diff --git a/ES/Project/code.c b/ES/Project/code.c
index 03947eb..46f4be3 100644
--- a/ES/Project/code.c
+++ b/ES/Project/code.c
@@ -161,20 +161,31 @@ void lcd_print_str(const char *str) {
         lcd_data(*str++);
 }
 
-void lcd_print_num(unsigned int num, unsigned int base) {
+void lcd_print_num(int num, unsigned int base) {
     char buffer[17];
     int i = 0;
+    unsigned int unum;
 
-    if (num == 0) {
+    if (base == MODE_DEC) {
+        if (num < 0) {
+            lcd_data('-');
+            num = -num;
+        }
+    }
+
+    unum = (unsigned int)num;
+
+    if (unum == 0) {
         lcd_data('0');
         return;
     }
 
-    while (num > 0 && i < 16) {
-        unsigned int d = num % base;
+    while (unum > 0 && i < 16) {
+        unsigned int d = unum % base;
         buffer[i++] = (d < 10) ? ('0' + d) : ('A' + d - 10);
-        num /= base;
+        unum /= base;
     }
+
     while (i > 0)
         lcd_data(buffer[--i]);
 }
@@ -294,24 +305,36 @@ unsigned int is_valid_digit(unsigned int key) {
     return 1;
 }
 
-/* ===== Arithmetic ===== */
-unsigned int base_arith(unsigned int a, unsigned int b,
-                        unsigned int op, unsigned int base) {
-    unsigned int r;
+/* ===== Arithmetic per base (optimized) ===== */
+int base_arith(int a, int b, unsigned int op, unsigned int base) {
+    int r = 0;
+
     switch (op) {
         case OP_ADD:
             r = a + b;
             break;
+
         case OP_SUB:
-            r = (a >= b) ? (a - b) : 0;
+            r = a - b;
             break;
+
         case OP_MUL:
             r = a * b;
             break;
+
         default:
             r = a;
             break;
     }
+
+    // For non-decimal modes, keep everything positive and base-limited
+    if (base != MODE_DEC) {
+        if (r < 0)
+            r = ((r % base) + base) % base;
+        else
+            r = r % (base * base * base * base * base); // safe wraparound for multi-digit bases
+    }
+
     return r;
 }