The latest build of Carpoon, which is up now, features:

•  Fuel gauge instead of text that says "FUEL: ##" 
• Holding down left click for longer carpoon shots!

I also added a red flash plus sound effect for a low fuel warning, but even then the player tow truck may have to flash too to make it more noticeable! Recalling the days of the NES Zelda low-hearts warning, I tried to make the sound not too irritating but maybe irritation is the key like Baby Mario crying in Yoshi's Island.

For the longer carpoon shots, I also factored in the player's speed but I'm finding this is making harpooning cars perpendicular to the player far more difficult. I'll likely tweak this to factor in player speed in harpoons moving closer to the front or back of the player, while not taking into account speed at the sides. If you have trouble with this too, let me know!