diff --git a/simulasi-mk.html b/simulasi-mk.html
index bdb29b1..e10770f 100644
--- a/simulasi-mk.html
+++ b/simulasi-mk.html
@@ -25,8 +25,13 @@
         .course-card.dragging { opacity: 0.5; border: 2px dashed #a8a29e; background-color: #f5f5f4; }
         
         /* Drop Zone Styles */
-        .semester-list { min-height: 120px; transition: background-color 0.2s; }
-        .semester-list.drag-over { background-color: #f0fdf4; border: 2px dashed #4ade80; }
+        .semester-list { min-height: 120px; transition: background-color 0.2s, opacity 0.2s; }
+        
+        /* Valid Drop Target */
+        .semester-list.valid-target { background-color: #f0fdf4; border: 2px dashed #4ade80; }
+        
+        /* Invalid Drop Target (Wrong Parity) */
+        .semester-list.invalid-target { opacity: 0.3; background-color: #e5e5e5; pointer-events: none; border: 2px solid #d4d4d4; }
         
         /* Warning States */
         .semester-container { transition: all 0.3s; }
@@ -54,11 +59,10 @@
 </head>
 <body class="bg-stone-50 text-stone-800">
 
-    <!-- Chosen Palette: Warm Neutrals (Stone) with Logic-based Alerts (Red/Green) -->
+    <!-- Chosen Palette: Warm Neutrals with Logic Alerts -->
     <!-- Application Structure Plan: 
-         - Added "GPA Simulation" controls to each semester header.
-         - Semester containers now react visually to SKS Overload based on previous semester's GPA.
-         - Drag & Drop enables users to "Fail/Postpone" courses to future semesters to fit the SKS limit.
+         - Updated Drag & Drop Logic: Enforce Odd/Even semester constraints.
+         - Visual Feedback: Grey out invalid semesters when dragging.
     -->
     <!-- CONFIRMATION: NO SVG graphics used. NO Mermaid JS used. -->
 
@@ -68,7 +72,9 @@
         <header class="mb-10 text-center">
             <h1 class="text-3xl md:text-4xl font-bold text-stone-900 mb-4">Simulasi Perjalanan Mahasiswa & KRS</h1>
             <p class="text-lg text-stone-600 max-w-3xl mx-auto">
-                Atur strategi studimu. <span class="font-bold text-orange-600">Simulasikan IP rendah</span>, lihat dampak batas SKS, dan geser mata kuliah untuk menyusun ulang rencana (mengulang/menunda).
+                Atur strategi studimu. <span class="font-bold text-orange-600">Simulasikan IP rendah</span>, lihat dampak batas SKS, dan geser mata kuliah untuk menyusun ulang rencana.
+                <br>
+                <span class="text-sm bg-red-100 text-red-800 px-2 py-1 rounded mt-2 inline-block font-bold">Aturan Baru: MK Ganjil hanya bisa ke Sem Ganjil, Genap ke Genap.</span>
             </p>
             
             <div class="mt-6 flex flex-wrap justify-center gap-4 text-sm">
@@ -169,7 +175,7 @@
                 </div>
             </div>
 
-            <div class="semester-list p-3 space-y-2 flex-grow" ondrop="drop(event)" ondragover="allowDrop(event)" ondragenter="dragEnter(event)" ondragleave="dragLeave(event)">
+            <div class="semester-list p-3 space-y-2 flex-grow relative" ondrop="drop(event)" ondragover="allowDrop(event)" ondragenter="dragEnter(event)" ondragleave="dragLeave(event)">
                 <!-- Course Cards go here -->
             </div>
             
