This is my attempt at the AVR Pong final project.

https://wokwi.com/arduino/projects/294631094740845069

global main

.global __do_copy_data
#include <avr/io.h>  

; DOWN PIN6 = PD6
; UP PIN 7 = PD7
;
; CS PIN 10 (green) = PB2
CS = PB2
; IN PIN 11 = PB3
; CLK PIN 13 = PB5
;
;    [ "uno:10", "m1:CS", "green", [ "v-24", "*", "h-4" ] ],
;    [ "uno:11", "m1:DIN", "orange", [ "v-20", "*", "h-8" ] ],
;    [ "uno:13", "m1:CLK", "blue", [ "v-16", "*", "h-12" ] ],
;
.equ LED, PB5
BIT_UP = 7
BIT_DOWN = 6

#define tmpreg r16
#define tmpreg2 r17

#define TICKS r28
#define CLOCK Z

; Game status
  .data
  
paddle_player:
  .byte 0

paddle_comp:
  .byte 0

ball_x:
  .byte 0

ball_y:
  .byte 0

ball_dirx:
  .byte 0

ball_diry:
  .byte 0


  .text

init_game_status:
  ldi tmpreg, 4
  sts paddle_player, tmpreg

  inc tmpreg
  sts paddle_comp, tmpreg
  sts ball_y, tmpreg

  ldi tmpreg, 14
  sts ball_x, tmpreg

  ldi tmpreg, 0xff
  sts ball_dirx, tmpreg

  ldi tmpreg, 0xff
  sts ball_diry, tmpreg

  ret

clear_clock:
  clr TICKS
  ldi ZL, 0
  ldi ZH, 0
  ret

increment_clock:
  ;ADIW R30, 1
  ADIW Z, 1
  inc TICKS
  ret

.global TIMER1_OVF_vect
TIMER1_OVF_vect:
  push  r0
  in    r0, _SFR_IO_ADDR(SREG)
  push  r0
  rcall increment_clock

  pop r0
  out _SFR_IO_ADDR(SREG), r0
  pop r0
  reti


init_spi:
  ldi r24, (1<<5) | (1<<3) | (1<<2)
  out _SFR_IO_ADDR(DDRB), r24

  ldi  r24, (1<<2)
  out _SFR_IO_ADDR(PORTB),r24       ;   CS HIGH
  
  ldi  r24,0B01010001 
  out  _SFR_IO_ADDR(SPCR),r24
  ret

spi_wait:
      ; input r24
      ;break
      push r0
      out  _SFR_IO_ADDR(SPDR), r24
check_status:
      in r0,  _SFR_IO_ADDR(SPSR)
      sbrs r0, SPIF
      rjmp check_status

      pop r0
      ret

init_buttons:

  ; set as input
  ldi tmpreg, 0b11000000
  clr tmpreg
  out _SFR_IO_ADDR(DDRD), tmpreg

  ; enable pull up resistors
  ldi tmpreg, (1<<BIT_DOWN) | (1 << BIT_UP)
  out _SFR_IO_ADDR(PORTD), tmpreg

read_buttons:
  clr r16
  sbis _SFR_IO_ADDR(PIND), BIT_UP
  ldi r16,1
  sbis _SFR_IO_ADDR(PIND), BIT_DOWN
  ldi r16,2
  ret

update_paddles:
  push r16
  push r17

  ; move player paddles if buttons pressed
  rcall read_buttons
  cpi r16, 2
  brne nxt
  ; paddle down = inc
  lds r17, paddle_player
  inc r17
  cpi r17, 8
  brsh 2f
  sts paddle_player, r17
2:
  rjmp done

nxt:
  cpi r16, 1
  brne done

  lds r17, paddle_player
  tst r17
  breq done
  dec r17
  sts paddle_player, r17

done:
  ; computer paddles pseudo random
  mov r16, ZL
  andi r16, 0x7
  tst r16 
  brne 5f

  lds r17, paddle_comp

  ; randomize using clock upper byte
  mov r16, ZH
  andi r16, 0x7
  cpi r16, 0x4
  brsh 3f

  inc r17
  rjmp 4f

3:
  dec r17
4:
  andi r17, 0x7
  sts paddle_comp, r17

5:
  pop r17
  pop r16
  ret


test_draw_screen_pattern:
  cbi _SFR_IO_ADDR(PORTB),CS
  ldi r24, 1
  rcall spi_wait

  ldi r24, 0xaa
  rcall spi_wait

  ldi r24, 8
  rcall spi_wait

  ldi r24, 0xaa
  rcall spi_wait

  sbi _SFR_IO_ADDR(PORTB),CS 
  ret

draw_screen_row:
  ;r24 row 0 - TOP, row 7 - BOTTOM
  ;r22 left pattern
  ;r23 right pattern

  push r24
  inc r24
  push r1
  
  cbi _SFR_IO_ADDR(PORTB),CS
  mov r1, r24
  rcall spi_wait

  mov r24, r22
  rcall spi_wait

  mov r24, r1
  rcall spi_wait

  mov r24, r23
  rcall spi_wait
  sbi _SFR_IO_ADDR(PORTB),CS 

  pop r1
  pop r24
  ret

test_draw_screen_pattern2:
  ldi r24, 1
  ldi r22, 0x1
  ldi r23, 0x3
  rcall draw_screen_row

  ldi r24, 7
  ldi r22, 0x3
  ldi r23, 0x1
  rcall draw_screen_row
  ret

test_draw_screen_game:
  ldi r24, 3
  ldi r22, 6
  ldi r20, 8
  ldi r18, 6
  rcall draw_screen_game
  ret


is_paddle_row:

  ; r9 row tested
  ; r8 paddle middle
  
  push r0

  ;middle
  cp r8, r9
  breq 1f

  ;paddle top (-1)
  mov r0, r8
  dec r0
  cp r0, r9
  breq 1f

  ;paddle_bottom (+1)
  mov r0, r8
  inc r0
  cp r0, r9
1:
  pop r0
  ret


set_bit_16breg:
  ;input r0 = 0-15
  ;0 r22:r23  0x01:0x00
  ;1 r22:r23  0x02:0x00
  ;15 r22:r23 0x00:0x80

  push r16

  mov r16, r0
  ldi r22,1
1: 
  tst r16
  breq done_shifting

  lsl r22
  rol r23
  dec r16
  rjmp 1b

done_shifting:
  pop r16
  ret


draw_screen_game:
  ;input:
  ;r24 paddle_player
  ;r22 paddle_computer
  ;r20 ball_x 0..15
  ;r18 ball_y 0..7

  push r24
  push r22
  push r20
  push r18

  push r17
  push r16

  mov r0, r24
 mov...