some new stuff.

idk its all pretty fun! some C++ too!

simulations/pendulum/main.py

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+import pygame
+import math
+
+# Initialize Pygame
+pygame.init()
+
+# Screen setup
+WIDTH, HEIGHT = 800, 600
+screen = pygame.display.set_mode((WIDTH, HEIGHT))
+pygame.display.set_caption("Interactive Adjustable Pendulum")
+
+# Colors
+BLACK = (0, 0, 0)
+WHITE = (255, 255, 255)
+RED = (200, 50, 50)
+
+# Clock for FPS
+clock = pygame.time.Clock()
+FPS = 60
+
+# Pendulum properties
+origin = (WIDTH // 2, 100)
+length = 300
+angle = math.pi / 4
+angular_velocity = 0
+angular_acceleration = 0
+gravity = 0.8
+dragging = False
+drag_padding = 30  # extra radius for easier dragging
+
+def get_bob_position(angle):
+    x = origin[0] + length * math.sin(angle)
+    y = origin[1] + length * math.cos(angle)
+    return int(x), int(y)
+
+bob_pos = get_bob_position(angle)
+
+running = True
+while running:
+    for event in pygame.event.get():
+        if event.type == pygame.QUIT:
+            running = False
+        # Start dragging
+        elif event.type == pygame.MOUSEBUTTONDOWN:
+            mx, my = event.pos
+            if math.hypot(mx - bob_pos[0], my - bob_pos[1]) < 20 + drag_padding:
+                dragging = True
+        # Stop dragging
+        elif event.type == pygame.MOUSEBUTTONUP:
+            dragging = False
+
+    # Keyboard controls
+    keys = pygame.key.get_pressed()
+    if keys[pygame.K_UP]:
+        length += 1  # increase pendulum length
+    if keys[pygame.K_DOWN]:
+        length = max(50, length - 1)  # decrease length, min 50
+    if keys[pygame.K_RIGHT]:
+        gravity += 0.01
+    if keys[pygame.K_LEFT]:
+        gravity = max(0.1, gravity - 0.01)
+
+    if dragging:
+        mx, my = pygame.mouse.get_pos()
+        dx = mx - origin[0]
+        dy = my - origin[1]
+        angle = math.atan2(dx, dy)
+        angular_velocity = 0
+        bob_pos = get_bob_position(angle)
+    else:
+        # Physics
+        angular_acceleration = (-gravity / length) * math.sin(angle)
+        angular_velocity += angular_acceleration
+        angle += angular_velocity
+        angular_velocity *= 0.99  # damping
+        bob_pos = get_bob_position(angle)
+
+    # Drawing
+    screen.fill(BLACK)
+    pygame.draw.line(screen, WHITE, origin, bob_pos, 3)
+    pygame.draw.circle(screen, RED, bob_pos, 20)
+    pygame.draw.circle(screen, WHITE, origin, 5)
+
+    # Display info
+    font = pygame.font.SysFont(None, 24)
+    info = font.render(f"Length: {int(length)}  Gravity: {gravity:.2f}", True, WHITE)
+    screen.blit(info, (10, 10))
+
+    pygame.display.flip()
+    clock.tick(FPS)
+
+pygame.quit()