@@ -181,45 +187,46 @@
 
     <script>
         // --- DATA ---
+        
         const generalistSemestersBlueprint = {
             1: [
-                {code: "MK06", name: "Dasar Pemrograman*", sks: 3},
-                {code: "MK07", name: "Algoritma & Logika", sks: 2},
-                {code: "MK04", name: "Kalkulus", sks: 3},
-                {code: "MK05", name: "Pengantar Informatika", sks: 2},
-                {code: "MK01", name: "Pendidikan Pancasila", sks: 2},
-                {code: "MK02", name: "Pendidikan Agama", sks: 3},
-                {code: "MK03", name: "Bahasa Inggris", sks: 2},
-                {code: "MK08", name: "Kom. Profesional", sks: 2}
+                {code: "MK06", name: "Dasar Pemrograman*", sks: 3, priority: "core"},
+                {code: "MK07", name: "Algoritma & Logika", sks: 2, priority: "core"},
+                {code: "MK04", name: "Kalkulus", sks: 3, priority: "core"},
+                {code: "MK05", name: "Pengantar Informatika", sks: 2, priority: "standard"},
+                {code: "MK01", name: "Pendidikan Pancasila", sks: 2, priority: "standard"},
+                {code: "MK02", name: "Pendidikan Agama", sks: 3, priority: "standard"},
+                {code: "MK03", name: "Bahasa Inggris", sks: 2, priority: "support"},
+                {code: "MK08", name: "Kom. Profesional", sks: 2, priority: "support"}
             ],
             2: [
-                {code: "MK15", name: "Struktur Data & Algo*", sks: 3},
-                {code: "MK12", name: "Matematika Diskrit", sks: 3},
-                {code: "MK11", name: "Sistem Digital", sks: 2},
-                {code: "MK13", name: "Org. & Ars. Komputer", sks: 3},
-                {code: "MK14", name: "Sistem Operasi*", sks: 3},
-                {code: "MK16", name: "Literasi Digital", sks: 2},
-                {code: "MK10", name: "Bahasa Indonesia", sks: 2},
-                {code: "MK09", name: "Kewarganegaraan", sks: 2}
+                {code: "MK15", name: "Struktur Data & Algo*", sks: 3, priority: "core"},
+                {code: "MK12", name: "Matematika Diskrit", sks: 3, priority: "core"},
+                {code: "MK11", name: "Sistem Digital", sks: 2, priority: "core"},
+                {code: "MK13", name: "Org. & Ars. Komputer", sks: 3, priority: "core"},
+                {code: "MK14", name: "Sistem Operasi*", sks: 3, priority: "core"},
+                {code: "MK16", name: "Literasi Digital", sks: 2, priority: "support"},
+                {code: "MK10", name: "Bahasa Indonesia", sks: 2, priority: "support"},
+                {code: "MK09", name: "Kewarganegaraan", sks: 2, priority: "support"}
             ],
             3: [
-                {code: "MK20", name: "Basis Data*", sks: 3},
-                {code: "MK21", name: "Jaringan Komputer*", sks: 3},
-                {code: "MK27", name: "PBO*", sks: 3},
-                {code: "MK24", name: "IMK", sks: 2},
-                {code: "MK22", name: "Strategi Algoritma*", sks: 3},
-                {code: "MK17", name: "Aljabar Linier", sks: 3},
-                {code: "MK19", name: "Sistem Informasi", sks: 2},
-                {code: "MK18", name: "Etika & Keberlanjutan", sks: 2}
+                {code: "MK20", name: "Basis Data*", sks: 3, priority: "core"},
+                {code: "MK21", name: "Jaringan Komputer*", sks: 3, priority: "core"},
+                {code: "MK27", name: "PBO*", sks: 3, priority: "core"},
+                {code: "MK22", name: "Strategi Algoritma*", sks: 3, priority: "core"},
+                {code: "MK17", name: "Aljabar Linier", sks: 3, priority: "core"},
+                {code: "MK24", name: "IMK", sks: 2, priority: "support"},
+                {code: "MK19", name: "Sistem Informasi", sks: 2, priority: "support"},
+                {code: "MK18", name: "Etika & Keberlanjutan", sks: 2, priority: "support"}
             ],
             4: [
-                {code: "MK23", name: "RPL*", sks: 3},
-                {code: "MK32", name: "Probstat", sks: 3},
-                {code: "MK31", name: "Pemrograman Web*", sks: 3},
-                {code: "MK30", name: "Kecerdasan Buatan", sks: 3},
-                {code: "MK25", name: "APSI", sks: 3},
-                {code: "MK29", name: "Pemrog. Jaringan*", sks: 3},
-                {code: "MK26", name: "Sis. Paralel", sks: 2}
+                {code: "MK23", name: "RPL*", sks: 3, priority: "core"},
+                {code: "MK32", name: "Probstat", sks: 3, priority: "core"},
+                {code: "MK31", name: "Pemrograman Web*", sks: 3, priority: "core"},
+                {code: "MK30", name: "Kecerdasan Buatan", sks: 3, priority: "core"},
+                {code: "MK25", name: "APSI", sks: 3, priority: "standard"},
+                {code: "MK29", name: "Pemrog. Jaringan*", sks: 3, priority: "standard"},
+                {code: "MK26", name: "Sis. Paralel", sks: 2, priority: "standard"}
             ]
         };
 
