Gamemaker Creative coding 001 : Crystal Growth

By Oliver @PixelChipCode

Description
This code creates a branching crystal growth effect in GameMaker. Clicking anywhere in the room starts a crystal that grows outward with occasional branching, creating a natural, organic visual effect. The crystals grow to a maximum length before stopping, and all growth is drawn on a persistent surface to maintain the visual effect. Pressing the "R" key will restart the room and clear the canvas.

Instructions for Setup:

Create two objects: obj_crystal and obj_spawner.
Attach the following code to their respective events.
Ensure the obj_spawner is placed in the room to manage the drawing surface and spawning.

//obj_crystal

//create event
growth_speed = .5; // Speed of growth (slower for more control)
branch_chance = 0.02; // Reduce the chance of branching to avoid excessive density
growth_length = irandom_range(12, 50); // Randomize length to make each branch different
current_length = 0;
direction = irandom(360); // Start with a random direction
turn_rate = random_range(-1, 1); // Slight random adjustment to make growth organic

//step event
// Grow the crystal if it hasn't reached its maximum length
if (current_length < growth_length) {
    // Gradually adjust the growth direction for more natural branching
    direction += random_range(-1, 1) + turn_rate;

    // Calculate growth direction
    var dx = lengthdir_x(growth_speed, direction);
    var dy = lengthdir_y(growth_speed, direction);
    var prev_x = x;
    var prev_y = y;

    x += dx;
    y += dy;
    current_length += growth_speed;

    // Draw the growth onto the surface
    if (surface_exists(global.crystal_surface)) {
        surface_set_target(global.crystal_surface);
        draw_set_color(c_white);
        draw_line_width(prev_x, prev_y, x, y, 1); // Use thin lines for a delicate look
        surface_reset_target();
    }

    // Occasionally create a new branch, but only if this branch is still growing
    if (random(1) < branch_chance && current_length > 10) { // Only branch after some initial growth
        var new_direction = direction + irandom_range(-30, 30); // Less variation for more controlled branching
        var new_crystal = instance_create_layer(x, y, "Instances", obj_crystal);
        new_crystal.direction = new_direction;
    }
}

//draw event
if (surface_exists(global.crystal_surface)) {
    draw_surface(global.crystal_surface, 0, 0);
}

// obj_spawner

//create event
// Create a surface for drawing the crystallization effect
global.crystal_surface = -1;

//step event
if(mouse_check_button(mb_left)){
// If the surface exists, start drawing on it
if (surface_exists(global.crystal_surface)) {
    surface_set_target(global.crystal_surface);

    // Set draw color for crystals
    draw_set_color(c_white);

    // Draw starting point
    draw_circle(mouse_x, mouse_y, 2, false);

    // Reset the surface target to the application (main screen)
    surface_reset_target();

    // Create an instance of obj_crystal at click point
    instance_create_layer(mouse_x, mouse_y, "Instances", obj_crystal);
}

}

if(keyboard_check_pressed(ord("R"))){
    room_restart();
}

//room start event
if (surface_exists(global.crystal_surface)) {
    surface_free(global.crystal_surface);
}
global.crystal_surface = surface_create(room_width, room_height);