Added a explosion in Particles

Particles/explosion.py

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+import random
+import math
+
+# the size of the screen
+WIDTH = 800
+HEIGHT = 600
+
+# how much a particle slows down by each second
+DRAG = 0.8 
+
+# the colour of each particle in R, G, B values
+PARTICLE_COLOR = 255, 230, 128
+
+# the time in seconds for which a particle is displayed
+MAX_AGE = 3
+
+# an array to hold the details of the explosion particles on the screen
+particles = []
+
+
+# This function creates a new explosion at the specified screen co-ordinates
+
+def explode(x, y, speed=300):
+
+    # these are new particles, so set their age to zero
+    age = 0     
+    
+    # generate 100 particles per explosion
+    for _ in range(100):
+    
+        # for each particle, generate a random angle and distance
+        angle = random.uniform (0, 2 * math.pi)
+        radius = random.uniform(0, 1) ** 0.5
+
+        # convert angle and distance from the explosion point into x and y velocity for the particle
+        vx = speed * radius * math.sin(angle)
+        vy = speed * radius * math.cos(angle)
+        
+        # add the particle's position, velocity and age to the array
+        particles.append((x, y, vx, vy, age))
+
+
+# This function redraws the screen by plotting each particle in the array
+
+def draw():
+
+    # clear the screen
+    screen.clear()
+    
+    # loop through all the particles in the array
+    for x, y, *_ in particles:
+        
+        # for each particle in the array, plot its position on the screen
+        screen.surface.set_at((int(x), int(y)), PARTICLE_COLOR)
+
+
+# This function updates the array of particles
+
+def update(dt):
+
+    # to update the particle array, create a new empty array
+    new_particles = []
+    
+    # loop through the existing particle array
+    for (x, y, vx, vy, age) in particles:
+    
+        # if a particle was created more than a certain time ago, it can be removed
+        if age + dt > MAX_AGE:
+            continue
+            
+        # update the particle's velocity - they slow down over time
+        drag = DRAG ** dt
+        vx *= drag
+        vy *= drag
+        
+        # update the particle's position according to its velocity
+        x += vx * dt
+        y += vy * dt
+        
+        # update the particle's age
+        age += dt
+        
+        # add the particle's new position, velocity and age to the new array
+        new_particles.append((x, y, vx, vy, age))
+        
+    # replace the current array with the new one
+    particles[:] = new_particles
+
+
+# This function creates an explosion at a random location on the screen
+
+def explode_random():
+
+    # select a random position on the screen
+    x = random.randrange(WIDTH)
+    y = random.randrange(HEIGHT)
+    
+    # call the explosion function for that position
+    explode(x, y)
+
+# call the random explosion function every 1.5 seconds
+clock.schedule_interval(explode_random, 1.5)