@@ -229,31 +236,31 @@
                 color: "text-blue-800",
                 desc: "Fokus: Data, ML, Vision.",
                 sem5: [
-                    {code: "MK35", name: "Machine Learning", sks: 3},
-                    {code: "MK28", name: "Metode Numerik*", sks: 3},
-                    {code: "MK36", name: "Proyek PL*", sks: 3},
-                    {code: "MK37", name: "Proposal TA", sks: 2},
-                    {code: "MKP", name: "Data Mining", sks: 3},
-                    {code: "MKP", name: "Big Data", sks: 3},
-                    {code: "MK33", name: "IoT", sks: 3}
+                    {code: "MK35", name: "Machine Learning", sks: 3, priority: "core"},
+                    {code: "MK28", name: "Metode Numerik*", sks: 3, priority: "core"},
+                    {code: "MK36", name: "Proyek PL*", sks: 3, priority: "core"},
+                    {code: "MK37", name: "Proposal TA", sks: 2, priority: "core"},
+                    {code: "MKP", name: "Data Mining", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Big Data", sks: 3, priority: "standard"},
+                    {code: "MK33", name: "IoT", sks: 3, priority: "standard"}
                 ],
                 sem6: [
-                    {code: "MK38", name: "Comp. Vision*", sks: 3},
-                    {code: "MK43", name: "NLP", sks: 3},
-                    {code: "MK44", name: "Kerja Praktik", sks: 2},
-                    {code: "MKP", name: "Deep Learning", sks: 3},
-                    {code: "MKP", name: "AI Ethics", sks: 2},
-                    {code: "MKP", name: "Pilihan Lintas KK", sks: 3},
-                    {code: "MK42", name: "Keamanan Info*", sks: 2}
+                    {code: "MK38", name: "Comp. Vision*", sks: 3, priority: "core"},
+                    {code: "MK43", name: "NLP", sks: 3, priority: "core"},
+                    {code: "MK44", name: "Kerja Praktik", sks: 2, priority: "core"},
+                    {code: "MKP", name: "Deep Learning", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "AI Ethics", sks: 2, priority: "standard"},
+                    {code: "MKP", name: "Pilihan Lintas KK", sks: 3, priority: "standard"},
+                    {code: "MK42", name: "Keamanan Info*", sks: 2, priority: "standard"}
                 ],
                 sem7: [
-                    {code: "MK48", name: "TA 1", sks: 2},
-                    {code: "MK45", name: "Teknopreneur [K]", sks: 3},
-                    {code: "MK47", name: "Uji PL", sks: 3},
-                    {code: "MK42", name: "Keamanan Info", sks: 3},
-                    {code: "MKP", name: "Health Info", sks: 3},
-                    {code: "MKP", name: "Reinforcement L.", sks: 3},
-                    {code: "MKP", name: "Quantum/Bebas", sks: 5}
+                    {code: "MK48", name: "TA 1", sks: 2, priority: "core"},
+                    {code: "MK45", name: "Teknopreneur [K]", sks: 3, priority: "standard"},
+                    {code: "MK47", name: "Uji PL", sks: 3, priority: "standard"},
+                    {code: "MK42", name: "Keamanan Info", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Health Info", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Reinforcement L.", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Quantum/Bebas", sks: 5, priority: "standard"}
                 ]
             },
             rpl: {
@@ -261,30 +268,30 @@
                 color: "text-orange-800",
                 desc: "Fokus: Apps, Architecture, UX.",
                 sem5: [
-                    {code: "MK36", name: "Proyek PL*", sks: 3},
-                    {code: "MKP", name: "UX/UI Design", sks: 3},
-                    {code: "MKP", name: "Secure SE", sks: 3},
-                    {code: "MKP", name: "Web Lanjut", sks: 3},
-                    {code: "MK28", name: "Metode Numerik*", sks: 3},
-                    {code: "MK37", name: "Proposal TA", sks: 2},
-                    {code: "MK33", name: "IoT", sks: 3}
+                    {code: "MK36", name: "Proyek PL*", sks: 3, priority: "core"},
+                    {code: "MKP", name: "UX/UI Design", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Secure SE", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Web Lanjut", sks: 3, priority: "standard"},
