Adding simple particles

Reference implementation by Daniel Shiffman at processing.org
https://processing.org/examples/simpleparticlesystem.html

Particles are spawned at the mouse position.

examples/shapes/shapes_simple_particles.c

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+/*******************************************************************************************
+*
+*   raylib [shapes] example - simple particles
+*
+*   Example complexity rating: [★☆☆☆] 1/4
+*
+*   Example originally created with raylib 5.6, last time updated with raylib 5.6
+*
+*   Example contributed by Aanjishnu Bhattacharyya (@nimcompoo-04)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2025 Aanjishnu Bhattacharyya (@nimcompoo-04)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+#include "raymath.h"        // For Vector2Scale and Vector2Add
+
+#include <stdio.h>
+#include <math.h>
+
+#define MAX_PARTICLES 512
+
+//----------------------------------------------------------------------------------
+// Types and Structures Definition
+//----------------------------------------------------------------------------------
+typedef struct Particle {
+    Vector2 position;       // Position of the particle on screen
+    Vector2 velocity;       // Velocity of the particle
+    float radius;           // Radius of the circular particle
+    Color color;            // Color of the particle
+    float life_time;        // Total time particle will be alive
+    float elapsed_time;     // Time the particle has been alive
+} Particle;
+
+
+//----------------------------------------------------------------------------------
+// Program main entry point
+//----------------------------------------------------------------------------------
+int main(void)
+{
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    const float gravity = 150;                 // How fast the particles fall
+    const float emission_rate = 80;            // Number of particles created each second
+
+    float elapsed_time = 0;                    // time passed from last particle emission
+    float emission_time = 1. / emission_rate;  // time passed between each particle emitted
+
+    Particle particles[MAX_PARTICLES] = {0};   // Particles that emitter has emitted
+    int particle_count = 0;                    // Number of particles emmitted yet
+
+
+    InitWindow(screenWidth, screenHeight, "raylib [shapes] example - simple particles");
+
+    SetTargetFPS(60);               // Set our game to run at 60 frames-per-second
+
+    //--------------------------------------------------------------------------------------
+    // Main game loop
+    while (!WindowShouldClose())    // Detect window close button or ESC key
+    {
+        float dt = GetFrameTime();
+
+        //--------------------------------------------------------------------------------------
+        // Update
+
+        // Updating states of all the particles
+        for(int i = 0; i < particle_count; i++)
+        {
+            // Updating time that the particle has been alive for
+            particles[i].elapsed_time += dt;
+
+            // Checking if the time they are alive is greater than their supposed lifetime
+            if(particles[i].elapsed_time > particles[i].life_time)
+            {
+                // Swapping out the last particle with the particle to be removed
+                Particle temp = particles[i];
+                particles[i] = particles[particle_count - 1];
+                particles[particle_count - 1] = temp;
+
+                // Removing the last particle which is now the
+                particle_count--;
+            }
+
+            // If the particle is alive we update the particle
+            else
+            {
+                // Creating a copy for clarity
+                Particle *this = &particles[i];
+
+                // Adding a small vertical velocity
+                this->velocity.y += gravity * dt;
+                this->position = Vector2Add(this->position, Vector2Scale(this->velocity, dt));
+
+                // We also reduce the opacity of the color each frame
+                this->color.a = 255 * (1 - this->elapsed_time / this->life_time);
+            }
+        }
+
+        // We check if enough time has passed, if so we add new particle
+        if(elapsed_time >= emission_time && particle_count < MAX_PARTICLES)
+        {
+            float degrees = GetRandomValue(180, 360);   // a random angle towards the top
+            float angle = degrees / 180 * PI;           // converting to radians
+            float vel = GetRandomValue(0, 1000)/10.;    // a random magnitude for the velocity, value between [0, 2]
+
+            Particle new = {
+                .position = GetMousePosition(),     // Generating new particles at the location of the mouse
+                .velocity = {vel * cos(angle),
+                             vel * sin(angle)},     // Throwing the particle at a random direction
+                .radius = 6,                       // Radius of the particle generated
+                .color = WHITE,
+                .life_time = 4,                     // the particle will be alive for 3 seconds
+                .elapsed_time = 0                   // the particle just spawned
+            };
+
+            particles[particle_count] = new;      // adding the particle to the list
+            particle_count++;
+
+            elapsed_time = 0;       // Resetting the timer
+        }
+        elapsed_time += dt;         // incrementing the timer
+        //----------------------------------------------------------------------------------
+
+        //----------------------------------------------------------------------------------
+        // Draw
+        BeginDrawing();
+            ClearBackground(BLACK);
+
+            // Drawing all the particles
+            for(int i = 0; i < particle_count; i++)
+            {
+                DrawCircleV(particles[i].position, particles[i].radius, particles[i].color);
+            }
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    CloseWindow();        // Close window and OpenGL context
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}