diff --git a/firmware.asm b/firmware.asm
index b8f82d4..5b8307b 100644
--- a/firmware.asm
+++ b/firmware.asm
@@ -44,6 +44,9 @@
 .equ POLLING_STATE = 0x03
 .equ COMPLETION_STATE = 0x04
 
+.equ TRUE = 1
+.equ FALSE = 0
+
 .macro init_stack_p         ; Setup stack pointer
   ldi @0, low(@1)
   out SPL, @0
@@ -56,6 +59,9 @@
   pop r16
 .endm
 
+;
+; @0 - SRAM Address
+; @1 - Data to write
 .macro stsi                 ; Write to SRAM
   push r16
   ldi r16, @1
@@ -72,16 +78,51 @@
   pop r16
 .endm
 
+.macro set_btn_flag
+  push r16
+  ldi r16, @0
+  sts BTN_FLAGS_ADDRESS, r16
+  pop r16
+.endm
+
+.macro clr_btn_flag
+  push r16
+  lds r16, BTN_FLAGS_ADDRESS
+  cbr r16, @0
+  sts BTN_FLAGS_ADDRESS, r16
+  pop r16
+.endm
+
 .dseg                       ; Data segment
 .org	SRAM_START
 
+;
+; MCU Global states
 CURRENT_STATE_ADDRESS:  .byte	0x01
-PREVIOUS_STATE_ADDRESS: .byte 0x02
+PREVIOUS_STATE_ADDRESS: .byte 0x01
+
+;
+; Button flags
+BTN_FLAGS_ADDRESS: .byte 0x01
 
 .cseg                       ; Code segment
 .org 0x00                   ; Start program at 0x00
 
-setup:                      ; Setup program
+rjmp start
+rjmp PCINT4_ISR
+
+;
+; Interrupt service routines
+PCINT4_ISR:                 ; First button
+  set_btn_flag 0x01
+reti
+
+ldi r18, 0x00
+sts BTN_FLAGS_ADDRESS, r18
+
+;
+; Program start at reset
+start:
   init_stack_p r16, RAMEND  ; Init stack pointer of MCU
   set_state INIT_STATE      ; Turn MCU state to initialization
 
@@ -91,11 +132,21 @@ loop:                       ; Program loop
     cpi r16, INIT_STATE
     brne showing
     rcall MCU_Init
+    ; rcall delay_1s
     set_state SHOWING_STATE
   showing:                  ; Showing state
     cpi r16, SHOWING_STATE
     brne polling
-    rcall effect_1
+
+    lds r18, BTN_FLAGS_ADDRESS
+    cpi r18, 0x01
+    brne led_off
+    led_on:
+      sbi LED_PORT, 2
+      rcall delay_50ms
+      rjmp polling
+    led_off:
+      cbi LED_PORT, 2
   polling:                  ; Polling state
     cpi r16, POLLING_STATE
     brne completion
@@ -151,6 +202,36 @@ ret
 
 MCU_Init:
   rcall init_ports
+  rcall init_interrupts
+  rcall delay_before_start  ; Init MCU and delay before start main program
+ret
+
+delay_before_start:
+  ldi r17, 6
+  _init_loop_loading:
+    rcall effect_1
+    dec r17
+    brne _init_loop_loading
+  rcall delay_1s
+ret
+
+init_interrupts:
+  push r16
+
+  ;
+  ; Enable Port Change Interrupt
+  ldi r16, (1<<PCIE0)
+  out GIMSK, r16
+
+  ;
+  ; Set Pin Change Mask Register
+  ldi r16, (1<<PCINT4) | (1<<PCINT5) | (1<<PCINT6) | (1<<PCINT7)
+  out PCMSK0, r16
+  clr r16
+
+  sei                       ; Enable Global Interrupts
+
+  pop r16
 ret
 
 init_ports:                 ; Init MCU ports
@@ -169,20 +250,42 @@ init_ports:                 ; Init MCU ports
   pop r16
 ret 
 