+                    {code: "MK28", name: "Metode Numerik*", sks: 3, priority: "standard"},
+                    {code: "MK37", name: "Proposal TA", sks: 2, priority: "core"},
+                    {code: "MK33", name: "IoT", sks: 3, priority: "standard"}
                 ],
                 sem6: [
-                    {code: "MK39", name: "Pemrog. Mobile*", sks: 3},
-                    {code: "MKP", name: "Microservices", sks: 3},
-                    {code: "MKP", name: "Game Dev", sks: 3},
-                    {code: "MK44", name: "Kerja Praktik", sks: 2},
-                    {code: "MK41", name: "Sis. Enterprise", sks: 3},
-                    {code: "MKP", name: "Pil. Lintas KK", sks: 4}
+                    {code: "MK39", name: "Pemrog. Mobile*", sks: 3, priority: "core"},
+                    {code: "MKP", name: "Microservices", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Game Dev", sks: 3, priority: "standard"},
+                    {code: "MK44", name: "Kerja Praktik", sks: 2, priority: "core"},
+                    {code: "MK41", name: "Sis. Enterprise", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Lintas KK", sks: 4, priority: "standard"}
                 ],
                 sem7: [
-                    {code: "MK48", name: "TA 1", sks: 2},
-                    {code: "MK45", name: "Teknopreneur [K]", sks: 3},
-                    {code: "MK47", name: "Uji PL", sks: 3},
-                    {code: "MK42", name: "Keamanan Info", sks: 3},
-                    {code: "MKP", name: "DevOps", sks: 3},
-                    {code: "MKP", name: "Soft. Arch", sks: 3},
-                    {code: "MKP", name: "Pil. Bebas", sks: 5}
+                    {code: "MK48", name: "TA 1", sks: 2, priority: "core"},
+                    {code: "MK45", name: "Teknopreneur [K]", sks: 3, priority: "standard"},
+                    {code: "MK47", name: "Uji PL", sks: 3, priority: "standard"},
+                    {code: "MK42", name: "Keamanan Info", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "DevOps", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Soft. Arch", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Bebas", sks: 5, priority: "standard"}
                 ]
             },
             net: {
@@ -292,30 +299,30 @@
                 color: "text-emerald-800",
                 desc: "Fokus: Infra, Security, IoT.",
                 sem5: [
-                    {code: "MK33", name: "IoT", sks: 3},
-                    {code: "MK34", name: "Manajemen Jar.*", sks: 3},
-                    {code: "MKP", name: "Embedded Sys", sks: 3},
-                    {code: "MKP", name: "Ethical Hack", sks: 3},
-                    {code: "MK36", name: "Proyek PL*", sks: 3},
-                    {code: "MK28", name: "Metode Numerik*", sks: 3},
-                    {code: "MK37", name: "Proposal TA", sks: 2}
+                    {code: "MK33", name: "IoT", sks: 3, priority: "core"},
+                    {code: "MK34", name: "Manajemen Jar.*", sks: 3, priority: "core"},
+                    {code: "MKP", name: "Embedded Sys", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Ethical Hack", sks: 3, priority: "standard"},
+                    {code: "MK36", name: "Proyek PL*", sks: 3, priority: "core"},
+                    {code: "MK28", name: "Metode Numerik*", sks: 3, priority: "standard"},
+                    {code: "MK37", name: "Proposal TA", sks: 2, priority: "core"}
                 ],
                 sem6: [
-                    {code: "MK42", name: "Keamanan Info*", sks: 3},
-                    {code: "MKP", name: "Wireless Sensor", sks: 3},
-                    {code: "MKP", name: "Cryptography", sks: 3},
-                    {code: "MK44", name: "Kerja Praktik", sks: 2},
-                    {code: "MK39", name: "Mobile (IoT)*", sks: 3},
-                    {code: "MKP", name: "Pil. Lintas KK", sks: 3}
+                    {code: "MK42", name: "Keamanan Info*", sks: 3, priority: "core"},
+                    {code: "MKP", name: "Wireless Sensor", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Cryptography", sks: 3, priority: "standard"},
+                    {code: "MK44", name: "Kerja Praktik", sks: 2, priority: "core"},
+                    {code: "MK39", name: "Mobile (IoT)*", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Lintas KK", sks: 3, priority: "standard"}
