Adventures in Unity: Making an object move one step at a time – Tetris-style

I hit a small mental block with Project X (codename for my RealGame™ that I am trying to build in Unity), so decided to try to do something a bit simpler first, and see how that goes, purely as a learning experience, getting used to Unity and its quirks.  I decided to make a Tetris clone.

At first I thought “Hey, Unity has a physics engine, Tetris blocks drop down, I can use the physics engine!” – but alas, no, that’s not the greatest idea, as you essentially need to switch off everything about the physics engine, except for gravity really, to make it work.   Too much work, and too much randomness that could creep in.   Especially if you’re using the 3D engine but presenting it in 2D, as I had intended initially.  I figured the final game could present the blocks in 3D as they drop down, maybe move the camera around a bit depending on which side of game grid the object is, etc.  So I am sticking to 3D for now.

Ah, but the reason you’re here, you want to make an object move on “step” at a time, like a tetris block moves, over time.  I just created a script for that, see it at my GitHub repo: StepObject.cs

Here’s how it works:

Here is just the beginning of the script, we make our four public variables available and initialise a couple of private variables.  Our Start() method merely checks that we have the required variables to be able start moving at startup, if so required, so if we have SecondsPerStep and a MoveDirection is set, we make the Moving private variable equal to whatever you chose in the Inspector for the StartMoving tickbox.

Here is the meat of the script, quite small actually, not very meaty at all.  In every Update, we increase the value of the Timer variable by Time.deltaTime.  We use the Timer variable to count how much time has passed since the last time the object moved.

Et voila.  Done.  Very simple actually.  To use this in a Tetris-like game, you would adjust the SecondsPerStep variable over time as the difficulty increases, lowering that value for each level gained.  You would probably start with a number of 2 seconds per step at level one.  If you create your game grid to be one unit per square, then your MoveDirection Vector would be equal to (0,-1,0).

Please give me feedback if you use this script, and let me know how things go.

Here’s the full script code:

 

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