} 32 32 32 (Warp 0) ;;
 
 (*Printf.printf "(B : %d ; I : %d)\n" arr_buttons.len arr_interfaces.len ;;*)
diff --git a/menus.o b/menus.o
index 893524c..499d44d 100644
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