Air Flip Drive (WIP)

Race as far as possible before running out of fuel!
Collect rings to gain turbo, then turbo-tackle into other vehicles to gain fuel.
Originally created for Extra Credits Game Design Jam. Still a work-in-progress (WIP).

Controls:
* Left or right arrow keys to steer.
* Down arrow to brake.
* While in air, press up or down arrow keys to glide up or dive respectively.
* While on ground, tap Z to bunny-hop.
* Hold X to use the turbo (works both on-ground and in-air). Requires turbo.
* Tap R to respawn at the middle of the track (early, if already off-track). This uses fuel.
* While on ground, hold Z to bunny-hop, then hold left or right arrow key to initiate drifting.
* One enters drift mode when white lines appear on the closest corner of the vehicle.  The trail particles on the ground will change as well.
* Once in drift mode, so long as the Z-key is held, the arrow keys can be let go.  In fact, they can now be used to adjust the trajectory of the drift.

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**Known Bugs:**

* Track can intersect itself, creating situations where it's impossible to progress.
* Track suddenly "despawns" below you if it loops under where you're driving.
* Bad camera.
* Vehicle falls through the track and other geometry.
* Sometimes, the vehicle will respawn for no reason.