"diagonal line"

not vertically locked, just a test
also not the whole screen, just a bit

main.S

@@ -2,9 +2,13 @@
 #include "macro.h"
 
 .data
+
 status:
 .byte 0x0
 
+offset:
+.byte 78
+
 .text
 
 .global main_s
@@ -64,7 +68,17 @@ wait2:
 
 .global int0_handler
 int0_handler:
-    ldi r31, 80
+    push r31
+    in r31, IO(SREG)    ; status register
+    push r31
+
+    lds r31, offset
+    dec r31
+    cpi r31, 1
+    brne 1f
+    ldi r31, 78
+1:
+    sts offset, r31
 loop:
     dec r31
     brne loop
@@ -85,5 +99,8 @@ loop:
     nop
     cbi IO(PORTB), 4
 1:
+    pop r31
+    out IO(SREG), r31
+    pop r31
+    reti
 
-    ret

main.c

@@ -4,8 +4,18 @@
 void main_s(void);
 void int0_handler(void);
 
-ISR(INT0_vect) {
-    int0_handler();
+void pippo() {
+    asm("nop");
+    asm("push r1");
+    int i = 0;
+    i = 2;
+    i += 1;
+    reti();
+}
+
+
+ISR(INT0_vect, ISR_NAKED) {
+    asm("jmp int0_handler");
 }
 
 int main() {