初中级Lower intermediate在线实验室Online lab可打印Printable
贪吃蛇规划：最近的苹果为什么害了我？
Snake Planning: Why Did the Nearest Apple Trap Me?
一步合法，不等于下一步还有路。先比较距离，再模拟身体移动，检查出口和可达空间。
A legal move may leave no next move. Compare distance, simulate the moving body and inspect exits and reachable space.
苹果就在右边一格，为什么机器人反而应该先向上走？先画出吃完苹果以后的身体。
The apple is one square to the right. Why might a robot go up first? Draw its body after eating before deciding.
开始之前Before you start
模拟一次移动和吃食物后的身体，区分现在合法、下一步有出口、长远一定安全三种不同结论。
Simulate a move and growth, distinguishing legal now, having a next exit and guaranteed long-term safety.
读 A–E、1–5 坐标；会比较距离。理解头先移动，没吃时尾巴腾一格，吃到时尾巴保留。
Read coordinates A–E and 1–5, compare distances, and understand that the tail moves on a normal step but stays when eating.
一步一步试试看Try it step by step
- 先猜（5分钟）：看陷阱地图：头 B3，身体 A3、A4，朝右；苹果 C3、E1，墙 C2、D3、C4。先投票向右还是向上。Predict (5 min): head B3, body A3,A4, facing right; apples C3,E1; walls C2,D3,C4. Vote right versus up before running.
- 动手（10分钟）：在纸上先模拟向右吃 C3：尾巴不走，身体变长。把下一步四个方向逐个检查，不能倒退穿过自己的脖子。Try (10 min): move right onto C3 on paper. Eating keeps the tail and grows the body. Inspect all four next directions; reversing through the neck is forbidden.
- 观察（10分钟）：重置后向上到 B2，尾巴腾位，再数下一步出口。比较追最近苹果、排除立即碰撞、再看可达空间三种选择方法。Observe (10 min): reset, move up to B2, vacate the tail and count next exits. Compare nearest-food greed, immediate collision filtering and reachable-space planning.
- 挑战（10分钟）：换尾巴腾位地图，检查走进即将腾出的尾格何时合法。空间搜索把当前身体当障碍，只是保守快照；真正的未来还会变化。Challenge (10 min): use the vacating-tail board and check when entering that cell is legal. A space search freezing the current body is only a conservative snapshot; future occupancy changes.
一起算一个例子Work through one example
向右到 C3 吃苹果后，身体为 C3、B3、A3、A4。C2、D3、C4 是墙，B3 是脖子，所以下一步无路；当前一步本来合法。
After eating at C3, the body is C3,B3,A3,A4. Walls block C2,D3,C4 and the neck blocks B3, leaving no next move even though the first move was legal.
先想一想，再看答案Think first, then check
同一初始图向上到 B2 后，能走到哪些下一格？可达空间更大，是否就能保证永远活着？
After going up to B2, which next cells are legal? Does more reachable space guarantee survival forever?
查看参考答案Show the expected answer
向上后身体 B2、B3、A3，下一步可到 B1 或 A2；右 C2 是墙、下 B3 是脖子。向右吃苹果尾巴保留，下一步0个出口；向上没吃尾巴腾出，下一步2个。尾巴题：头 B2 朝上，身体 B3、A3、尾 A2，无食物在 A2 时左转到 A2 合法，因为尾巴同一步腾走。较大快照空间不保证长期安全，也没考虑所有未来吃食物与身体时序。
After up, the body is B2,B3,A3, and the next legal cells are B1 or A2; C2 is a wall and B3 the neck. Eating right keeps the tail and leaves zero exits; up vacates it and leaves two. Tail task: head B2 facing up, body B3,A3,tail A2; turning left into A2 is legal when it vacates on that non-eating step. A larger frozen-body region does not guarantee long-term safety or account for every future growth/timing effect.
这个实验说明了什么What this experiment shows
这是无对手、无穿越、无新食物刷新的单蛇课堂棋盘。空间法只在每个候选下一状态上做快照搜索，不是完整未来规划器；原多人游戏还有同步移动与其他模式。
This is a single-snake board without opponents, pass-through modes or food respawning. Space planning searches a snapshot after each candidate move, not the entire future; the original multiplayer game has simultaneous movement and additional modes.
学习单Worksheets
学习单用英文，可打印给孩子。教师指南随页面语言下载：当前为中文版。
Print the English worksheets for the children. The guide follows the page language: English is selected.
下载学习单（PDF）Download worksheets (PDF)教师指南（中文 PDF）Teacher guide (English PDF)
继续玩原项目Explore the original game
课堂实验可以离线使用。原项目有更多模式，可由老师带领继续探索。
The classroom lab works offline. The original project has more modes for teacher-led exploration.
视频与文章Videos and reading
- Lucas Academy: original game 原项目与玩法original project and game