```bash
#!/bin/bash

# ==========================================
# FilesSample.com - Shell File Sample
# ==========================================

WEBSITE="FilesSample.com"
FILE_TYPE="Shell File Sample"
VERSION="1.0"
AUTHOR="FilesSample.com"

echo "=========================================="
echo "        FILE SAMPLE INFORMATION"
echo "=========================================="

echo "Website: $WEBSITE"
echo "File Type: $FILE_TYPE"
echo "Version: $VERSION"
echo "Author: $AUTHOR"

echo ""
echo "Welcome to $WEBSITE"
echo "This is an example of a Shell script file."

# ------------------------------------------
# System Information
# ------------------------------------------

echo ""
echo "System Information"
echo "------------------------------------------"

echo "Current User: $(whoami)"
echo "Current Directory: $(pwd)"
echo "Current Date: $(date)"

# ------------------------------------------
# File Type List
# ------------------------------------------

echo ""
echo "Common File Types"
echo "------------------------------------------"

file_types=(
    "PDF"
    "DOC"
    "DOCX"
    "TXT"
    "CSV"
    "XLS"
    "XLSX"
    "PPT"
    "PPTX"
    "JPG"
    "PNG"
    "HTML"
    "CSS"
    "JavaScript"
    "Java"
    "C++"
    "Shell"
)

for file in "${file_types[@]}"
do
    echo "- $file"
done

# ------------------------------------------
# Basic Calculations
# ------------------------------------------

echo ""
echo "Basic Calculations"
echo "------------------------------------------"

NUMBER_ONE=25
NUMBER_TWO=15

ADDITION=$((NUMBER_ONE + NUMBER_TWO))
SUBTRACTION=$((NUMBER_ONE - NUMBER_TWO))
MULTIPLICATION=$((NUMBER_ONE * NUMBER_TWO))
DIVISION=$((NUMBER_ONE / NUMBER_TWO))

echo "First Number: $NUMBER_ONE"
echo "Second Number: $NUMBER_TWO"
echo "Addition: $ADDITION"
echo "Subtraction: $SUBTRACTION"
echo "Multiplication: $MULTIPLICATION"
echo "Division: $DIVISION"

# ------------------------------------------
# Check Number
# ------------------------------------------

echo ""
echo "Number Check"
echo "------------------------------------------"

if [ "$ADDITION" -gt 30 ]; then
    echo "The addition result is greater than 30."
elif [ "$ADDITION" -eq 30 ]; then
    echo "The addition result is exactly 30."
else
    echo "The addition result is less than 30."
fi

# ------------------------------------------
# Create a Sample Directory
# ------------------------------------------

SAMPLE_DIRECTORY="filesample_demo"

echo ""
echo "Directory Operation"
echo "------------------------------------------"

if [ -d "$SAMPLE_DIRECTORY" ]; then
    echo "Directory already exists: $SAMPLE_DIRECTORY"
else
    mkdir "$SAMPLE_DIRECTORY"
    echo "Directory created: $SAMPLE_DIRECTORY"
fi

# ------------------------------------------
# Create Sample Text File
# ------------------------------------------

SAMPLE_FILE="$SAMPLE_DIRECTORY/sample.txt"

echo "This is a sample file created by a Shell script." > "$SAMPLE_FILE"
echo "Website: $WEBSITE" >> "$SAMPLE_FILE"
echo "File Type: Shell File" >> "$SAMPLE_FILE"

echo "Sample file created: $SAMPLE_FILE"

# ------------------------------------------
# Function Example
# ------------------------------------------

show_message() {

    local message="$1"

    echo ""
    echo "Message"
    echo "------------------------------------------"
    echo "$message"
}

show_message "Shell scripts can automate repetitive tasks."

# ------------------------------------------
# Simple Loop
# ------------------------------------------

echo ""
echo "Counting Example"
echo "------------------------------------------"

for ((counter=1; counter<=10; counter++))
do
    echo "Processing item: $counter"
done

# ------------------------------------------
# Environment Information
# ------------------------------------------

echo ""
echo "Environment Information"
echo "------------------------------------------"

echo "Home Directory: $HOME"
echo "Shell: $SHELL"
echo "Operating System Information:"

if [ -f /etc/os-release ]; then
    cat /etc/os-release | head -n 5
else
    echo "Operating system information is not available."
fi

# ------------------------------------------
# Completion Message
# ------------------------------------------

echo ""
echo "=========================================="
echo "       SHELL SAMPLE COMPLETED"
echo "=========================================="

echo "Thank you for visiting $WEBSITE"
echo "Explore more file samples at FilesSample.com"
```