Marble line

Hello everyone,

I am trying to make a marble line. I have red marbles and blue marbles and I basically want to fill in order an integer vector with the value 2 for blue marbles, 1 for red marbles and 0 for when there are no marbles. The way I want this to work is that I want to start with an empty line and, every time I press a button called redMarble, a red marble will go to the first empty space of this line and every time I press the blueMarble button, a blue marble will go to the first empty space available of the line. The vector that represent the line is called marbleLine, and I made it in a way that I can change its size if I want.

Unfortunately though, I have not been able to get this right. I have gone through it over and over again but I can't find what I am doing wrong or another way to do what I want.

The code I have so far is:

library IEEE;
use IEEE.std_logic_1164.all;
Entity Central is
    generic (N: integer := 9);
    port(
        redMarble, blueMarble: in std_logic;
        -- outLine is here just for tests
        outLine: out std_logic_vector(N downto 0)
        );
        
end Central;
architecture archC of Central is 
    type Vector is array (N downto 0) of integer range 0 to 2;
    signal marbleLine : Vector;
    begin 
        process(redMarble, blueMarble) is
        variable alreadyFoundFirstZero: std_logic;
        begin
        
        alreadyFoundFirstZero := '0';
        if(rising_edge(redMarble)) then
-- Here I will look for the first empty space, or 0, in the marbleLine
            for i in 0 to N loop
                if(alreadyFoundFirstZero = '0') then
                    if(marbleLine(i) = 0) then
                        marbleLine(i) <= 1;
                        alreadyFoundFirstZero := '1';
                    end if;
                end if;
            end loop;
        end if;
        alreadyFoundFirstZero := '0';
        if(rising_edge(blueMarble)) then
            for i in 0 to N loop
                if(alreadyFoundFirstZero = '0') then
                    if(marbleLine(i) = 0) then
                        marbleLine(i) <= 2;
                        alreadyFoundFirstZero := '1';
                    end if;
                end if;
            end loop;
        end if;
        end process;
        
        
        -- Testing Output
        process(marbleLine) is
        begin
            for i in 0 to N loop
                if (marbleLine(i)= 1) then
                    outLine(i) <= '1';
                end if;
                if (marbleLine(i)= 2) then
                    outLine(i) <= '0';
                end if;
            end loop;
        end process;
        
end archC;

With this code I am getting multiple erros of the kind:

Error (10821): HDL error at Central.vhd(34): can't infer register for "marbleLine[0][0]" because its behavior does not match any supported register model

and

Error (10820): Netlist error at Central.vhd(34): can't infer register for marbleLine[1][0] because its behavior depends on the edges of multiple distinct clocks

Does anyone know how to fix these problems, or even, how to make this possible in a different way?

Thank you all in advance,

Stomp