diff --git a/LICENCE.txt b/LICENCE.txt
deleted file mode 100644
index a21706f..0000000
--- a/LICENCE.txt
+++ /dev/null
@@ -1,21 +0,0 @@
-MIT License
-
-Copyright (c) 2024 Marcel Pöppe
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
diff --git a/README.md b/README.md
index 7f36f9a..ba850d4 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,8 @@ ToDo
 4. Push your branch: `git push origin featurename`
 5. Create a pull request
 # Licence
-This project is licensed under the [MIT License](https://github.com/Spaceholder-Programming/Operations-Research-Tool?tab=MIT-1-ov-file).
+For further information, please check out the [LICENSE](https://github.com/Spaceholder-Programming/Operations-Research-Tool/blob/main/LICENCE.txt).
+=======
 # Contact
 If you have the desire to contact the team behind this project, use the contact details on our GitHub accounts:
 + [bRNS98](https://github.com/bRNS98)
diff --git a/src/app/favicon.ico b/src/app/favicon.ico
index 718d6fe..959cf14 100644
Binary files a/src/app/favicon.ico and b/src/app/favicon.ico differ
diff --git a/src/app/layout.tsx b/src/app/layout.tsx
index 2d84ce5..db2d1f3 100644
--- a/src/app/layout.tsx
+++ b/src/app/layout.tsx
@@ -15,8 +15,8 @@ const geistMono = localFont({
 });
 
 export const metadata: Metadata = {
-  title: "Create Next App",
-  description: "Generated by create next app",
+  title: "OR-Tool by Spaceholder Programming",
+  description: "OR-Tool by Spaceholder Programming",
 };
 
 export default function RootLayout({
diff --git a/src/app/page.tsx b/src/app/page.tsx
index 9f1d499..dda578a 100644
--- a/src/app/page.tsx
+++ b/src/app/page.tsx
@@ -19,19 +19,19 @@ export default function Home() {
       </header>
       <Box
         title={"Objective"}
-        placeholder={"Objective"}
+        placeholder={"Insert your objective here. One objective is allowed. Use one line for it (no \"return\"!) Allowed symbols are 0-9, a-z, A-Z and <>=.\nExample:\nx + y\n-786433 x1 + 655361 x2"}
         id="objective"/>
       <Box
         title={"Subject"}
-        placeholder={"Subject"}
+        placeholder={"Insert your subject here. One per line (divide by 'return' button). Allowed symbols are 0-9, a-z, A-Z and <>=.\nExample:\n+1 x + 2 y <= 15\n524321 x14 + 524305 x15 <= 4194303.5"}
         id="subject"/>
       <Box
         title={"Bounds"}
-        placeholder={"Bounds"}
+        placeholder={"Insert your bounds here. One per line (divide by 'return' button). Allowed symbols are 0-9, a-z, A-Z and <>=.\nExample:\nx >= 0\nx > 0\n0 <= x1 <= 1"}
         id="bounds"/>
       <Box
         title={"Variables"}
-        placeholder={"Your Variables here"}
+        placeholder={"List all your variables. One per line (divide by 'return' button). Allowed symbols are a-z, A-Z.\nExample:\nx\ny"}
         id="vars" />
       <Button
         title={"Calculate"}
@@ -47,7 +47,7 @@ export default function Home() {
       <br></br>
       <Output
         id="out"
-        text={"Ergebnis"}/>
+        text={"Input a problem and an action button to display output..."}/>
       {/* <Popup_Button
         title="Popup"
         className="button"
diff --git a/src/app/scripts.ts b/src/app/scripts.ts
index f1da568..eb20879 100644
--- a/src/app/scripts.ts
+++ b/src/app/scripts.ts
@@ -46,6 +46,52 @@ function walltimeStart() {
   return Date.now();
 }
 
+function isInputValidRegex(obj: string | undefined, subj: string | undefined, bounds: string | undefined, vars: string | undefined): boolean {
+  customLog("Staring input checks...");
+  
+  // standard case: input is undefined - invalid
+  if (obj === undefined || obj === null || subj === undefined || subj === null || bounds === undefined || bounds === null || vars === undefined || vars === null) { 
+    customLog("Error: Function isInputValidRegex received undefined or null input.");
+    return false;
+  }
+
+  // RegEx check for objective
+  let regex = /^[ (\n)]*[\+-]? *((\d+(.\d+)? )?[a-zA-Z][a-zA-Z0-9]*)( *[\+-] *((\d+(.\d+)? )?[a-zA-Z][a-zA-Z0-9]*))*[ (\n)]*$/g;
+  let isValid = regex.test(obj);
+  if (!isValid) {
+    customLog("Error: Invalid or missing character in object box.");
+      return false;
+  }
+
+  // RegEx check for subject
+  regex = /^([ (\n)]*[\+-]* *(\d+(.\d+)? )?[a-zA-Z][a-zA-Z0-9]*( *[\+-] *(\d+(.\d+)? )?[a-zA-Z][a-zA-Z0-9]*)* *((<=?)|(>=?)|=) *[\+-]? *\d+(.\d+)?[ (\n)]*)+$/g;
+  isValid = regex.test(subj);
+  if (!isValid) {
+    customLog("Error: Invalid or missing character in subject box.");
+      return false;
+  }
+
+// RegEx check for subject
+regex = /[ (\n)]*(([a-zA-Z][a-zA-Z0-9]* *((<=?)|(>=?)|=) *\d(.\d+)?)|((\d(.\d+)?) *<=? *[a-zA-Z][a-zA-Z0-9]* *<= *(\d(.\d+)?)))[ (\n)]*/g;
+isValid = regex.test(bounds);
+if (!isValid) {
+  customLog("Error: Invalid or missing character in bounds box.");
+    return false;
+}
+
+  // RegEx check for variables
+  regex = /^ *([a-zA-Z][a-zA-Z0-9]*(\n)* *)+$/g;
+  isValid = regex.test(vars);
+  if (!isValid) {
+    customLog("Error: Invalid or missing  character in variables box.");
+    return false;
+  }
+
+  customLog("All input checks successful.");
+  customLog("");
+  return true;
+}
+
 function isInputFilled(obj: string | undefined, subj: string | undefined, bounds: string | undefined, vars: string | undefined) {
   if (obj == "" || obj == null || obj == undefined) {
     customLog("Error: Empty input field.");
@@ -148,6 +194,9 @@ export function calculate_click() {
   // catch error: empty input field(s)
   if (!isInputFilled(objective, subject, bounds, variables)) return;
 
+  // catch error: variables field has invalid characters
+  if (!isInputValidRegex(objective, subject, bounds, variables)) return;
+
   let wholeText: string = "Maximize\n obj: " + objective
                         + "\nSubject To \n" + subject 
                         + "\nBounds \n" + bounds