Problem with 2D side scrolling jump function

[alasqa]

Hey yo I'm working on a space adventure/2D side scroller and I am now having issues with my jump code. I can get the character to jump with the following code, but instead of jumping upwards, my character jumps downward. I have messed around with it for a while changing the variables to negative and what not. Still to no avail. I followed a tutorial online and got the following code.

This section is in the update function:

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if player.y_velocity ~= 0 then 
        player.y = player.y + player.y_velocity * dt 
        player.y_velocity = player.y_velocity - gravity * dt
        if player.y < 535 then 
            player.y_velocity = 0
            player.y = 535
        end
    end

This section of code is in the keypressed function:

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if key == " " then
		if player.y_velocity == 0 then
			player.y_velocity = jump_height
		end
	end

Now before I took the code straight from the tutorial I had it written out on my own. That didn't work so I went ahead and just tried to copy and paste it and just adjust a few numbers. That didn't work either. Anyone have any ideas whats going on or have a better way to implement jumping into a game.

[alasqa]

Okay well I fixed the problem, turns out I had missed one vital part of the code.

I had to make sure to put a negative next to the player.y variable

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loveg.draw(player.image, player.x, - player.y, 0, 1, 1)

However, this causes another issue. I have my player.y set to 535, so when it goes negative, it goes off the screen. This is the only fix I could find for the upwards jumping. Any ideas on how to fix this next issue?

[micha]

Better use positive coordinates:

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loveg.draw(player.image, player.x, - player.y, 0, 1, 1)

and reverse the sign of gravity and jump hight.