Source: Day 4: Printing Department

Full solution for today (spoilers!).

Part 1

Given a grid of solid @ and empty cells ., count how many solid cells have less than 4 neighbors.

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Ludum Dare? That’s been a while!

I didn’t actually enter the game jam. Honestly, I wasn’t sure I was going to write anything. But I had a bit of an idea and spent a few hours only on Sunday hammering something out:

Yeah, I did another cellular automata thing 😄

It’s not at all complete, but the basic idea is:

• Generate a random level
• See it with multiple players (colonies of bugs)
• Each bug will send out waves of ‘shine’, expanding their territory
• Take over the map to win

It’s sort of got that?

I’m using Rust as I’ve been doing a lot recently.

The main libraries are:

• pixels for the rendering; it gives me direct access to a pixel buffer, which is my favorite
• winit for windowing; this did require the feature rwh_05 to be properly compatible with pixels, which took a minute to track down

Other than, that, it’s straight custom code which you can see in it’s entirety on my github.

• main.rs - creates the window and handles input
• world.rs - runs the simulation mostly in an update function; with generation in new

I think that perhaps the only really interesting bit about the code is how the ‘shine waves’ work. Basically, I have a grid of the state of each cell, but I also have a Vec that tracks ‘active’ pixels. Those are the only ones that can update–which both helps performance and makes the simulation appear the way it does.

Overall, a nice quick project. More than anything, it actually convinced me to try setting up something that can render pixel buffers on Rust. And with a (very minimal) GUI, too! Both things I’ve been meaning to learn.

I probably won’t do anything more with this code, but it’s got the seeds of something more interesting. Keep an eye out. 😄

Onward!

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Genuary!

Spend a month making one beautiful thing per day, given a bunch of prompts. A month late, but as they say, ’the second best time is now'.

Let’s do it!

5) Debug view

I like Boids. Here are some Boids with debug vectors drawn showing the three forces acting on them (red to stay away from one another, green to move in the same direction as their friends, blue to move towards the center of their friends).

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Source: Unstable Diffusion

Part 1

Implement a cellular automaton with the following rules:

• If you have no neighbors, don’t move (important, I forgot this one for a while)
• Otherwise:
  • Calculate a potential move:
    • If you have no neighbors to the north, move north
    • If not, check likewise for south, then west, than east
  • If no other agent is moving to the same space, move to your potential move
  • Otherwise, don’t move
• On each frame, rotate the order the directions are checked in (NSWE, SWEN, WENS, ENSW, NSWE, …)

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Source: Regolith Reservoir

Part 1

Given a series of walls as input, run a falling sand simulation until any new sand falls of the map. Count how many grains of sand we end up with.

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Source: Cathode-Ray Tube

Part 1

Implement a simple virtual machine with two instructions: nop which does nothing for 1 cycles and addx $n which adds $n to the X register (initial value 1) in two cycles. Calculate the sum of cycle * X for the cycles 20, 60, 100, 140, 180, 220.

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Source: Rope Bridge

Part 1

Simulate two connected links such that whenever the first link (head) moves, the tail moves to follow according to the following rules:

• If the tail is at the same location as head, don’t move
• If the tail is adjacent to the head (orthogonal or diagonal), don’t move
• If the tail is in the same row/column as the head, move one directly towards it orthogonally
• If the tail is in neither the same row nor column, move one towards diagonally

Count how many unique spaces are visited by the tail of the link.

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Source: Sea Cucumber

Part 1: Load a grid of empty cells (.), east movers (>), and south movers (v). Each step, move all east movers than all south movers (only if they can this iteration). Wrap east/west and north/south. How many steps does it take the movers to get stuck?

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Source: Trench Map

Part 1: Given a 9->1 cellular automota update function (take the pixel and 8 surrounding pixels as a 9-bit index into the function) and a binary image, apply the function twice and count the number of ’lit’ pixels. Assume that the canvas is infinite.

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Source: Dumbo Octopus

Part 1: Simulate a grid of numbers such that on each tick: advance all numbers by 1, any number that increases over 9 will ‘flash’ and add 1 to all neighbors (recursively, but each cell can only flash once) and then reset to 0. Count the number of flashes in the first 100 ticks.

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