feat(lessons): add lessons from client db

src/pages/student/lessons/LinearEquationsLesson.tsx

@@ -0,0 +1,504 @@
+import React, { useRef, useState, useEffect } from "react";
+import {
+  ArrowDown,
+  Check,
+  BookOpen,
+  Scale,
+  ArrowRight,
+  RotateCcw,
+} from "lucide-react";
+import LinearSolutionsWidget from "../../../components/lessons/LinearSolutionsWidget";
+import Quiz from "../../../components/lessons/Quiz";
+import { LINEAR_EQ_QUIZ_DATA } from "../../../utils/constants";
+import { Frac } from "../../../components/Math";
+
+interface LessonProps {
+  onFinish?: () => void;
+}
+
+const BalanceScaleWidget = () => {
+  const [left, setLeft] = useState(15);
+  const [right, setRight] = useState(15);
+  const [tilt, setTilt] = useState(0);
+  const [message, setMessage] = useState("Balanced");
+
+  const apply = (val: number, side: "both" | "left" | "right") => {
+    let newLeft = left;
+    let newRight = right;
+    if (side === "left" || side === "both") newLeft += val;
+    if (side === "right" || side === "both") newRight += val;
+    setLeft(newLeft);
+    setRight(newRight);
+    if (newLeft === newRight) {
+      setTilt(0);
+      setMessage("Perfectly Balanced! ✅");
+    } else if (newLeft > newRight) {
+      setTilt(-15);
+      setMessage("Unbalanced! Left side is heavier. ❌");
+    } else {
+      setTilt(15);
+      setMessage("Unbalanced! Right side is heavier. ❌");
+    }
+  };
+
+  const reset = () => {
+    setLeft(15);
+    setRight(15);
+    setTilt(0);
+    setMessage("Balanced");
+  };
+
+  return (
+    <div className="bg-white p-6 rounded-xl shadow-lg border border-slate-200">
+      <div className="flex justify-between items-center mb-8">
+        <h3 className="font-bold text-slate-700">Algebra Balance Scale</h3>
+        <button onClick={reset} className="text-slate-400 hover:text-slate-600">
+          <RotateCcw className="w-4 h-4" />
+        </button>
+      </div>
+      <div className="relative h-40 w-full mb-8 flex justify-center items-end">
+        <div className="absolute bottom-0 w-0 h-0 border-l-[20px] border-l-transparent border-r-[20px] border-r-transparent border-b-[40px] border-b-slate-800"></div>
+        <div
+          className="w-64 h-2 bg-slate-600 absolute bottom-[40px] transition-transform duration-700"
+          style={{ transform: `rotate(${tilt}deg)` }}
+        >
+          <div
+            className="absolute left-0 top-0 flex flex-col items-center"
+            style={{ transform: `translateY(0px) rotate(${-tilt}deg)` }}
+          >
+            <div className="w-20 h-20 border-b-4 border-l-2 border-r-2 border-slate-400 rounded-b-xl bg-slate-50 flex items-center justify-center shadow-inner relative top-2">
+              <span className="font-bold text-blue-600 text-lg">{left} kg</span>
+            </div>
+            <div className="w-0.5 h-16 bg-slate-400 absolute -top-16"></div>
+          </div>
+          <div
+            className="absolute right-0 top-0 flex flex-col items-center"
+            style={{ transform: `translateY(0px) rotate(${-tilt}deg)` }}
+          >
+            <div className="w-20 h-20 border-b-4 border-l-2 border-r-2 border-slate-400 rounded-b-xl bg-slate-50 flex items-center justify-center shadow-inner relative top-2">
+              <span className="font-bold text-emerald-600 text-lg">
+                {right} kg
+              </span>
+            </div>
+            <div className="w-0.5 h-16 bg-slate-400 absolute -top-16"></div>
+          </div>
+        </div>
+      </div>
+      <div
+        className={`text-center font-bold mb-6 ${tilt === 0 ? "text-green-600" : "text-rose-600"}`}
+      >
+        {message}
+      </div>
+      <div className="grid grid-cols-2 gap-4">
+        <button
+          onClick={() => apply(-5, "left")}
+          className="p-3 rounded-lg border-2 border-slate-200 hover:border-rose-300 hover:bg-rose-50 text-slate-600 text-sm font-bold transition-all"
+        >
+          Subtract 5 from Left ONLY
+        </button>
+        <button
+          onClick={() => apply(-5, "both")}
+          className="p-3 rounded-lg border-2 border-blue-500 bg-blue-50 hover:bg-blue-100 text-blue-700 text-sm font-bold transition-all shadow-sm"
+        >
+          Subtract 5 from BOTH sides
+        </button>
+      </div>
+      <p className="text-xs text-center text-slate-400 mt-4">
+        Goal: Keep the scale balanced while isolating the variable.
