import streamlit as st
import math

st.title("🧮 Simple Calculator")

operation = st.selectbox("Choose Operation", ["Addition", "Subtraction", "Multiplication", "Division", "Logarithm"])

if operation != "Logarithm":
    num1 = st.number_input("Enter first number", value=0.0)
    num2 = st.number_input("Enter second number", value=0.0)

    if operation == "Addition":
        result = num1 + num2
    elif operation == "Subtraction":
        result = num1 - num2
    elif operation == "Multiplication":
        result = num1 * num2
    elif operation == "Division":
        if num2 != 0:
            result = num1 / num2
        else:
            result = "Error: Division by zero"
else:
    num = st.number_input("Enter a number for log", value=1.0)
    base = st.number_input("Enter base of log", value=10.0)
    if num > 0 and base > 0 and base != 1:
        result = math.log(num, base)
    else:
        result = "Error: Invalid input for logarithm"

st.markdown(f"### Result: `{result}`")