function init_player()
    setchar(244, 0x00, 0x00, 0x00, 0x00, 0x18, 0x7E, 0xFF, 0xFF)
    player = {
        x = 10,
        y = 14
    }
end

function init_bullet()
    setchar(145, 0x08, 0x10, 0x08, 0x10, 0x08, 0x10, 0x08, 0x10)
    bullet = {
        x = 0,
        y = 0,
        enabled = false
    }
end

function init_explosion()
    setchar(146, 0x10, 0x54, 0x28, 0xC6, 0x28, 0x54, 0x10, 0x00)
    explosion = {
        x = 0,
        y = 0,
        enabled = false,
        counter = 0
    }
end

function init_enemies()
    setchar(16, 0x7E, 0xDB, 0xFF, 0x66, 0x3C, 0x66, 0x81, 0x00)
    -- setchar(16, 0x7E, 0xDB, 0x66, 0x3C, 0x66, 0x81, 0x66, 0x00)
    enemies = {}
    local index = 1
    for i = 1, 8 do
        for j = 1, 5 do
            local e = {
                x = (i * 2),
                y = j + 1,
                enabled = true
            }
            enemies[index] = e
            index = index + 1
        end
    end
    enemy_desp = 1
    enemy_speed = 80
end

function create_bullet(x, y)
    bullet.x = x
    bullet.y = y
    bullet.enabled = true
end

function delete_bullet()
    bullet.enabled = false
end

function create_explosion(x, y)
    explosion.x = x
    explosion.y = y
    explosion.enabled = true
    explosion.counter = 50
end

function delete_explosion()
    explosion.enabled = false
end

function update_player()
    if clock % 5 == 0 then
        -- dreta
        if btn(KEY_RIGHT) and player.x < 19 then
            player.x = player.x + 1
        end

        -- esquerra
        if btn(KEY_LEFT) and player.x > 0 then
            player.x = player.x - 1
        end
    end

    -- dispara
    if btn(KEY_SPACE) and bullet.enabled == false then
        create_bullet(player.x, player.y - 1)
    end

    -- reset
    if btn(KEY_R) then
        init()
    end
end

function update_enemies()
    if clock % enemy_speed == 0 then
        sound(80, 50)
        local border_reached = false
        if enemy_desp ~= 0 then -- moviment horitzontal
            for i = 1, #enemies do
                if enemies[i].enabled == true then
                    enemies[i].x = enemies[i].x + enemy_desp
                    if enemies[i].x == 0 or enemies[i].x == 19 then
                        border_reached = true
                    end
                end
            end
            if border_reached == true then
                last_enemy_desp = enemy_desp
                enemy_desp = 0
            end
        elseif enemy_desp == 0 then -- moviment vertical
            for i = 1, #enemies do
                if enemies[i].enabled == true then
                    enemies[i].y = enemies[i].y + 1
                end
            end
            enemy_desp = -last_enemy_desp
        end
    end
end

function update_bullet()
    if clock % 10 == 0 and bullet.enabled == true then
        bullet.y = bullet.y - 1
        if bullet.y == 0 then
            delete_bullet()
        end
        for i = 1, #enemies do
            if enemies[i].enabled == true then
                if bullet.y == enemies[i].y and bullet.x == enemies[i].x then
                    create_explosion(bullet.x, bullet.y)
                    delete_bullet()
                    enemies[i].enabled = false
                    score = score + 10
                    sound(400, 40)
                    enemy_speed = enemy_speed - 2
                end
            end
        end
    end
end

function update_explosion()
    if explosion.enabled == true then
        if explosion.counter > 0 then
            explosion.counter = explosion.counter - 1
        else
            delete_explosion()
        end
    end
end

function draw_player()
    ink(COLOR_GREEN)
    paper(COLOR_BLACK)
    print("\244", player.x, player.y)
end

function draw_enemies()
    ink(COLOR_LIGHT_GREEN)
    paper(COLOR_BLACK)
    for i = 1, #enemies do
        if enemies[i].enabled == true then
            print("\16", enemies[i].x, enemies[i].y)
        end
    end
end

function draw_bullet()
    if bullet.enabled == true then
        ink(COLOR_CYAN)
        paper(COLOR_BLACK)
        print("\145", bullet.x, bullet.y)
    end
end

function draw_explosion()
    if explosion.enabled == true then
        ink(COLOR_RED)
        paper(COLOR_BLACK)
        print("\146", explosion.x, explosion.y)
    end
end

function draw_hud()
    ink(COLOR_LIGHT_GRAY)
    paper(COLOR_BLACK)
    print("                    ", 0, 0)
    print("SCORE: ", 0, 0)
    print(score, 6, 0)
end

function draw_debug()
    ink(COLOR_BLACK)
    paper(COLOR_WHITE)
    locate(0, 0)
    print(player.x)
end

function init()
    mode(2)
    clock = 0
    score = 0
    paper(COLOR_BLACK)
    ink(COLOR_RED)
    init_player()
    init_enemies()
    init_bullet()
    init_explosion()
end

function update()
    clock = clock + 1

    update_player()
    update_enemies()
    update_bullet()
    update_explosion()

    paper(COLOR_BLACK)
    cls()

    draw_player()
    draw_enemies()
    draw_bullet()
    draw_explosion()
    draw_hud()
    -- draw_debug()
end