Games App: Pong, Snake and Tetris

A new App (issue #101) that shows its three Games as icons, as the
Launcher shows Apps, and plays the one chosen. A Game left in the middle
is found again paused; one being played keeps the screen lit. Tetris
plays Korobeiniki on a speaker channel of its own, faster with each
level: 0 switches it, 8 and 9 set its volume, both remembered. The drop
is on 1, away from the arrows. The best of each Game is kept.

Played on the device. The speeds are as tuned there.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

README.md

@@ -16,6 +16,7 @@ What it does today:
 - **Shell:** the firmware's commands on the device itself, with completion, including `ping`, `nslookup`, `port`, `traceroute`, `tls` and `ifconfig`.
 - **System:** load, tasks, memory, network, battery, live.
 - **SSH:** a terminal on another machine, with a password or the device's own key.
+- **Games:** Pong, Snake and Tetris.
 - **VPN:** a WireGuard tunnel.
 - **Everywhere:** Fn+h lists the keys of the screen you are on; Fn+p takes a screenshot.
 - **Updates:** signed, from the project's server, the card or a PC, with a rollback if the new firmware fails.
@@ -187,6 +188,12 @@ The SSH App (docs/milestones/N1.md, issue #2) is a terminal on another machine:
 
 The terminal (`lib/term`, host-tested) understands what a shell, `less`, `top`, `nano` and `vim` send: the cursor, erasing, sixteen colours, scroll regions, the alternate screen; no mouse. Five text sizes with Ctrl and + or -, from 60 x 20 to 26 x 8, told to the far end; 100 lines of scrollback with Alt and up or down. The backtick key sends Esc. **Leaving the App doesn't end the session:** `SSH` shows in the Status Bar and the App finds it again. It costs 292 KB of flash (109 KB of it one table, for signing with the device's key) and about 50 KB of memory while a session is open, so it isn't started under 75 KB free and IRC doesn't connect while one is open.
 
+## Games
+
+The Games App (issue #101) holds three Games, shown as a row of icons like Apps in the Launcher: Pong against the device (first to 7; the device's paddle has a top speed, so it can be beaten), Snake (38 x 19, the walls kill) and Tetris (10 x 20, the 7-bag, the next piece shown, a turn that shifts away from a wall, soft and hard drop). Each is a state machine in `lib/games`, host-tested: time and keys go in, the new state and what happened (a bounce, a line) come out, and a seed decides the dice, so a rule can be tested without playing.
+
+Apps used to hear only key presses. `KeyMapper::held()` says which keys are down, for a paddle that moves while a key is held and for Tetris's repeat. An App that is in use with no key pressed says so (`App::keepsScreenOn`): the screen stays lit, and an update waiting for a quiet moment keeps waiting. A Game left in the middle is found again paused. The best of each Game (for Pong, the longest rally) is kept in internal flash. Tetris plays Korobeiniki, the folk tune it has always had, a note at a time on a speaker channel of its own (`lib/games/src/tune.h`, host-tested timing); `0` switches it, `8` and `9` set its loudness, both kept; it hurries with each level. The beeps and the tune obey Settings > This device > Sound & LED.
+
 ## VPN
 
 A WireGuard tunnel (docs/milestones/N1.md), over whatever Wi-Fi the device is on: one peer, IPv4. Copy a client's `.conf` to the card as `/vpn/wg0.conf` and import it in Settings > Network > VPN (or `vpn import`); the configuration, private key included, is then kept in the device and never shown, and Settings offers to delete the file. A switch brings the tunnel up until the next restart; "Start with Wi-Fi" does it every time. It waits for the clock, which WireGuard needs. `VPN` shows in the Status Bar, bright once the server has answered.