docs: update calc-02 shortcut reference and key mappings

Keep the calculator stack unlimited in the demo and only constrain the rendered stack view. Also restore the edit cursor position when pulling a value into the input from the stack.

.memory/project.md

@@ -1,7 +1,8 @@
 # State
 - Core engine: `src/rpn-calculator.js`
-- Reference demo: `samples/calc-02/` (portrait-first HP48GX layout, compact mode/constants popups; Const button comes before Mode in the display row)
+- Reference demo: `samples/calc-02/` (portrait-first HP48GX layout; calc-02 keyboard shortcuts are the reference; compact mode/constants popups; Const button comes before Mode in the display row)
 - Important UI behavior: mode button shows the current angle mode; keyboard focus stays on the hidden input on desktop; clipboard paste is supported
+- Note: keep scrolling behavior in mind for the calc-02 demo when changing the stack/UI layout
 - Public API: `push`, `pop`, `clear`, `swap`, `remove`, `edit`, `isValidIndex`, `input`, `command`, `getOperationsByCategory`, `getConstants`, `listConstants`, `setConstant`, `removeConstant`, `hasConstant`
 - Config: `maxSize`, `base`, `angleMode`, `enabledCommands`
 - Commands: arithmetic, stack, trigonometry, constants `pi` and `e`; arithmetic includes `root`; constants can be added or removed dynamically through the core API

README.md

@@ -275,12 +275,15 @@ The current demo supports:
 - `Escape`
 - `ArrowUp`, `ArrowDown`, `ArrowRight`
 - `+`, `-`, `*`, `/`, `%`, `^`
-- `q`, `n`, `r`, `i`, `g`, `l`, `s`, `c`, `S`, `C`
-- `x`, `y`, `z`, `t`
+- `s`, `S`, `r`, `R`, `v`, `u`
+- `l`, `L`, `n`, `N`, `e`, `E`
+- `i`, `o`, `a`, `I`, `O`, `A`
 
 The demo also implements stack selection and stack-item move mode in its UI layer using the public calculator methods.
 It keeps the calculator screen focused and updates the visible stack window as the selection moves.
 
+Note: `calc-02` keyboard shortcuts are the reference for this project.
+
 ## Exports
 
 `RpnCalculator` is exposed in both environments:

samples/calc-02/index.css

@@ -137,6 +137,10 @@ body {
 	justify-self: end;
 	font-size: 20px;
 }
+
+.stack-value.is-editing {
+	letter-spacing: 0.02em;
+}
 .display-buttons-panel {
 	padding: 8px;
 	min-height: 0;
@@ -379,6 +383,37 @@ button:active {
 	outline-offset: 2px;
 }
 
+.stack-value.is-editing {
+	display: inline-flex;
+	align-items: center;
+	justify-content: flex-end;
+	gap: 0;
+}
+
+.edit-text {
+	display: inline-block;
+	white-space: pre;
+}
+
+.edit-caret {
+	display: inline-block;
+	width: 1px;
+	height: 1em;
+	margin: 0 0.12ch;
+	background: currentColor;
+	animation: caret-blink 1s steps(1, end) infinite;
+	transform: translateY(0.02em);
+}
+
+@keyframes caret-blink {
+	0%, 49% {
+		opacity: 1;
+	}
+	50%, 100% {
+		opacity: 0.15;
+	}
+}
+
 .key-default {
 	background: linear-gradient(180deg, var(--btnTop), var(--btnBottom));
 	color: #eef2f7;

samples/calc-02/index.js

@@ -94,6 +94,7 @@ function focusInput() {
 }
 
 let statusTimer = null;
+let editCursor = 0;
 
 function setStatus(message, isError = false, timeoutMs = 1400) {
 	if (!statusLine) return;
@@ -118,27 +119,17 @@ function clearStatus() {
 	statusLine.classList.remove('is-error');
 }
 