                 ],
                 sem7: [
-                    {code: "MK48", name: "TA 1", sks: 2},
-                    {code: "MK45", name: "Teknopreneur [K]", sks: 3},
-                    {code: "MK47", name: "Uji PL", sks: 3},
-                    {code: "MKP", name: "Cloud IoT", sks: 3},
-                    {code: "MKP", name: "Blockchain", sks: 3},
-                    {code: "MKP", name: "Pil. Bebas 1", sks: 3},
-                    {code: "MKP", name: "Pil. Bebas 2", sks: 6}
+                    {code: "MK48", name: "TA 1", sks: 2, priority: "core"},
+                    {code: "MK45", name: "Teknopreneur [K]", sks: 3, priority: "standard"},
+                    {code: "MK47", name: "Uji PL", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Cloud IoT", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Blockchain", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Bebas 1", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Bebas 2", sks: 6, priority: "standard"}
                 ]
             },
             si: {
@@ -323,38 +330,38 @@
                 color: "text-purple-800",
                 desc: "Fokus: Business, GIS, Governance.",
                 sem5: [
-                    {code: "MKP", name: "Business Intel", sks: 3},
-                    {code: "MKP", name: "GIS II", sks: 3},
-                    {code: "MK36", name: "Proyek PL*", sks: 3},
-                    {code: "MK28", name: "Metode Numerik*", sks: 3},
-                    {code: "MK37", name: "Proposal TA", sks: 2},
-                    {code: "MKP", name: "E-Business", sks: 3},
-                    {code: "MK33", name: "IoT", sks: 3}
+                    {code: "MKP", name: "Business Intel", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "GIS II", sks: 3, priority: "standard"},
+                    {code: "MK36", name: "Proyek PL*", sks: 3, priority: "core"},
+                    {code: "MK28", name: "Metode Numerik*", sks: 3, priority: "standard"},
+                    {code: "MK37", name: "Proposal TA", sks: 2, priority: "core"},
+                    {code: "MKP", name: "E-Business", sks: 3, priority: "standard"},
+                    {code: "MK33", name: "IoT", sks: 3, priority: "standard"}
                 ],
                 sem6: [
-                    {code: "MK41", name: "Sis. Enterprise", sks: 3},
-                    {code: "MK40", name: "SIG", sks: 3},
-                    {code: "MKP", name: "Enterprise Arch", sks: 3},
-                    {code: "MKP", name: "Smart City", sks: 3},
-                    {code: "MK44", name: "Kerja Praktik", sks: 2},
-                    {code: "MKP", name: "Pil. Lintas KK", sks: 3}
+                    {code: "MK41", name: "Sis. Enterprise", sks: 3, priority: "core"},
+                    {code: "MK40", name: "SIG", sks: 3, priority: "core"},
+                    {code: "MKP", name: "Enterprise Arch", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Smart City", sks: 3, priority: "standard"},
+                    {code: "MK44", name: "Kerja Praktik", sks: 2, priority: "core"},
+                    {code: "MKP", name: "Pil. Lintas KK", sks: 3, priority: "standard"}
                 ],
                 sem7: [
-                    {code: "MK48", name: "TA 1", sks: 2},
-                    {code: "MK45", name: "Teknopreneur [K]", sks: 3},
-                    {code: "MK47", name: "Uji PL", sks: 3},
-                    {code: "MK42", name: "Keamanan Info", sks: 3},
-                    {code: "MKP", name: "SCM", sks: 3},
-                    {code: "MKP", name: "IT Governance", sks: 3},
-                    {code: "MKP", name: "Pil. Bebas", sks: 6}
+                    {code: "MK48", name: "TA 1", sks: 2, priority: "core"},
+                    {code: "MK45", name: "Teknopreneur [K]", sks: 3, priority: "standard"},
+                    {code: "MK47", name: "Uji PL", sks: 3, priority: "standard"},
+                    {code: "MK42", name: "Keamanan Info", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "SCM", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "IT Governance", sks: 3, priority: "standard"},
+                    {code: "MKP", name: "Pil. Bebas", sks: 6, priority: "standard"}
                 ]
             }
         };
 
