XLander is a lunar landing simulation for X. It features an "out-the-window" scrolling 3-d display.
As you play the game, you will see the landing craft on the screen. The 3-d view follows the craft around, lagging behind slightly, which gives a good illusion of motion.
The lander is equipped with five thrusters; four directional thrusters which control lateral motion, and one retroactive thruster which fires downwards to produce upward momentum. Each thruster is activated by pressing and holding a particular key. By default, the space bar fires the retroactive thruster, and the 8, 2, 4 and 6 keypad keys fire the front, rear, left and right directional thrusters, respectively. The control keys can be re-mapped using the -control option described below. You can also use the keyboard arrow keys to fire directional thrusters if you like.
Each thruster uses up a particular amount of fuel. The retro thruster consumes more fuel than the directional thrusters, since it produces more thrust to combat the force of gravity. Fuel is indicated on the control panel. Once it's gone, you can no longer thrust.
At the start of the game, your landing craft will be free-falling toward the surface. The goal is to land the craft on the landing pad with as little vertical and lateral motion as possible. The landing pad is visible as a square on the ground with a flag planted at one corner. The shadow of the craft is projected on the ground, allowing you to see how high it is and where it will land.
In order to land, you must be going slowly enough in both the vertical and lateral directions. Although you can land anywhere on the surface, you must land on the landing pad to get points. After each successful landing, the program gives you a score based on your vertical and lateral speeds, refills your fuel tank, and restarts the simulation at a higher difficulty level (by increasing the force of gravity). After you crash, the game shows your final score and then allows you to either start over or quit.
The lunar lander is equipped with a number of gauges and indicators which tell you its status. At the left of the gauge panel is a circular heading indicator which tells you the lateral direction of the craft. Next to this is a vertical velocity gauge, which tells you your rate of ascent or descent; after this comes a fuel gauge, followed by a radar screen which tells you your position relative to the landing pad.
Collision detection needs (a lot of) work. Suggestions, anyone?
Since we're not physicists or mathematicians, we don't claim that this is a completely accurate simulation. So, have fun with it but don't take it too seriously!
Paul Riddle (paulr@umbc3.umbc.edu)
Mike Friedman (mikef@umbc3.umbc.edu)