+      </p>
+    </div>
+  );
+};
+
+const LinearEquationsLesson: React.FC<LessonProps> = ({ onFinish }) => {
+  const [activeSection, setActiveSection] = useState(0);
+  const sectionsRef = useRef<(HTMLElement | null)[]>([]);
+
+  const scrollToSection = (index: number) => {
+    setActiveSection(index);
+    sectionsRef.current[index]?.scrollIntoView({
+      behavior: "smooth",
+      block: "start",
+    });
+  };
+
+  useEffect(() => {
+    const observer = new IntersectionObserver(
+      (entries) => {
+        entries.forEach((entry) => {
+          if (entry.isIntersecting) {
+            const index = sectionsRef.current.indexOf(
+              entry.target as HTMLElement,
+            );
+            if (index !== -1) setActiveSection(index);
+          }
+        });
+      },
+      { rootMargin: "-20% 0px -60% 0px" },
+    );
+    sectionsRef.current.forEach((section) => {
+      if (section) observer.observe(section);
+    });
+    return () => observer.disconnect();
+  }, []);
+
+  const SectionMarker = ({
+    index,
+    title,
+    icon: Icon,
+  }: {
+    index: number;
+    title: string;
+    icon: any;
+  }) => {
+    const isActive = activeSection === index;
+    const isPast = activeSection > index;
+    return (
+      <button
+        onClick={() => scrollToSection(index)}
+        className={`flex items-center gap-3 p-3 w-full rounded-lg transition-all ${isActive ? "bg-white shadow-md border border-blue-100" : "hover:bg-slate-100"}`}
+      >
+        <div
+          className={`w-8 h-8 rounded-full flex items-center justify-center shrink-0 ${isActive ? "bg-blue-600 text-white" : isPast ? "bg-blue-400 text-white" : "bg-slate-200 text-slate-500"}`}
+        >
+          {isPast ? (
+            <Check className="w-4 h-4" />
+          ) : (
+            <Icon className="w-4 h-4" />
+          )}
+        </div>
+        <div className="text-left">
+          <p
+            className={`text-sm font-bold ${isActive ? "text-blue-900" : "text-slate-600"}`}
+          >
+            {title}
+          </p>
+        </div>
+      </button>
+    );
+  };
+
+  return (
+    <div className="flex flex-col lg:flex-row min-h-screen">
+      <aside className="w-full lg:w-64 lg:fixed lg:top-20 lg:bottom-0 lg:overflow-y-auto p-4 border-r border-slate-200 bg-slate-50 z-0 hidden lg:block">
+        <nav className="space-y-2">
+          <SectionMarker index={0} title="The Balance Principle" icon={Scale} />
+          <SectionMarker
+            index={1}
+            title="Number of Solutions"
+            icon={ArrowRight}
+          />
+          <SectionMarker index={2} title="Practice" icon={BookOpen} />
+        </nav>
+      </aside>
+
+      <div className="flex-1 lg:ml-64 p-6 md:p-12 max-w-4xl mx-auto">
+        {/* Section 1: Balance Principle */}
+        <section
+          ref={(el) => {
+            sectionsRef.current[0] = el;
+          }}
+          className="min-h-screen flex flex-col justify-center mb-24 pt-20 lg:pt-0"
+        >
+          <h2 className="text-4xl font-extrabold text-slate-900 mb-6">
+            The Balance Principle
+          </h2>
+          <div className="prose prose-slate text-lg text-slate-600 mb-6">
+            <p>
+              Linear equations are like a balance scale. Whatever you do to one
+              side, you <strong>must</strong> do to the other. The goal is
+              always to <strong>isolate the variable</strong> — get x by itself
+              on one side with a number on the other.
