Adds undo feature

README.md

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+# mcfreecell
+
+`mcfreecell` on `leg-py1.5.2` is a terminal-native FreeCell build aimed at old Python and old curses environments.
+
+This branch keeps the implementation within a Python-1.5.2-friendly subset and favors compatibility over modern terminal features.
+
+## Features
+
+- FreeCell rules with 8 tableau columns, 4 free cells, and 4 foundations
+- keyboard-driven curses interface
+- visual stack selection mode
+- single-step undo for completed moves
+- lightweight `?` hint system
+- ASCII-only suit tags for old terminals and fonts
+- compatibility fallbacks for weak or incomplete curses implementations
+
+## Controls
+
+- `Arrow keys` / `h j k l` - move cursor
+- `v` - enter or exit tableau selection mode
+- `y` - pick up selected card or stack
+- `p` - drop held card or stack
+- `u` - undo the last completed move
+- `Enter` / `Space` - alternate pick up / drop
+- `?` - show a suggested move
+- `f` - quick move selected card to a free cell
+- `d` - quick move selected card to foundation
+- `Esc` - cancel held move
+- `q` - quit
+
+## Suits
+
+- Debian (`Deb`)
+- Red Hat (`RHt`)
+- Solaris (`Sol`)
+- HP-UX (`HPx`)
+
+These are split into the two FreeCell color groups as:
+
+- red group: Debian, Red Hat
+- black-equivalent group: Solaris, HP-UX
+
+On older terminals, the non-red group may render as blue, cyan, or plain monochrome depending on curses support.
+
+## Running
+
+Run with whatever Python interpreter is available on the target machine:
+
+```sh
+python linux-freecell.py
+```
+
+## Terminal Notes
+
+Terminal and curses behavior can vary significantly on older systems.
+
+- `xterm` generally gives the most reliable screen redraw behavior for this branch.
+- Older `konsole` builds, including KDE 2.x-era versions, may show redraw artifacts or ghosting until the screen is resized.
+- The game includes several repaint fallbacks for weaker curses implementations, but some VT100-style emulator quirks are still terminal-specific.
+
+## Status
+
+This branch is intended as a playable legacy-friendly FreeCell build for old Unix-like systems and older Python environments.