Trying to create bash racing game

Question

I've already done some code, like I have a grid where I can freely move. But the behavior I want is to make the "road" move by itself while the "car" can move freely on the board to avoid some "rocks" placed randomly.

I want to create some kind of slot machine effect, when the start of the row is connected to it's end and it just endlessly scrolls. The move_up and move_down functions are supposed to be some kind of acceleration, but for now, it's just a simple rewrite from other movement functions.

I would appreciate your help, and if you can, please explain how exactly you achieved that results. Here is my code:

#!/bin/bash

# Constants
declare -A GRID
GRID_WIDTH=21
GRID_HEIGHT=15
CAR="▲"
ROCK="*"
CLEAR_SCREEN='\033[H\033[J'  # Clear the screen

# Initialize game variables
car_x=$((GRID_WIDTH / 2))
car_y=$((GRID_HEIGHT - 2))

init_grid() {
    # Initialize the grid
    for ((i=0; i < GRID_HEIGHT; i++)); do
        for ((j=0; j < GRID_WIDTH; j++)); do
            GRID[$i,$j]=" "
        done
    done
    
    GRID[0,0]="+"
    GRID[0,$((GRID_WIDTH-1))]="+"
    GRID[$((GRID_HEIGHT-1)),0]="+"
    GRID[$((GRID_HEIGHT-1)),$((GRID_WIDTH-1))]="+"
    GRID[$((GRID_HEIGHT-2)),$car_x]=$CAR
    GRID[5,5]=$ROCK
    
    for ((i=1; i < GRID_HEIGHT-1; i++)); do
        GRID[$i,0]="|"
        GRID[$i,$((GRID_WIDTH-1))]="|"
    done
    
    for ((i=1; i < GRID_WIDTH-1; i++)); do
        GRID[0,$i]="-"
        GRID[$((GRID_HEIGHT-1)),$i]="-"
    done
}

draw_grid() {
    # Draw the grid
    echo -e "$CLEAR_SCREEN"
    for ((i=0; i < GRID_HEIGHT; i++)); do
        for ((j=0; j < GRID_WIDTH; j++)); do
            printf "%s" "${GRID[$i,$j]}"
        done
        printf "\n"
    done
}

scroll_grid() {
    # Scroll the grid
    for ((i=1; i < GRID_HEIGHT-1; i++)); do
        for ((j=1; j < GRID_WIDTH-1; j++)); do
            GRID[$((i-1)),$j]=${GRID[$i,$j]}
        done
    done
}

move_left() {
    if ((car_x > 1)); then
        GRID[$car_y,$car_x]=" "
        ((car_x--))
        GRID[$car_y,$car_x]=$CAR
    fi
}

move_right() {
    if ((car_x < GRID_WIDTH-2)); then
        GRID[$car_y,$car_x]=" "
        ((car_x++))
        GRID[$car_y,$car_x]=$CAR
    fi
}

move_up() {
    if ((car_y > 1)); then
        GRID[$car_y,$car_x]=" "
        ((car_y--))
        GRID[$car_y,$car_x]=$CAR
    fi
}

move_down() {
    if ((car_y < GRID_HEIGHT-2)); then
        GRID[$car_y,$car_x]=" "
        ((car_y++))
        GRID[$car_y,$car_x]=$CAR
    fi
}

init_grid
while true; do
    draw_grid
    # sleep 0.5
    # scroll_grid
    
    read -rsn1 move
    case "$move" in
        "a") move_left ;;
        "d") move_right ;;
        "w") move_up ;;
        "s") move_down ;;
        "q") exit ;;
    esac
    
done