-delay_50ms:
+delay_50ms:                 ; For 1MHz frequency
   push r18
   push r19
 
-  ldi r18, 65     ; 1c
-  ldi r19, 239     ; 1c
+  ldi r18, 65    
+  ldi r19, 239     
     _loop_d_50ms: 
-      dec  r19          ; 1c
-      brne _loop_d_50ms ; 2 or 1c = 665c
-      dec  r18          ; 1c
-      brne _loop_d_50ms ; 2 or 1c
+      dec  r19          
+      brne _loop_d_50ms 
+      dec  r18          
+      brne _loop_d_50ms 
       nop 
   pop r19
   pop r18              
 ret
 
+delay_1s:                   ; For 1MHz frequency 
+  .equ outer_count = 100
+  .equ inner_count = 2499
+
+  push r24
+  push r25
+
+  ldi r18, outer_count       
+    _reset:                   
+      ldi r24, low(inner_count)
+      ldi r25, high(inner_count)
+    _loop:                  
+      sbiw r24, 1             
+      brne _loop             
+
+      dec r18                 
+      brne _reset             
+      ldi r18, outer_count
+  pop r25
+  pop r24
+ret
+
 info: .db "Memory led game. Written by Sergey Yarkov 27.09.2021"
\ No newline at end of file
diff --git a/firmware.hex b/firmware.hex
index 374bfa1..184b198 100644
--- a/firmware.hex
+++ b/firmware.hex
@@ -1,18 +1,24 @@
 :020000020000FC
-:100000000FED0DBF0F9300916000009361000F93FF
-:1000100001E0009360000F910F91009160000130AA
-:1000200061F43AD00F9300916000009361000F9348
-:1000300002E0009360000F910F91023009F405D0A7
-:10004000033001F4043001F4E8CF1F932F933F9362
-:100050004F934BB30F9301EF0BBB0F9128D011E0DF
-:1000600033E020EF110F210F2BBB21D03A95C9F7B8
-:100070000F9308EF0BBB0F911AD018E033E020EF7D
-:100080001695210F2BBB13D03A95C9F74BBB4F9157
-:100090003F912F911F91089501D008950F930FE084
-:1000A0000ABB02950BBBBA9AC2980F9108952F9381
-:1000B0003F9321E43FEE3A95F1F72A95E1F70000EE
-:1000C0003F912F9108954D656D6F7279206C656435
-:1000D0002067616D652E205772697474656E2062A9
-:1000E0007920536572676579205961726B6F76204C
-:0A00F00032372E30392E3230323113
+:100000000AC000C00F9301E0009362000F911895A1
+:1000100020E0209362000FED0DBF0F930091600070
+:10002000009361000F9301E0009360000F910F9126
+:1000300000916000013061F441D00F9300916000A5
+:10004000009361000F9302E0009360000F910F9105
+:10005000023041F420916200213019F4DA9A4AD03A
+:1000600001C0DA98033001F4043001F4E1CF1F93AA
+:100070002F933F934F934BB30F9301EF0BBB0F9114
+:1000800039D011E033E020EF110F210F2BBB32D01C
+:100090003A95C9F70F9308EF0BBB0F912BD018E0DF
+:1000A00033E020EF1695210F2BBB24D03A95C9F7EA
+:1000B0004BBB4F913F912F911F91089512D008D0C3
+:1000C00001D0089516E0D3DF1A95E9F71FD00895FF
+:1000D0000F9300E10BBF00EF02BB002778940F9154
+:1000E00008950F930FE00ABB02950BBBBA9AC29812
+:1000F0000F9108952F933F9321E43FEE3A95F1F746
+:100100002A95E1F700003F912F9108958F939F93D7
+:1001100024E683EC99E00197F1F72A95D1F724E6DC
+:100120009F918F9108954D656D6F7279206C656414
+:100130002067616D652E205772697474656E206248
+:100140007920536572676579205961726B6F7620EB
+:0A01500032372E30392E32303231B2
 :00000001FF