         const mbkmData = [
-            {code: "MK46", name: "PMKM (Wajib)", sks: 2},
-            {code: "MK45", name: "Teknopreneur (Konversi)", sks: 3},
-            {code: "MKP", name: "Pilihan Bebas (Ops)", sks: 3}
+            {code: "MK46", name: "PMKM (Wajib)", sks: 2, priority: "core"},
+            {code: "MK45", name: "Teknopreneur (Konversi)", sks: 3, priority: "standard"},
+            {code: "MKP", name: "Pilihan Bebas (Ops)", sks: 3, priority: "standard"}
         ];
 
         // --- STATE ---
@@ -391,7 +398,7 @@
             currentPlan[5] = JSON.parse(JSON.stringify(track.sem5));
             currentPlan[6] = JSON.parse(JSON.stringify(track.sem6));
             currentPlan[7] = JSON.parse(JSON.stringify(track.sem7));
-            currentPlan[8] = [{code: "MK49", name: "TA 2 (Sidang)", sks: 4}];
+            currentPlan[8] = [{code: "MK49", name: "TA 2 (Sidang)", sks: 4, priority: "core"}];
         }
 
         function renderSem(semId, containerId) {
@@ -451,21 +458,24 @@
                 semesterStats[semId].gpa = val;
                 gpaValEl.textContent = val.toFixed(2);
                 
-                // Update display of next limit immediately
                 if(semId < 8) nextMaxEl.textContent = calculateMaxSKS(val);
-
-                // Trigger re-render of NEXT semester (to show overload warning)
-                // We re-render everything to be safe and simple
-                // Debounce slighty could be good but for now direct call
             });
             gpaSlider.addEventListener('change', () => {
-                renderAll(); // Re-render all to propagate red status to next semester
+                renderAll(); 
             });
 
