feat: add root command and fix calc-02 exponent shortcuts

.memory/project.md

@@ -4,3 +4,5 @@
 - Read `.memory/state.md` for current state.
 - Keep names and commands in English.
 - Update memory files based on events: engine, demo, API, commands, exports, docs, or tasks.
+- Core arithmetic now includes `root` for y-th roots, and `samples/calc-02/` uses it for `y√x`.
+- `samples/calc-02/` in portrait mode remains the active responsive demo.

.memory/state.md

@@ -1,9 +1,9 @@
 # State
 - Core engine: `src/rpn-calculator.js`
-- Active demo: `samples/calc-02/` responsive HP48GX layout with HP48-like X-line editing; display-adjacent button row stays in 4 columns
+- Active demo: `samples/calc-02/` responsive HP48GX layout with portrait/landscape support; display-adjacent button row stays in 4 columns
 - Mode button shows the current angle mode only; selecting a mode uses a popup menu
 - Public API: `push`, `pop`, `clear`, `swap`, `remove`, `edit`, `isValidIndex`, `input`, `command`, `getOperationsByCategory`, `getConstants`
 - Config: `maxSize`, `base`, `angleMode`, `enabledCommands`
-- Commands: arithmetic, stack, trigonometry, constants `pi` and `e`
+- Commands: arithmetic, stack, trigonometry, constants `pi` and `e`; arithmetic now includes `root` for y-th roots
 - Demo actions: keyboard focus is kept on the hidden input on desktop so typing keeps working; the keypad layout places Enter in the bottom-left, ± in the former Enter position, and Esc before Clear for safety; paste parses clipboard text as a number before pushing it to the stack; Ctrl+V is supported via the hidden input paste event; backspace is ignored when the stack is empty; operation errors are shown as an overlay bar on top of the calculator with a shorter timeout and darker red
 - Exports: browser `window.RpnCalculator`, CommonJS `module.exports`

README.md

@@ -7,7 +7,7 @@ A browser-friendly RPN calculator built around a small, generic JavaScript API.
 This project provides:
 
 - a reusable JavaScript RPN engine in `src/rpn-calculator.js`
-- a browser demo in `samples/dev/`
+- browser demos in `samples/dev/` and `samples/calc-02/`
 - a command system centralized in a single operation dictionary
 - a small public API focused on stack operations and generic command dispatch
 
@@ -24,7 +24,7 @@ The main class is `RpnCalculator`.
 - `samples/calc-01/index.js`: demo UI and keyboard logic
 - `samples/calc-02/index.html`: new responsive HP48GX-style demo entry point
 - `samples/calc-02/index.css`: new responsive demo styles
-- `samples/calc-02/index.js`: new demo UI and keyboard logic
+- `samples/calc-02/index.js`: responsive HP48GX-style demo UI and keyboard logic
 - `samples/calc-XX/`: placeholder name for future demo variants
 
 ## Public API
@@ -110,6 +110,7 @@ calc.command('e');
 - `div` alias: `/`
 - `mod` alias: `%`
 - `pow` aliases: `^`, `y^x`
+- `root` aliases: `y√x`, `yroot`, `nroot`
 - `sqr`
 - `neg`
 - `sqrt` alias: `sqrt(x)`
@@ -134,6 +135,7 @@ calc.command('e');
 - `sqrt` accepts alias `sqrt(x)`
 - `recip` accepts alias `1/x`
 - `div` and `recip` throw `Division by zero` when needed
+- `root` computes the y-th root as `x^(1/y)` and throws `Invalid input for root` for invalid inputs
 - `sqrt` throws `Invalid input for sqrt` for negative values
 - `asin` and `acos` throw explicit domain errors outside `[-1, 1]`
 - `log` throws `Invalid input for log` for values `<= 0`
@@ -270,8 +272,8 @@ It keeps the calculator screen focused and updates the visible stack window as t
 
 ## Calc 02 demo
 
-`samples/calc-02/` is a new responsive HP48GX-inspired demo.
+`samples/calc-02/` is a responsive HP48GX-inspired demo.
-It adapts its layout to the browser window and switches between the supplied portrait and landscape arrangements.
+It adapts its layout to the browser window, supports portrait and landscape arrangements, and includes the `y√x` root operation.
 
 ## Exports
 

samples/calc-02/index.js

@@ -243,11 +243,17 @@ function execute(name) {
 			}
 		} else if (name === 'pow10') {
 			pushEditingValueIfNeeded();
+			const exponent = calc.stack[0];
+			calc.remove(0);
 			calc.push(10);
+			calc.push(exponent);
 			calc.command('pow');
 		} else if (name === 'exp') {
 			pushEditingValueIfNeeded();
+			const exponent = calc.stack[0];
+			calc.remove(0);
 			calc.push(Math.E);
+			calc.push(exponent);
 			calc.command('pow');
 		} else {
 			pushEditingValueIfNeeded();