Games: Pong, Snake and Tetris as seeded state machines, and a tune

The rules of the three Games (issue #101), with no screen and no keyboard in them: time and keys go in, the new state and what happened come out, and a seed decides the dice. With a player for a tune a note at a time, and Korobeiniki's notes. Host-tested. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk
2026-10-13 22:59:05 +02:00
parent 5c660d866d
commit 68d50b320f
9 changed files with 1417 additions and 0 deletions
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+#pragma once
+
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <deque>
+
+#include "game_rng.h"
+
+namespace roro::games {
+
+// Snake (issue #101): a field of 38 x 19 cells, the walls and its own body kill it, and it goes
+// faster as it eats. Time comes in from outside, in milliseconds.
+class Snake {
+   public:
+    static constexpr int kCols = 38, kRows = 19;
+    static constexpr uint32_t kSlowestMs = 150, kFastestMs = 60, kFasterMs = 5;
+    static constexpr int kFoodsAStep = 3;  // it gets faster every so many
+
+    enum class Dir : uint8_t { Up, Right, Down, Left };
+    enum Event : uint8_t { Moved = 1, Ate = 2, Died = 4 };
+    struct Cell {
+        int8_t col, row;
+        bool operator==(const Cell& o) const { return col == o.col && row == o.row; }
+    };
+
+    explicit Snake(uint32_t seed) : rng_(seed) { start(); }
+    void start();
+    // A turn asked for; it is taken at the next move. Two are remembered, so a quick corner (up,
+    // then left) works; turning back on itself is not a turn.
+    void turn(Dir dir);
+    uint8_t step(uint32_t ms);
+
+    bool alive() const { return alive_; }
+    int score() const { return score_; }  // foods eaten
+    const std::deque<Cell>& body() const { return body_; }  // the head first
+    Cell food() const { return food_; }
+    Dir heading() const { return dir_; }
+    uint32_t intervalMs() const;  // between two moves, now
+    // For the tests: the food put where one wants it.
+    void putFood(Cell at) { food_ = at; }
+
+   private:
+    bool taken(Cell c) const { return taken_[static_cast<size_t>(c.row * kCols + c.col)]; }
+    void mark(Cell c, bool on) { taken_[static_cast<size_t>(c.row * kCols + c.col)] = on; }
+    void placeFood();
+    uint8_t move();
+
+    Rng rng_;
+    std::deque<Cell> body_;
+    std::array<bool, kCols * kRows> taken_{};
+    Cell food_{0, 0};
+    Dir dir_ = Dir::Right;
+    Dir turns_[2] = {Dir::Right, Dir::Right};
+    int turnCount_ = 0, score_ = 0;
+    uint32_t sinceMs_ = 0;
+    bool alive_ = true;
+};
+
+}  // namespace roro::games