-function normalizeStack() {
-	while (calc.stack.length > 4) {
-		calc.stack.shift();
-	}
-}
-
 function getStackLine(indexFromTop) {
 	return indexFromTop >= 0 && indexFromTop < calc.stack.length ? calc.stack[indexFromTop] : '';
 }
 
 function getStackDisplayValue(label) {
-	if (label === 'X') {
-		return calc.isEditing ? calc.inputValue : (calc.formatNumber(getStackLine(0)) || '');
+	if (label === 'X' && calc.isEditing) {
+		return calc.inputValue;
 	}
-	if (label === 'Y') {
-		return calc.isEditing ? (calc.formatNumber(getStackLine(0)) || '') : (calc.formatNumber(getStackLine(1)) || '');
-	}
-	if (label === 'Z') {
-		return calc.isEditing ? (calc.formatNumber(getStackLine(1)) || '') : (calc.formatNumber(getStackLine(2)) || '');
-	}
-	return calc.isEditing ? (calc.formatNumber(getStackLine(2)) || '') : (calc.formatNumber(getStackLine(3)) || '');
+	const indexMap = { X: 0, Y: 1, Z: 2, T: 3 };
+	const indexFromTop = calc.isEditing ? Math.max(0, indexMap[label] - 1) : indexMap[label];
+	return calc.formatNumber(getStackLine(indexFromTop)) || '';
 }
 
 function updateCopyButtons() {
@@ -152,19 +143,40 @@ function updateCopyButtons() {
 	}
 }
 
+function renderEditValue() {
+	const cursor = Math.max(0, Math.min(editCursor, calc.inputValue.length));
+	stackEls.X.innerHTML = `<span class="edit-text">${calc.inputValue.slice(0, cursor)}</span><span class="edit-caret" aria-hidden="true"></span><span class="edit-text">${calc.inputValue.slice(cursor)}</span>`;
+}
+
 function render() {
-	normalizeStack();
 	const isPortrait = window.matchMedia('(orientation: portrait)').matches || window.innerWidth <= 860;
 	calculatorEl?.classList.toggle('portrait', isPortrait);
 	calculatorEl?.classList.toggle('landscape', !isPortrait);
-	stackEls.X.textContent = getStackDisplayValue('X');
+	stackEls.X.textContent = calc.isEditing ? '' : getStackDisplayValue('X');
+	if (calc.isEditing) {
+		renderEditValue();
+	}
 	stackEls.Y.textContent = getStackDisplayValue('Y');
 	stackEls.Z.textContent = getStackDisplayValue('Z');
 	stackEls.T.textContent = getStackDisplayValue('T');
+	stackEls.X.classList.toggle('is-editing', calc.isEditing);
+	stackEls.X.classList.toggle('is-caret-visible', calc.isEditing);
 	updateCopyButtons();
 	modeButton.textContent = calc.angleMode;
 }
 
+function stopEditing(clearValue = false) {
+	if (clearValue) {
+		calc.inputValue = '';
+	}
+	calc.isEditing = false;
+	editCursor = 0;
+}
+
+function moveEditCursor(delta) {
+	editCursor = Math.max(0, Math.min(calc.inputValue.length, editCursor + delta));
+}
+
 function pushEditingValueIfNeeded() {
 	if (!calc.isEditing) return;
 	if (calc.inputValue !== '') {
@@ -172,20 +184,36 @@ function pushEditingValueIfNeeded() {
 	}
 	calc.inputValue = '';
 	calc.isEditing = false;
+	editCursor = 0;
+}
+
+function startEditingFromStackTop() {
+	if (!calc.isValidIndex(0)) return false;
+	const value = calc.stack[0];
+	calc.remove(0);
+	calc.isEditing = true;
+	calc.inputValue = calc.formatNumber(value);
+	editCursor = calc.inputValue.length;
+	return true;
 }
 
 function inputToX(value) {
 	if (!calc.isEditing) {
 		calc.isEditing = true;
 		calc.inputValue = '';
+		editCursor = 0;
 	}
 	if (value === 'Backspace') {
-		calc.inputValue = calc.inputValue.slice(0, -1);
+		if (editCursor > 0) {
+			calc.inputValue = `${calc.inputValue.slice(0, editCursor - 1)}${calc.inputValue.slice(editCursor)}`;
+			editCursor -= 1;
+		}
 	} else {
-		calc.inputValue += value;
+		calc.inputValue = `${calc.inputValue.slice(0, editCursor)}${value}${calc.inputValue.slice(editCursor)}`;
+		editCursor += value.length;
 	}
 	if (calc.inputValue === '') {
-		calc.isEditing = false;
+		stopEditing();
 	}
 }
 
