functle

@@ -4,7 +4,7 @@

         <style>

             body { font-family: sans-serif; }

             #plot { border: 1px solid #000; }

-            #grid { border-collapse: collapse; margin-top: 10px; }

+            #grid { border-collapse: separate; border-spacing: 5px 10px; margin-top: 10px; }

             #grid td { width: 40px; height: 40px; border: 1px solid #ccc; text-align: center; vertical-align: middle; font-weight: bold; }

             .grey { background: #787c7e; color: #fff; }

             .yellow { background: #c9b458; color: #fff; }

@@ -32,8 +32,51 @@

                 unary: ["^2", "^3", "sin", "exp", "ln"],

                 binary: ["+", "-", "*", "/"]

             };

-            const target = ["x", "sin", "1", "1", "+", "*"]; // 2*sin(x)

-            const tl = target.length;

+            const allTokens = [...allowed.terminals, ...allowed.unary, ...allowed.binary];

+            const tl = 6;

+            

+            function evalPostfix(tokens, x) {

+                const s = [];

+                for (const t of tokens) {

+                    if (t === "x") s.push(x);

+                    else if (t === "1") s.push(1);

+                    else if (t === "2") s.push(2);

+                    else if (allowed.unary.includes(t)) {

+                        if (s.length < 1) throw 0;

+                        const v = s.pop();

+                        if (t === "^2") s.push(v ** 2);

+                        if (t === "^3") s.push(v ** 3);

+                        if (t === "sin") s.push(Math.sin(v));

+                        if (t === "exp") s.push(Math.exp(v));

+                        if (t === "ln") s.push(Math.log(v));

+                    } else if (allowed.binary.includes(t)) {

+                        if (s.length < 2) throw 0;

+                        const b = s.pop(), a = s.pop();

+                        if (t === "+") s.push(a + b);

+                        if (t === "-") s.push(a - b);

+                        if (t === "*") s.push(a * b);

+                        if (t === "/") s.push(a / b);

+                    } else throw 0;

+                }

+                if (s.length !== 1) throw 0;

+                return s[0];

+            }

+            

+            function generateTarget() {

+                while (true) {

+                    const cand = [];

+                    for (let i = 0; i < tl; i++) {

+                        cand.push(allTokens[Math.floor(Math.random() * allTokens.length)]);

+                    }

+                    try {

+                        // test on a sample of x values to ensure valid

+                        for (let xTest of [0, 1, -1]) evalPostfix(cand, xTest);

+                        return cand;

+                    } catch (e) { continue; }

+                }

+            }

+            

+            const target = generateTarget();

             const maxGuesses = 6;

             let currentRow = 0;

             const width = 400, height = 400;

@@ -57,13 +101,11 @@

                 const x0 = mapX(0);

                 ctx.moveTo(x0, 0);

                 ctx.lineTo(x0, height);

-                // ticks at (1,0) and (-1,0)

                 [1, -1].forEach(val => {

                     const px = mapX(val);

                     ctx.moveTo(px, y0 - 5);

                     ctx.lineTo(px, y0 + 5);

                 });

-                // ticks at (0,1) and (0,-1)

                 [1, -1].forEach(val => {

                     const py = mapY(val);

                     ctx.moveTo(x0 - 5, py);

@@ -90,9 +134,10 @@

                     drawCurve(ys, color);

                 });

             }

-            // initial draw

+            

             drawAxes();

             drawCurve(targetYs, "green");

+            

             const grid = document.getElementById("grid");

             for (let i = 0; i < maxGuesses; i++) {

                 const tr = document.createElement("tr");

@@ -110,7 +156,7 @@

                     return;

                 }

                 for (const t of inp) {

-                    if (![...allowed.terminals, ...allowed.unary, ...allowed.binary].includes(t)) {

+                    if (!allTokens.includes(t)) {

                         document.getElementById("message").textContent = "Invalid token: " + t;

                         return;

                     }

@@ -137,31 +183,7 @@

                     document.getElementById("submitBtn").disabled = true;

                 }

             };

-            function evalPostfix(tokens, x) {

-                const s = [];

-                for (const t of tokens) {

-                    if (t === "x") s.push(x);

-                    else if (t === "1") s.push(1);

-                    else if (t === "2") s.push(2);

-                    else if (allowed.unary.includes(t)) {

-                        const v = s.pop();

-                        if (t === "^2") s.push(v ** 2);

-                        if (t === "^3") s.push(v ** 3);

-                        if (t === "sin") s.push(Math.sin(v));

-                        if (t === "exp") s.push(Math.exp(v));

-                        if (t === "ln") s.push(Math.log(v));

-                    } else {

-                        const b = s.pop(), a = s.pop();

-                        if (t === "+") s.push(a + b);

-                        if (t === "-") s.push(a - b);

-                        if (t === "*") s.push(a * b);

-                        if (t === "/") s.push(a / b);

-                    }

-                    if (s.length < 0) throw 0;

-                }

-                if (s.length !== 1) throw 0;

-                return s[0];

-            }

+            

             function closeEnough(a, b) {

                 for (let i = 0; i < a.length; i++) {

                     if (isNaN(a[i]) || Math.abs(a[i] - b[i]) > 0.1 * (Math.abs(b[i]) + 1)) return false;