+            </p>
+          </div>
+
+          <BalanceScaleWidget />
+
+          {/* 4-Step Process */}
+          <div className="mt-8 bg-blue-50 border border-blue-200 rounded-2xl p-6 space-y-4">
+            <h3 className="font-bold text-blue-900 text-lg">
+              The 4-Step Solve Process
+            </h3>
+            <div className="space-y-3">
+              {[
+                {
+                  step: "1",
+                  title: "Distribute",
+                  desc: "Expand parentheses and clear fractions by multiplying through by the LCD (lowest common denominator).",
+                },
+                {
+                  step: "2",
+                  title: "Combine Like Terms",
+                  desc: "Simplify each side of the equation separately — add/subtract terms with the same variable.",
+                },
+                {
+                  step: "3",
+                  title: "Move",
+                  desc: "Get all variable terms on one side, all constant terms on the other, using addition or subtraction.",
+                },
+                {
+                  step: "4",
+                  title: "Divide",
+                  desc: "Divide both sides by the coefficient of the variable to solve.",
+                },
+              ].map((item) => (
+                <div
+                  key={item.step}
+                  className="flex gap-4 bg-white rounded-xl p-4 border border-blue-100"
+                >
+                  <div className="w-8 h-8 bg-blue-600 text-white rounded-full flex items-center justify-center font-bold shrink-0">
+                    {item.step}
+                  </div>
+                  <div>
+                    <p className="font-bold text-slate-800">{item.title}</p>
+                    <p className="text-slate-600 text-sm">{item.desc}</p>
+                  </div>
+                </div>
+              ))}
+            </div>
+          </div>
+
+          {/* Three Worked Examples */}
+          <div className="mt-8 space-y-4">
+            <div className="bg-emerald-50 border border-emerald-200 rounded-xl p-6">
+              <p className="font-bold text-emerald-800 mb-3">
+                Example 1: Basic (no fractions)
+              </p>
+              <div className="font-mono text-sm space-y-1 text-slate-700">
+                <p>Solve: 3(2x − 4) = 2x + 8</p>
+                <p className="text-slate-500">
+                  Step 1 (Distribute): 6x − 12 = 2x + 8
+                </p>
+                <p className="text-slate-500">Step 3 (Move): 4x = 20</p>
+                <p className="text-slate-500">
+                  Step 4 (Divide by 4):{" "}
+                  <strong className="text-emerald-700">x = 5</strong>
+                </p>
+              </div>
+            </div>
+            <div className="bg-emerald-50 border border-emerald-200 rounded-xl p-6">
+              <p className="font-bold text-emerald-800 mb-3">
+                Example 2: With fractions — clear them first!
