Astro Lander, a development summary

This project started as a simple remake of Lunar Lander.

Lunar Lander relies on a 2D gameplay with a simple use of physics and it exactly what I was looking for. I’m going to explore in this post how it finally evolved into something bigger, iteration after iteration.

A long list of improvements.

The initial change I wanted to implement on my remake was a multi directional scrolling, to offer a larger game area.
I built rapidly a minimalist level made of cubic blocks and started to write the physics and the controls of the Lunar Lander.
I found out that the game play could be accelerated, and then I made the ship to move faster. Rapidly, the challenge evolved from “land softly” to “navigate softly and avoid the walls”.
The goal of the game would be not only to reach a specific point, but also to collect a series of items scattered across each level.

The controls.

I started to focus on the controls of the ship. A Lunar Lander is basically about controlling the ship’s reactors versus the gravity and the inertia.
But I wanted to avoid the usual problems related to the rotation of the ship. If the player is in charge of both the thrust and the roll angle, a situation might occur where the ship is upside down and the thrust direction will sum up with the gravity, thus sending the ship even faster against the nearest wall.
To suppress the frustration inducted by such a control scheme, I wrote a simple routine that always controls the rotation of the ship. The player is free to move in any direction, the physics engine handles all the collision and physical responses, the ship can translation, rotate, bump into walls, but in the end it always remain properly oriented.
In my opinion, this is a good compromise for a physics-driver action game, where the physics engine makes the game looks real but doesn’t spoil the gameplay.

The code of this routine takes only a few lines of code :


//-------------------------
function AutoAlign(item)
//-------------------------
{
local _align, _speed

// Get the current orientation
local _rot_z = ItemGetRotation(item).z
// Get the angular speed (if the ship is rotating)
local _ang_v_z = ItemGetAngularVelocity(item).z

// Magic factors applied using an empirical approach …
_align = Clamp(Abs(RadianToDegree(_rot_z)) / 180.0,0.0,1.0)
_align *= 250.0

// … that defines the strength of the torque (angular force),
// applied on the ship to stabilize it
_speed = ItemGetLinearVelocity(item).Len()
_speed = RangeAdjust(_speed, 0.25, 0.5, 0.0, 1.0)
_speed = Clamp(_speed, 0.0, 1.0)
_align *= _speed

// Applies the torque
ItemApplyTorque(item, Vector(0,0,-_rot_z – _ang_v_z).Scale(_align * ItemGetMass(item)))
}

One of my friends who works in the game industry always told me that I needed to refine the controls before doing anything else on the game. During my past attempts at making a game, I disregarded this advice, and started with the level design. I eventually understood that Romain was right.

To bring the ship in motion, the player will only need to trigger the 2 side thrusters by touching the 2 halves of the screen. Such a basic control is perfectly suitable for smartphones and tablets, allowing you to concentrate on the game without having to constantly check that your fingers are properly positioned on the screen.
With the help of Emmanuel, I was finally able to tweak the core routine that drives the ship and defines the way lateral forces are applied to it. It ended up with the exact kind of behavior I was looking for, so the level design could start, at last!

The Level design

As I knew I couldn’t spend too much time on the graphics, I headed for the simplest method I could think of to build the levels : “lego bricks”. This technique, based on blocks, presented two benefits to me :

  • it is cheap in terms of time investment, because you only need to prepare a few blocks and you’re free to work with the GameStart editor. I didn’t have to constantly exchange back-and-forth between 3dsMax and GameStart.
  • it let’s the door open to a future extension that brings a lot of value to a game : a level editor that the players can work with to assemble new levels from scratch.

It has drawbacks too, of course. It’s a bit heavier for the engine to handle a large list of split blocks, and the overall visual aspect tends to be less realistic.

What’s next ?

Now that the game is almost done, with a series of 24 different levels, all we need is to polish the final builds both for iOS and Android platforms. As soon as the game is released, I’ll be able to focus on the next big implementation : the level editor.

In the meantime, you may enjoy the gameplay video below :

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