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Introduction to Python, the Programming Language
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diff --git a/posts/2024/3_basic_Python/learn-some-python-with-retro-computer-battle-games.md b/posts/2024/3_basic_Python/learn-some-python-with-retro-computer-battle-games.md
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+# Learn Some Python with Retro Computer Battle Games
+## About
+我们将会用一些简单的远古电脑小游戏作为 Python 入门的练习.
+这些小游戏来自 Computer Battle Games (For ZX Spectrum,
+ZX81, TRS-80, APPLE, VIC & PET), 是一本由 [Usborne](https://usborne.com/) 出版社,
+出版于 1982 年的适用于儿童的计算机普及读物.
+
+你可以在 [Intenet Archive](https://archive.org/details/computer-battlegames) 网站上游览或者下载它,
+或者你也可以在 [Usborne 的存档网站](https://usborne.com/row/books/computer-and-coding-books)上找到同一系列的书籍.
+不过本部分并不会完全按照原书的内容进行介绍 (毕竟原书是
+BASIC 语言, 而非 Python). 不过你可以将其作为课外消遣读物,
+不过毕竟是儿童计算机读物, 对小学生来说可能有些幼稚,
+但是对大学生来说估计刚刚好.
+
+### Pre-requirements
+你应该对 Python 有稍微的了解,
+这里推荐阅读 [这篇文章中的 Pythonin 20 min](./trivial-python-introduction.md) 一节,
+小小花个 20 分钟入个门.
+
+### Typo
+为了方便, 对于原文中比较中二的背景设定我直接使用的是 OCR 识别,
+所以如果有 typo, 请提交 issue 来修改.
+
+### TOC
++ [Robot Missile](#robot-missile)
++ [The Vital Message](the-vital-message)
++ [Shootout](shootout)
+
+## Robot Missile
+> The year is 2582 and the people of Earth are in the midst of battle
+> against the Robots. A lethal Robot Missile has just landed and
+> everyone is depending on you to find the secret code which unlocks
+> its defuse mechanism. If you fail, the entire Earth Command
+> Headquarters will be blown up.
+>
+> Your computer knows what the code letter is. You must type in your
+> guess and it will tell you whether the code letter is earlier or
+> later in the alphabet.
+>
+> You have four chances to find the correct letter before the missile
+> blows up.
+
+请参考 [robot-missile.py](./src/computer-battle-game/robot-missile.py).
+
+<details>
+<summary>简单写一个小游戏外挂</summary>
+<div markdown="1">
+
+我们发现这个小游戏完全可以用[二分法](https://zh.wikipedia.org/zh-cn/二分法_(數學)) 来解决,
+因为 `math.log(26) = 3.25 < 4`.
+
+那么我们完全可以写一个简单的二分搜索小外挂:
+
+```python
+def guess_number():
+    # 这里用到了一个多赋值
+    left, right = 'A', 'Z'
+
+    # 这里 // 是整除
+    guess = chr((ord(left) + ord(right)) // 2)
+
+    while True:
+        if success_p(guess):
+            return guess
+        elif later_p(guess):
+            left, right = guess, right
+            guess = chr((ord(left) + ord(right)) // 2)
+        else:
+            left, right = left, right
+            guess = chr((ord(left) + ord(right)) // 2)
+
+        if left == right:
+            return None
+```
+
+我们在课上将会介绍如何编写 `success_p` 以及 `later_p` 的函数,
+来和外部的程序进行 IO 交互并且自动化输入命令. (这是一个查文档的例子)
+
+</div>
+</details>
+
+## The Vital Message
+> You are a laser communications operator. Your job is to intercept
+> robot messages and relay them to Command HQ. A vital code message
+> is expected. If you relay it correctly, the Robot attack will be
+> crushed.
+>
+> This game tests your skill at remembering a group of letters which
+> you see for only a very short time. The computer will ask you for a
+> difficulty from 4 to 10. When you have typed in your answer, letters
+> will appear top left of your screen and disappear again fairly quickly.
+> Memorize them and then type them into the computer and see if you
+> were right.
+
+请参考 [vital-message.py](./src/computer-battle-game/vital-message.py).
+
+<details>
+<summary>一些说明</summary>
+<div markdown="1">
+
+这个游戏其实原理非常简单, 所以我们并不会对这个游戏的逻辑进行解释.
+在这里我们将会换一些考查视角: 如果用户不按照我们想要的方式输入,
+那么会发送什么? 如果用户的设备不是 Unix-like, 那么代码会发生什么?
+
+即, 如何处理用户输入以及如何处理多端移植.
