DE2 push buttons question

I have a simple counter in VHDL for DE2-115 (should work with any DE2). KEY0 starts counting, KEY1 stops, KEY2 resets. The output is displayed on 7-seg LEDs HEX0 - HEX3 in hexa digits (to be simple manner).

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity led_counter_ent is
    port (     CLOCK_50: in std_logic;
--            LEDR    : out std_logic_vector(15 downto 0);
            HEX0    : out std_logic_vector(6 downto 0);
            HEX1    : out std_logic_vector(6 downto 0);
            HEX2    : out std_logic_vector(6 downto 0);
            HEX3    : out std_logic_vector(6 downto 0);
            HEX4    : out std_logic_vector(6 downto 0) := (others => '1');
            HEX5    : out std_logic_vector(6 downto 0) := (others => '1');
            HEX6    : out std_logic_vector(6 downto 0) := (others => '1');
            HEX7    : out std_logic_vector(6 downto 0) := (others => '1');
            KEY        : in std_logic_vector(3 downto 0);
            LEDG    : out std_logic_vector(1 downto 0));
end led_counter_ent;
architecture behavior of led_counter_ent is
signal count    : std_logic_vector(24 downto 0) := (others => '0');
signal beat_count: std_logic_vector(15 downto 0) := (others => '0');
signal run        : std_logic                        := '0';
signal reset    : std_logic                        := '0';
procedure segment_proced (signal data : in std_logic_vector(3 downto 0); signal digit : out std_logic_vector(6 downto 0)) is
begin                          
    case data is
        when "0000" => digit <= "1000000"; -- 0
        when "0001" => digit <= "1111001"; -- 1
        when "0010" => digit <= "0100100"; -- 2
        when "0011" => digit <= "0110000"; -- 3
        when "0100" => digit <= "0011001"; -- 4
        when "0101" => digit <= "0010010"; -- 5
        when "0110" => digit <= "0000010"; -- 6
        when "0111" => digit <= "1111000"; -- 7
        when "1000" => digit <= "0000000"; -- 8
        when "1001" => digit <= "0010000"; -- 9
        when "1010" => digit <= "0001000"; -- A
        when "1011" => digit <= "0000011"; -- b
        when "1100" => digit <= "1000110"; -- C
        when "1101" => digit <= "0100001"; -- d
        when "1110" => digit <= "0000110"; -- E
        when "1111" => digit <= "0001110"; -- F
        when others => digit <= "1111111"; -- switch off
    end case;
end segment_proced;
    
begin
    buttons_process:process (key(0), key(1), key(2), key(3))
    begin
        -- signals run and reset are set due the first expression in the process - why ??
            if (key(1) = '0') then
                run <= '0';
                hex5    <= "1000000"; -- 0
            else    
                hex5    <= "1111001"; -- 1
            end if;
            
            if (key(0) = '1') then
                hex4    <= "1111001"; -- 1
            else
                hex4    <= "1000000"; -- 0
                reset <= '0';
                run <= '1';
                --run <= not run; -- switch ON/OFF does't work properly - why ??
            end if;
            
            if (key(3) = '0') then
                hex7    <= "1000000"; -- 0
                run <= not run; -- switch ON/OFF does't work properly - why ??
            else    
                hex7    <= "1111001"; -- 1
            end if;
            
            if (key(2) = '0') then
                hex6    <= "1000000"; -- 0
                reset <= '1';
            else
                hex6    <= "1111001"; -- 1
            end if;
    end process;
    counter_process:process (clock_50)
    begin
        if clock_50 = '1' and clock_50'event then
            count <= count + 1;
            --if count = "1111111111001011010000000" then -- 33.527.424
            --if count = "111111111001011010000000" then -- 16.750.208
            --if count = "110110001001011010000000" then -- 14.194.304
            --if count = "100110001001011010000000" then -- 10.000.000 - 200ms
            if count = "10011000100101101000000" then -- 5.000.000 - 100ms
            --if count = "111101000010010000000" then -- 2.000.000 - 40ms
            --if count = "1111010000100100000" then -- 500.000 - 10ms
            --if count = "1111010000100011111" then -- 499.999 - 10ms proper
                count    <= (others => '0');
--                tik <= not tik;
                if (run = '1') then
                    beat_count <= beat_count + 1;
                end if;
                if (reset = '1') then
                    beat_count <= (others => '0');
                end if;
            end if;
        end if;
    end process;    
    
    segment_proced(beat_count(3 downto 0), hex0);
    segment_proced(beat_count(7 downto 4), hex1);
    segment_proced(beat_count(11 downto 8), hex2);
    segment_proced(beat_count(15 downto 12), hex3);
    
--    ledr <= beat_count;
    ledg(0) <= run;
    ledg(1) <= reset;
                
end behavior;

run <= not run;