@@ -217,11 +245,9 @@ function execute(name) {
 			}
 		} else if (name === 'clear') {
 			calc.clear();
-			calc.inputValue = '';
-			calc.isEditing = false;
+			stopEditing(true);
 		} else if (name === 'escape') {
-			calc.inputValue = '';
-			calc.isEditing = false;
+			stopEditing(true);
 		} else if (name === 'backspace') {
 			if (calc.isEditing) {
 				inputToX('Backspace');
@@ -235,7 +261,9 @@ function execute(name) {
 			}
 		} else if (name === 'neg') {
 			if (calc.isEditing) {
-				calc.inputValue = calc.inputValue.startsWith('-') ? calc.inputValue.slice(1) : `-${calc.inputValue}`;
+				const hasSign = calc.inputValue.startsWith('-');
+				calc.inputValue = hasSign ? calc.inputValue.slice(1) : `-${calc.inputValue}`;
+				moveEditCursor(hasSign ? -1 : 1);
 			} else {
 				calc.command('neg');
 			}
@@ -243,6 +271,9 @@ function execute(name) {
 			pushEditingValueIfNeeded();
 			calc.command(name);
 		}
+		if (!calc.isEditing) {
+			editCursor = 0;
+		}
 		render();
 	} catch (error) {
 		setStatus(error?.message || 'Operation error', true);
@@ -305,16 +336,53 @@ function handleKeyboard(event) {
 		'/': 'div',
 		'%': 'mod',
 		'^': 'pow',
+		s: 'sqr',
+		S: 'pow',
+		r: 'sqrt',
+		R: 'root',
+		v: 'recip',
+		u: 'pow10',
+		l: 'log',
+		L: 'log',
+		n: 'ln',
+		N: 'ln',
+		e: 'exp',
+		E: 'exp',
+		i: 'sin',
+		o: 'cos',
+		a: 'tan',
+		I: 'asin',
+		O: 'acos',
+		A: 'atan',
 	};
-	const arrowMap = {
-		ArrowUp: upButton,
-		ArrowDown: downButton,
-		ArrowLeft: leftButton,
-		ArrowRight: rightButton,
-	};
-	if (arrowMap[key]) {
+	if (key === 'ArrowLeft') {
 		event.preventDefault();
-		arrowMap[key].click();
+		if (calc.isEditing) {
+			moveEditCursor(-1);
+			render();
+			return;
+		}
+		leftButton.click();
+		return;
+	}
+	if (key === 'ArrowRight') {
+		event.preventDefault();
+		if (calc.isEditing) {
+			moveEditCursor(1);
+			render();
+			return;
+		}
+		rightButton.click();
+		return;
+	}
+	if (key === 'ArrowUp') {
+		event.preventDefault();
+		upButton.click();
+		return;
+	}
+	if (key === 'ArrowDown') {
+		event.preventDefault();
+		downButton.click();
 		return;
 	}
 	if (map[key]) {
@@ -420,7 +488,7 @@ const constantLabels = {
 	e: 'e',
 	phi: 'φ',
 	g: 'g',
-	c: 'c',
+	c: 'C',
 };
 const constantOrder = ['pi', 'e', 'phi', 'g', 'c'];
 
@@ -459,19 +527,28 @@ constButton.addEventListener('click', (event) => {
 	toggleConstMenu();
 });
 
-leftButton.addEventListener('click', () => {});
+leftButton.addEventListener('click', () => {
+	if (calc.isEditing) {
+		moveEditCursor(-1);
+		render();
+		focusInput();
+	}
+});
 downButton.addEventListener('click', () => {
-	if (!calc.isEditing && calc.isValidIndex(0)) {
-		const value = calc.stack[0];
-		calc.remove(0);
-		calc.isEditing = true;
-		calc.inputValue = calc.formatNumber(value);
+	if (!calc.isEditing && startEditingFromStackTop()) {
 		render();
 		focusInput();
 	}
 });
 
+
 rightButton.addEventListener('click', () => {
+	if (calc.isEditing) {
+		moveEditCursor(1);
+		render();
+		focusInput();
+		return;
+	}
 	execute('swap');
 });