             // Populate List
             const listContainer = clone.querySelector('.semester-list');
-            listContainer.id = `list-sem-${semId}`; // For drag logic ref
-            listContainer.setAttribute('ondrop', `drop(event, ${semId})`); // Update drop target ID
+            listContainer.id = `list-sem-${semId}`; 
+            
+            // --- NEW: Parity Enforcement Logic ---
+            const isOddSem = semId % 2 !== 0;
+            const parityClass = isOddSem ? 'odd-semester' : 'even-semester';
+            listContainer.classList.add(parityClass);
+            listContainer.dataset.parity = isOddSem ? 'odd' : 'even';
+            // -------------------------------------
+
+            listContainer.setAttribute('ondrop', `drop(event, ${semId})`);
 
             courses.forEach((c, idx) => {
                 const el = document.createElement('div');
@@ -473,12 +483,24 @@
                 el.setAttribute('draggable', 'true');
                 el.setAttribute('ondragstart', `drag(event, ${semId}, ${idx})`);
                 
-                // Styling for special items
+                // Styling
                 if(c.name.includes('KONVERSI')) el.classList.add('bg-green-50', 'border-green-200');
+                
+                let badgeHTML = '';
+                if(c.priority === 'core') {
+                    el.classList.add('border-l-4', 'border-l-blue-500');
+                    badgeHTML = '<span class="text-[9px] bg-blue-100 text-blue-700 px-1 rounded ml-1 border border-blue-200" title="Pondasi Wajib">PONDASI</span>';
+                } else if(c.priority === 'support') {
+                    el.classList.add('bg-stone-50', 'opacity-90');
+                    badgeHTML = '<span class="text-[9px] bg-stone-200 text-stone-600 px-1 rounded ml-1 border border-stone-300" title="Bisa Ditunda">TUNDA?</span>';
+                }
 
                 el.innerHTML = `
                     <div class="overflow-hidden">
-                        <div class="text-[10px] text-stone-400 font-mono">${c.code}</div>
+                        <div class="flex items-center gap-1">
+                            <div class="text-[10px] text-stone-400 font-mono">${c.code}</div>
+                            ${badgeHTML}
+                        </div>
                         <div class="text-xs font-bold text-stone-700 truncate w-32" title="${c.name}">${c.name}</div>
                     </div>
                     <div class="text-xs font-bold bg-stone-100 text-stone-600 px-1.5 py-0.5 rounded border border-stone-200 ml-2">${c.sks}</div>
@@ -491,18 +513,14 @@
         }
 
         function renderAll() {
-            // Render 1-4
             renderSem(1, 'container-sem-1');
             renderSem(2, 'container-sem-2');
             renderSem(3, 'container-sem-3');
             renderSem(4, 'container-sem-4');
 
-            // Render 5-8 (Inside Specialist Section)
             const track = tracksBlueprint[currentTrack];
             const contentDiv = document.getElementById('specialist-content');
             
-            // We recreate the grid structure for 5-8 inside the content div
-            // This is a bit brute force but keeps logic simple
             contentDiv.innerHTML = `
                 <div class="mb-4">
                     <h3 class="text-xl font-bold ${track.color}">${track.name}</h3>
@@ -510,7 +528,6 @@
                 </div>
                 <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-4 gap-6">
                     <div id="container-sem-5"></div>
-                    <!-- MBKM Slot Visual -->
                     <div class="flex flex-col gap-4">
                         <div class="bg-gradient-to-br from-green-50 to-emerald-100 rounded-xl border border-green-200 p-3 shadow-sm h-auto relative">
                              <div class="absolute top-0 right-0 bg-green-200 text-green-800 text-[9px] font-bold px-2 py-1 rounded-bl">LIBURAN</div>
@@ -518,7 +535,10 @@
                             <div class="space-y-2">
                                 ${mbkmData.map(c => `
                                     <div class="bg-white/60 p-2 rounded border border-green-100 flex justify-between items-center">
-                                        <span class="text-[10px] font-bold text-green-800">${c.name}</span>
+                                        <div class="flex flex-col">
+                                            <span class="text-[10px] font-bold text-green-800">${c.name}</span>
+                                            <span class="text-[8px] text-green-600">${c.priority === 'core' ? 'Wajib' : 'Opsional'}</span>
+                                        </div>
                                         <span class="text-[9px] bg-green-200 text-green-800 px-1 rounded">${c.sks}</span>
                                     </div>
                                 `).join('')}
@@ -546,30 +566,85 @@
             renderAll();
         }
 
