{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import matplotlib.pyplot as plt\n",
    "from matplotlib import cm\n",
    "import numpy as np\n",
    "from celluloid import Camera\n",
    "\n",
    "i=0\n",
    "t=0\n",
    "all_clear = 0\n",
    "\n",
    "\n",
    "\n",
    "#set up the evironment\n",
    "\n",
    "#box\n",
    "x_left = -4\n",
    "x_right = 4\n",
    "y_bottom = -4\n",
    "y_top = 4\n",
    "wall_center = 0\n",
    "door_width = 3\n",
    "\n",
    "\n",
    "ball_count = 40\n",
    "\n",
    "# random starting speed and direction for each ball\n",
    "speed = np.random.uniform(low=0.1, high=1, size=(ball_count,2))\n",
    "speed /=10\n",
    "\n",
    "for i in range(0,ball_count):    \n",
    "    k = (-1)**np.random.randint(2)    \n",
    "    if k != 0 :    \n",
    "        speed[i][0] *= k \n",
    "        \n",
    "for i in range(1,ball_count):   \n",
    "    k = (-1)**np.random.randint(2)   \n",
    "    if k != 0 :    \n",
    "        speed[i][1] *= k \n",
    "\n",
    "        \n",
    "\n",
    "\n",
    "# ball coord. array\n",
    "ball = np.random.uniform(low=x_left, high=x_right, size=(ball_count,2))\n",
    "\n",
    "camera = Camera(plt.figure())\n",
    "\n",
    "\n",
    "\n",
    "while all_clear !=1 :\n",
    "    \n",
    "    # draw wall\n",
    "    plt.plot([0,0], [y_bottom,0 - door_width/2], lw=2 , color = 'black')\n",
    "    plt.plot([0,0], [door_width/2, y_top], lw=2 , color = 'black')\n",
    "    plt.plot([0,0], [-door_width/2, door_width/2], lw=2 , color = 'cyan')\n",
    "\n",
    "   \n",
    "    for j in range(0, ball_count):\n",
    "       \n",
    "        b_x = ball[j][0]\n",
    "        b_y = ball[j][1]\n",
    "        s_x = speed[j][0]\n",
    "        s_y = speed[j][1]     \n",
    "        \n",
    "        # x bounce logic\n",
    "        if b_x <= x_left or b_x >= x_right:\n",
    "            \n",
    "            speed[j][0] *= -1\n",
    "            \n",
    "        if x_left < b_x < wall_center:\n",
    "            \n",
    "            if b_x >= wall_center - 0.1 and s_x > 0 :\n",
    "                         \n",
    "                if j >= ball_count // 2 or b_y >= door_width/2 or b_y <= - door_width/2:\n",
    "                             \n",
    "                    speed[j][0] *= -1         \n",
    "                    \n",
    "                else:\n",
    "                    plt.plot([0,0], [-door_width/2, door_width/2], lw=2 , color = 'purple')\n",
    "            \n",
    "            \n",
    "        elif wall_center < b_x < x_right:\n",
    "            \n",
    "            if b_x <= wall_center + 0.1 and s_x < 0 :\n",
    "                             \n",
    "                if j < ball_count // 2 or b_y >= door_width/2 or b_y <= - door_width/2:\n",
    "                                        \n",
    "                    speed[j][0] *= -1\n",
    "                    \n",
    "                else:\n",
    "                    plt.plot([0,0], [-door_width/2, door_width/2], lw=2 , color = 'yellow')\n",
    "       \n",
    "        # y bounce logic\n",
    "        if b_y >= y_top or b_y <= y_bottom:\n",
    "            \n",
    "            speed[j][1] *= -1\n",
    "       \n",
    "        \n",
    "        \n",
    "       \n",
    "        # move ball  \n",
    "        ball[j][0] += speed[j][0]\n",
    "        ball[j][1] += speed[j][1]\n",
    "        \n",
    "     \n",
    "  \n",
    "    # differentiate red and blue\n",
    "    for j in range(0, ball_count // 2 - 1 ):\n",
    "        \n",
    "        plt.scatter(ball[j][0],ball[j][1], c='red', s=40)   \n",
    "    \n",
    "    for j in range(ball_count // 2, ball_count):\n",
    "\n",
    "        plt.scatter(ball[j][0],ball[j][1], c ='blue', s=40)\n",
    "    \n",
    "    plt.xlim(x_left, x_right)    \n",
    "    plt.ylim(y_bottom, y_top)\n",
    "    \n",
    "    camera.snap()\n",
    "    \n",
    "    # frame count\n",
    "    if t == 1000:\n",
    "        \n",
    "        all_clear = 1\n",
    "        \n",
    "    t += 1\n",
    "    \n",
    "anim = camera.animate(interval = 30, blit=True)\n",
    "\n",
    "anim.save('Maxwell_s_Demon.mp4')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-1"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "ball_count % 2 - 1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "ename": "SyntaxError",
     "evalue": "invalid syntax (<ipython-input-17-dd9916b08498>, line 1)",
     "output_type": "error",
     "traceback": [
      "\u001b[0;36m  File \u001b[0;32m\"<ipython-input-17-dd9916b08498>\"\u001b[0;36m, line \u001b[0;32m1\u001b[0m\n\u001b[0;31m    ball[*][0]<0\u001b[0m\n\u001b[0m         ^\u001b[0m\n\u001b[0;31mSyntaxError\u001b[0m\u001b[0;31m:\u001b[0m invalid syntax\n"
     ]
    }
   ],
   "source": [
    "ball[][0]<0\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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