+              </p>
+              <div className="font-mono text-sm space-y-1 text-slate-700">
+                <p>
+                  Solve: <Frac n="x" d="3" /> + 2 = <Frac n="x" d="2" /> − 1
+                </p>
+                <p className="text-slate-500">
+                  Multiply every term by 6 (LCD of 3 and 2):
+                </p>
+                <p className="text-slate-500">2x + 12 = 3x − 6</p>
+                <p className="text-slate-500">12 + 6 = 3x − 2x</p>
+                <p className="text-slate-500">
+                  <strong className="text-emerald-700">x = 18</strong>
+                </p>
+              </div>
+            </div>
+            <div className="bg-emerald-50 border border-emerald-200 rounded-xl p-6">
+              <p className="font-bold text-emerald-800 mb-3">
+                Example 3: Literal equations (isolating a variable)
+              </p>
+              <div className="font-mono text-sm space-y-1 text-slate-700">
+                <p>Solve for r: A = P(1 + rt)</p>
+                <p className="text-slate-500">
+                  Divide both sides by P: <Frac n="A" d="P" /> = 1 + rt
+                </p>
+                <p className="text-slate-500">
+                  Subtract 1: <Frac n="A" d="P" /> − 1 = rt
+                </p>
+                <p className="text-slate-500">
+                  Divide by t:{" "}
+                  <strong className="text-emerald-700">
+                    r ={" "}
+                    <Frac
+                      n={
+                        <>
+                          <Frac n="A" d="P" /> − 1
+                        </>
+                      }
+                      d="t"
+                    />
+                  </strong>
+                </p>
+              </div>
+            </div>
+          </div>
+
+          <div className="mt-6 bg-red-50 border border-red-200 rounded-xl p-4 text-sm">
+            <p className="font-bold text-red-800 mb-1">
+              Common SAT Mistake: Distributing a Negative
+            </p>
+            <p className="text-slate-700">
+              When distributing a negative sign: −3(x − 4) = −3x + 12, NOT −3x −
+              12. The negative multiplies EVERY term inside the parentheses.
+            </p>
+          </div>
+
+          <button
+            onClick={() => scrollToSection(1)}
+            className="mt-8 group flex items-center text-blue-600 font-bold hover:text-blue-800 transition-colors"
+          >
+            Next: Number of Solutions{" "}
+            <ArrowDown className="ml-2 w-5 h-5 group-hover:translate-y-1 transition-transform" />
+          </button>
+        </section>
+
+        {/* Section 2: Number of Solutions */}
+        <section
+          ref={(el) => {
+            sectionsRef.current[1] = el;
+          }}
+          className="min-h-screen flex flex-col justify-center mb-24"
+        >
+          <h2 className="text-4xl font-extrabold text-slate-900 mb-6">
+            One, None, or Infinite Solutions?
+          </h2>
+          <div className="prose prose-slate text-lg text-slate-600 mb-8">
+            <p>
+              Not all equations have exactly one answer. After simplifying, look
+              at what's left. The SAT frequently asks for a value of <em>k</em>{" "}
+              that makes an equation have no solution or infinitely many
+              solutions — this is a critical concept to master.
+            </p>
+          </div>
+
+          <div className="bg-blue-50 border border-blue-200 rounded-2xl p-6 mb-8 space-y-4">
+            <h3 className="text-lg font-bold text-blue-900">
+              The Three Outcomes
+            </h3>
+            <div className="grid grid-cols-1 md:grid-cols-3 gap-4">
+              <div className="bg-blue-100 rounded-xl p-4 text-center">
+                <div className="font-bold text-blue-900 text-base mb-2">
+                  One Solution
+                </div>
+                <div className="font-mono text-sm text-blue-700 bg-white rounded p-2 mb-2">
+                  2x + 1 = x + 5
+                </div>
+                <div className="text-xs text-blue-700">
+                  Variable survives after simplification → unique answer:{" "}
+                  <strong>x = 4</strong>
+                </div>
+              </div>
+              <div className="bg-red-50 border border-red-200 rounded-xl p-4 text-center">
+                <div className="font-bold text-red-900 text-base mb-2">
+                  No Solution
+                </div>
+                <div className="font-mono text-sm text-red-700 bg-white rounded p-2 mb-2">
+                  2x + 3 = 2x + 5
+                </div>
+                <div className="text-xs text-red-700">
+                  Variables cancel → <strong>3 = 5</strong> (false statement —
+                  impossible)
+                </div>
+              </div>
+              <div className="bg-emerald-50 border border-emerald-200 rounded-xl p-4 text-center">
+                <div className="font-bold text-emerald-900 text-base mb-2">
+                  Infinite Solutions
+                </div>
+                <div className="font-mono text-sm text-emerald-700 bg-white rounded p-2 mb-2">
+                  2x + 3 = 2x + 3
+                </div>
+                <div className="text-xs text-emerald-700">
+                  Variables cancel → <strong>3 = 3</strong> (always true — every
+                  x works)
+                </div>
+              </div>
+            </div>
+          </div>
+
+          {/* Finding k */}
+          <div className="bg-blue-50 border border-blue-200 rounded-2xl p-6 mb-8 space-y-4">
+            <h3 className="text-lg font-bold text-blue-900">
+              SAT Focus: Finding the Value of k
+            </h3>
+
+            <div className="bg-white rounded-xl p-5 border border-blue-100">
+              <p className="font-bold text-blue-800 mb-3">
+                Example: For what value of k does 4x + k = 4x − 2 have no
+                solution?