+
+</div>
+</details>
+
+## Shootout
+> You are standing back to back. You take 10 paces, turn and reach
+> for your gun. How quick are you? Can you shoot first?
+>
+> Your computer prints the numbers 1 to 10 to represent the 10 paces,
+> pauses and then prints HE DRAWS...
+>
+> You must be ready to press a key (any one will do) the instant these
+> words come of the screen. If you are quick enough, you will win. Don't
+> press a key before HE DRAWS comes up or you automatically lose.
+
+(coming soon... or we could write it on class)
+
+## Desert Tank Battle
+> The last major stronghold of Robot forces outside the U.R.S*
+> is hidden in ancient castle ruins in the middle of the desert.
+> A fleet of desert hovertanks has beensent to destroy it and you
+> are the commander. Your tank controls the five remaining missiles.
+>
+> You must assess carefully the direction and elevation before you
+> launch each one. Your computer will ask you for a direction angle
+> between -90° (extremeleft) and +90° (extreme right) and an elevation
+> angle between 0° (along the ground) and 90° (straight up in the air).
+> The elevation determines the distance the missile will travel.
+>
+> Is your aim good enough to destroy the robot stronghold?
+
+老实说, 这几个代码其实都是差不多的原理, 看那么多类似的代码其实更多的是提高熟练度.
+
+但是这是为了作为课程练习, 所以我们需要一些新的东西来不让我们像是在原地踏步.
+所以在这个例子中, 我们做的事情是一个代码的 "转写" 工作. 我们会拿到一个
+BASIC 代码 (其实不管是什么代码都行), 然后我们需要将其变成一个 Python 代码.
+
+<details>
+<summary>BASIC 代码</summary>
+<div markdown="1">
+
+```basic
+10 PRINT "DESERT TANK BATTLE"
+20 LET T=INT(RND*181)-90
+30 LET D=RND
+
+40 FOR G=1 TO 5
+50 PRINT "DIRECTION (-90 TO 90) ?"
+60 INPUT T1
+70 PRINT "ELEVATION (0 TO 90) ?"
+80 INPUT B
+90 LET D1=SIN(2*(B/180*3.1416))
+
+100 IF ABS(T-T1)<2 AND ABS(D-D1)<.05 THEN GOTO 220
+110 PRINT "MISSILE LANDED ";
+120 IF T1<T THEN PRINT "TO THE LEFT ";
+130 IF T1>T THEN PRINT "TO THE RIGHT ";
+140 IF ABS(D1-D)>.05 AND T1<>T THEN PRINT "AND ";
+150 IF D-D1>.05 THEN PRINT "NOT FAR ENOUGH";
+160 IF D1-D>.05 THEN PRINT "TOO FAR";
+170 PRINT
+
+180 NEXT G
+
+190 PRINT "DISASTER - YOU FAILED:
+200 PRINT "RETREAT IN DISGRACE"
+210 STOP
+
+220 PRINT "*KABOOOMMM*"
+230 PRINT "YOU'VE DONE IT"
+240 STOP
+```
+
+评价: 其实完全和前面的 [Robot Missile](#robot-missile) 是差不多的逻辑,
+所以你也可以尝试用 Robot Missile 中写外挂的技术来进行一个外挂的编.
+
+</div>
+</details>
+
+请参考 [desert-tank-battle.py](./src/computer-battle-game/desert-tank-battle.py).
+
+这是一个简单的转写例子, 你可能需要随时查询 BASIC 的用法,
+以及搞到一台能跑 BASIC 的模拟器.
+
+这里推荐使用 APPLE II 的 BASIC ([applesoft 链接](https://paleotronic.com/applesoft/), 或是 [jsbasic](https://www.calormen.com/jsbasic/)).
+
+当然, 有兴趣的同学可以尝试编写一个 BASIC 的解释器, 如果将来有时间,
+我们可以考虑用这个 BASIC 来作为一个简单虚拟机的练习.
+
+## Iceberg
+> 
diff --git a/posts/2024/3_basic_Python/src/computer-battle-game/desert-tank-battle.py b/posts/2024/3_basic_Python/src/computer-battle-game/desert-tank-battle.py
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+# 这里和之前 import 整个模块名称不一样,
+# 在这里我们只导入模块的一个函数,
+# 并让我们可以直接用 `randint` 和 `random' 的方式去调用
+from random import randint, random
+
+def desert_tank_battle_game():
+    print("DESERT TANK BATTLE")
+
+    # 20 LET T=INT(RND*181)-90
+    # 30 LET D=RND
+    flag_degree = randint(90, 180)
+    flag_distance = random()
+
+    # TODO: in class
+    # + we will use this as an example of
+    #   converting any language code logic to python,
+    #   which is useful when you're doing reversing
+
+    # 40 FOR G=1 TO 5
+    try_times = 1
+    while try_times <= 5:
+        # 60 INPUT T1
+        # 80 INPUT B
+        try_degree   = int(input("DIRECTION (-90 TO 90) ?"))