-        // --- DRAG & DROP ---
+        // --- DRAG & DROP WITH PARITY CHECK ---
         let draggedItem = null;
 
         function drag(ev, semId, idx) {
             draggedItem = { semId, idx };
             ev.dataTransfer.effectAllowed = "move";
             ev.target.style.opacity = '0.4';
+            
+            // Set global parity state for visual feedback
+            const isOddSource = semId % 2 !== 0;
+            document.body.classList.add(isOddSource ? 'dragging-odd' : 'dragging-even');
+            
+            // Visual Update: Dim invalid targets
+            document.querySelectorAll('.semester-list').forEach(el => {
+                const targetIsOdd = el.dataset.parity === 'odd';
+                if(isOddSource !== targetIsOdd) {
+                    el.classList.add('invalid-target');
+                } else {
+                    el.classList.add('valid-target-hint'); // Optional hint style
+                }
+            });
+        }
+
+        function dragEndCleanup() {
+            document.body.classList.remove('dragging-odd', 'dragging-even');
+            document.querySelectorAll('.semester-list').forEach(el => {
+                el.classList.remove('drag-over', 'valid-target', 'invalid-target', 'valid-target-hint');
+            });
+            if(draggedItem) {
+                // Reset opacity if drag failed/cancelled
+                // Ideally found by element ref, but re-render fixes it anyway
+            }
+            draggedItem = null;
+        }
+
+        function allowDrop(ev) { 
+            ev.preventDefault(); 
         }
 
-        function allowDrop(ev) { ev.preventDefault(); }
         function dragEnter(ev) { 
             ev.preventDefault();
-            ev.currentTarget.classList.add('drag-over');
+            const target = ev.currentTarget;
+            
+            // Check parity match visual
+            if(!draggedItem) return;
+            const sourceParity = draggedItem.semId % 2 !== 0 ? 'odd' : 'even';
+            const targetParity = target.dataset.parity;
+            
+            if(sourceParity === targetParity) {
+                target.classList.add('valid-target');
+            }
         }
+
         function dragLeave(ev) { 
-            ev.currentTarget.classList.remove('drag-over');
+            ev.currentTarget.classList.remove('valid-target');
         }
 
         function drop(ev, targetSem) {
             ev.preventDefault();
-            document.querySelectorAll('.semester-list').forEach(el => el.classList.remove('drag-over'));
             
-            if (!draggedItem) return;
+            if (!draggedItem) {
+                dragEndCleanup();
+                return;
+            }
+
             const { semId, idx } = draggedItem;
+            
+            // --- VALIDATION: PARITY CHECK ---
+            const sourceParity = semId % 2;
+            const targetParity = targetSem % 2;
+
+            if (sourceParity !== targetParity) {
+                // Invalid Drop
+                // alert("Mata kuliah Ganjil hanya bisa diambil di Semester Ganjil, dan Genap di Genap.");
+                dragEndCleanup();
+                renderAll(); // Reset visual state
+                return;
+            }
+            // --------------------------------
 
             if (semId !== targetSem) {
                 // Move logic
@@ -577,12 +652,16 @@
                 currentPlan[semId].splice(idx, 1);
                 currentPlan[targetSem].push(course);
                 
-                renderAll(); // Re-calc status
+                dragEndCleanup();
+                renderAll(); 
             } else {
-                renderAll(); // Just reset opacity
+                dragEndCleanup();
+                renderAll(); 
             }
-            draggedItem = null;
         }
+        
+        // Add global dragend listener to ensure cleanup happens even if dropped outside
+        document.addEventListener('dragend', dragEndCleanup);
 
         // --- CHARTS ---
         let sksChart = null;
