If you move the mouse really fast over the lines, then the collision isn't detected - really really easy to cheat with this. Rather than detecting if the mouse is over the green line, you should ensure that an imaginary line between the mouse's current position and its previous position doesn't cross any line - that way this cheat would be removed.
When you hold down a key on the keyboard while in a textbox, you get a delay between the first and subsequent keys that appear. You don't want that delay crossing over into the movement of your ship, which it has here. You should handle "on mouse down" rather than "on key pressed" to move the ship, that way it won't be jerky.
Also, because the game is controlled exclusively by the keyboard, you should never have to move the mouse - having to move the mouse just to click retry is annoying. You should be able to use the keyboard to retry the game.
It was WAY too easy... once I spent 5 minutes trying to work out how to shoot the gun... please put "click the mouse to fire the gun" in the instructions!!
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Thank you. I am in the process of making a second one and i will take this and other comments into consideration.