+        try_distance = int(input("ELEVATION (0 TO 90) ?"))
+
+        # ... more ...
+
+if __name__ == "__main__":
+    desert_tank_battle_game()
diff --git a/posts/2024/3_basic_Python/src/computer-battle-game/robot-missile.py b/posts/2024/3_basic_Python/src/computer-battle-game/robot-missile.py
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+import random
+
+def print_title():
+    # 在 Python 中, `print` 命令支持多个参量的输出, 并且可以用 `sep` 分隔.
+    # 请尝试不同的 `print` `sep` 参数并看看效果如何
+    print("Robot Missile",
+          "",
+          "Type the CORRECT CODE lettler (A-Z) to",
+          "defuse the missile. ",
+          "",
+          "You have 4 chance:",
+          sep="\n")
+
+def guess_loop():
+    # 在这里我们调用了三个函数:
+    # + `chr`: int -> char
+    # + `ord`: char -> int
+    # + `random.randint(a : int, b : int)`: 获得 `a`, `b` 之间的一个随机整数
+    # 请借助 LSP 或是你编辑器的自动文档来阅读它们的细致说明
+    flag = chr(random.randint(ord('A'), ord('Z')))
+
+    try_times  = 0
+    while try_times < 4:
+        # 在这里是一个简单的 IO 操作:
+        # `input`: 从 stdin 中读取一个字符串
+        char = input("Try: ")[0]
+
+        # 这里是一个自增算符
+        try_times += 1
+
+        if char == flag:
+            print("TICK...FZZZZ...CLICK...",
+                  "YOU DID IT",
+                  sep="\n")
+            return True
+        elif char < flag:
+            print("LATER")
+        else:
+            print("EARLIER")
+
+    print("BOOOOOOOOOOOMMM...",
+          "YOU BLEW IT.",
+          f"The correct code was '{flag}'. ",
+          sep="\n")
+    return False
+
+# TODO in class:
+# + add restart
+# + add quit control command
+if __name__ == "__main__":
+    print_title()
+    guess_loop()
diff --git a/posts/2024/3_basic_Python/src/computer-battle-game/vital-message.py b/posts/2024/3_basic_Python/src/computer-battle-game/vital-message.py
@@ -0,0 +1,64 @@
+import os
+import random
+import time
+
+def clear_screen():
+    """
+    Poor-man's clear screen.
+    """
+    os.system('clear')
+
+# 这里是我们第一次接触 Python 的 type-hint
+# 这是一种给变量静态类型提示的语法,
+# 有助于对我们调用函数的时候提供类型提示
+# 尽管这和 C 中的类型标记并不完全相同,
+# 因为你完全可以无视类型提示随便传值
+#
+# TODO: exercise
+# + how to make the game harder?
+def random_string(length : int) -> str:
+    """
+    Return a random string at length.
+    """
+    return "".join([chr(random.randint(ord('A'), ord('Z'))) for i in range(length)])
+
+def vital_message():
+    # 这里我们用到了字符串转义
+    # 在字符串中 `\` 表示对后面的字符进行 "转义",
+    # 即让后面跟着的字符不再是字面量字符,
+    # 而是具有一定意义的控制字符. 比如说:
+    # + `\n` 表示换行 (Newline)
+    print("Vital Message\n")
+
+    # 这里我们有一个新的函数 `int` (`__int__`)
+    # 表示将对象转换为 `int` (整形)
+    #
+    # TODO: in class
+    # + safety check?
+    # + assert `difficulty` between 4 and 10
+    difficulty = int(input("How Difficult? (4-10): "))
+    flag = random_string(difficulty)
+
+    clear_screen()
+    print(f"Send this message: '{flag}'")
+
+    # 这里用到了 `time.sleep` 来等待一段时间
+    #
+    # TODO: as exercise
+    # + how to set different time?
+    time.sleep(3)
+    clear_screen()
+
+    message = input("What is the message? Input: ")
+    if message == flag:
+        print("Message Correct",
+              "The WAR is over",
+              sep="\n")
+    else:
+        print("You got it wrong",
+              "You should have sent:",
+              flag,
+              sep="\n")
+
+if __name__ == "__main__":
+    vital_message()