I posted updated code to the Files section above. This release incorporates some of the suggestions made last Sunday at the Retro Computer meetup.

1. Increase the initial allotment of fuel from 999 to 1,999. Correspondingly the fuel bonus for a successful landing and penalty for a crash have been increased from 50 to 100 in both cases. 
2. Changed the scoring so that if you crash inside a landing zone, the multiplier for that zone is applied to the 5 points already being added.  This corresponds to the "hard landing" bonus awarded in the original arcade but without the velocity check. It also encourages an end game strategy of trying to hit landing zones when there is not enough fuel left for a safe landing.
3. A small change to show the multiplier label for a landing zone upon a successful landing while the score and fuel are being updated.
4. Increased the moon’s "gravity" and "thrust" of the LEM engine. This does seem to add more tension to the game and increase the skill required to successfully land. At the very least it changes the mechanics enough throw someone off who has been playing at different settings (like me ;-)  Definitely a candidate for having optional easy and hard modes of play.