diff --git a/src/utictactoe.c b/src/utictactoe.c
index aa03731..5bf1c3b 100644
--- a/src/utictactoe.c
+++ b/src/utictactoe.c
@@ -6,6 +6,11 @@
 #include <string.h>
 #include "utictactoe.h"
 
+#define OPTIONAL_ARGUMENT_IS_PRESENT \
+     ((optarg == NULL && optind < argc && argv[optind][0] != '-') \
+     ? (bool) (optarg = argv[optind++]) \
+     : (optarg != NULL))
+
 void help(){
     printf("usage: utictactoe ([-i LEVEL|-x N|-o N|-v|-V|-h] | -c FILE)\n");
     printf("Play a utictactoe game with human or program players.\n");
@@ -18,45 +23,82 @@ void help(){
     printf("-h, --help display this help and exit\n");
     printf("Tactics list: random (0), clever (1)\n");
 }
+
+int check_int_value ( char *value, int min, int max){
+    char * end_ptr;
+    int result;
+    result = strtol(optarg, &end_ptr, 10);
+    if ( strcmp(end_ptr, "\0") != 0 ) {
+        return -1;
+    }
+    if ( result < min || result > max) {
+        return -1;
+    }
+    return result;
+}
+
 int main(int argc, char* argv[]) {
     int optc;
+    int cross_ai, round_ai = 0;
     int inception_level = 0;
-    bool contest, round_ai, cross_ai  = false;
+    bool contest = false;
 
-    char * end_ptr;
     static struct option long_opts[] =
         {
           {"inception-level",   optional_argument,  0, 'i'},
-          {"cross-ai",          no_argument,        0, 'x'},
-          {"round-ai",          no_argument,        0, 'o'},
+          {"cross-ai",          required_argument,  0, 'x'},
+          {"round-ai",          required_argument,  0, 'o'},
           {"contest",           no_argument,        0, 'c'},
           {"verbose",           no_argument,        0, 'v'},
           {"version",           no_argument,        0, 'V'},
           {"help",              no_argument,        0, 'h'},
           {0, 0, 0, 0}
         };
-    while ((optc = getopt_long (argc, argv, "i:xocvVh", long_opts, NULL)) != -1){
+
+    while ((optc = getopt_long (argc, argv, "i::x:o:cvVh", long_opts, NULL)) != -1){
         switch (optc) {
         case 'i': /* 'a' option */
-            printf ("Inception activated\n");
-            if ( optarg ) {
-                inception_level = strtol(optarg, &end_ptr, 10);
-                assert ( strcmp(end_ptr,"\0") == 0);
-                assert ( inception_level >= 1 );
-                assert ( inception_level <= 3 );
+            if ( OPTIONAL_ARGUMENT_IS_PRESENT ) {
+                inception_level = check_int_value( optarg, 1, 3);
+                if ( inception_level == -1 ) {
+                    fprintf(stderr, "Error: incorrect inception level\n");
+                    exit (EXIT_FAILURE);
+                }
             }
             else {
                 inception_level = 2;
             }  
+            printf ("Inception activated, level: %d\n", inception_level);
             break;
         case 'x':
             printf ("cross ai\n");
-            cross_ai = true;
+            if ( optarg ) {
+                cross_ai = check_int_value(optarg, 0, 1);
+                if ( cross_ai == -1 ) {
+                    fprintf(stderr, "Error: incorrect cross ai value\n");
+                    exit (EXIT_FAILURE);
+                }
+            }
+            else {
+                fprintf(stderr, "Error: you must specify a value for cross ai\n");
+                exit (EXIT_FAILURE);
+            }
+
             break;
 
         case 'o':
             printf ("round ai\n");
-            round_ai = true;
+            if ( optarg ) {
+                round_ai = check_int_value(optarg, 0, 1);
+                if ( round_ai == -1 ) {
+                    fprintf(stderr, "Error: incorrect round ai value\n");
+                    exit (EXIT_FAILURE);
+                }
+            }
+            else {
+                fprintf(stderr, "Error: you must specify a value for round ai\n");
+                exit (EXIT_FAILURE);
+            }
             break;
 
         case 'c':
@@ -72,6 +114,7 @@ int main(int argc, char* argv[]) {
             exit(EXIT_SUCCESS);
         
         default:
+            fprintf(stderr, "Error: unknown option");
             exit (EXIT_FAILURE);
         }
     }