+              </p>
+              <div className="font-mono text-sm text-slate-700 space-y-1">
+                <p>After subtracting 4x from both sides: k = −2</p>
+                <p>
+                  If k = −2: −2 = −2 (always true) → infinite solutions, not no
+                  solution!
+                </p>
+                <p className="text-blue-700 font-bold">
+                  For no solution: k ≠ −2 (any other value gives a false
+                  statement like k = −2 being false)
+                </p>
+              </div>
+              <p className="text-slate-500 text-xs mt-2">
+                The equation has no solution for any value of k EXCEPT −2. For
+                infinite solutions, set k = −2.
+              </p>
+            </div>
+
+            <div className="bg-white rounded-xl p-5 border border-blue-100">
+              <p className="font-bold text-blue-800 mb-3">
+                Example: For what value of k does 3(x + k) = 3x + 12 have
+                infinite solutions?
+              </p>
+              <div className="font-mono text-sm text-slate-700 space-y-1">
+                <p>Distribute: 3x + 3k = 3x + 12</p>
+                <p>Subtract 3x: 3k = 12</p>
+                <p className="text-blue-700 font-bold">k = 4</p>
+              </div>
+              <p className="text-slate-500 text-xs mt-2">
+                For k = 4: 12 = 12 (always true) → infinite solutions. ✓
+              </p>
+            </div>
+
+            <div className="bg-red-50 border border-red-200 rounded-xl p-4 text-sm">
+              <p className="font-bold text-red-800 mb-1">The Key Rule</p>
+              <p className="text-slate-700">
+                <strong>No solution</strong>: same variable coefficients,
+                different constants (parallel lines).
+                <br />
+                <strong>Infinite solutions</strong>: same variable coefficients
+                AND same constants (identical lines).
+              </p>
+            </div>
+          </div>
+
+          <LinearSolutionsWidget />
+          <button
+            onClick={() => scrollToSection(2)}
+            className="mt-12 group flex items-center text-blue-600 font-bold hover:text-blue-800 transition-colors"
+          >
+            Next: Practice Quiz{" "}
+            <ArrowDown className="ml-2 w-5 h-5 group-hover:translate-y-1 transition-transform" />
+          </button>
+        </section>
+
+        {/* Section 3: Quiz */}
+        <section
+          ref={(el) => {
+            sectionsRef.current[2] = el;
+          }}
+          className="min-h-screen flex flex-col justify-center"
+        >
+          <h2 className="text-4xl font-extrabold text-slate-900 mb-8">
+            Practice Time
+          </h2>
+          {LINEAR_EQ_QUIZ_DATA.map((quiz, idx) => (
+            <div key={quiz.id} className="mb-12">
+              <Quiz data={quiz} />
+            </div>
+          ))}
+          <div className="p-8 bg-blue-900 rounded-2xl text-white text-center mt-12">
+            <h3 className="text-2xl font-bold mb-4">Topic Mastered!</h3>
+            <button
+              onClick={onFinish}
+              className="px-6 py-3 bg-white text-blue-900 font-bold rounded-full hover:bg-blue-50 transition-colors"
+            >
+              Finish Lesson ✓
+            </button>
+          </div>
+        </section>
+      </div>
+    </div>
+  );
+};
+
+export default LinearEquationsLesson;