I need help with making a countdown timer using only some basic modules from python standard library. For example, instead of using sleep method, you need to implement it by yourself and to show that you can use the tools the we learned in this course.

import time

# Function to create the countdown timer

def countdown$\_$timer$($duration$)$:

# Get the current time

start$\_$time $=$ time.time$()$

# Calculate the end time

end$\_$time $=$ start$\_$time $+$ duration

# Loop until the current time reaches the end time

while time.time$()<$ end$\_$time:

# Calculate remaining time

remaining$\_$time $=$ int$($end$\_$time $-$ time.time$())$

# Display the remaining time

print$($f$"$Time left: $\{$remaining$\_$time$\}$ seconds", end$="\backslash$r$")$

# Busy$-$wait for a short duration to reduce CPU usage

busy$\_$wait$(0\mathrm{.}1)$

# Countdown is complete

print$("$

Countdown complete!"$)$

# Function to implement busy$-$wait for a given duration in seconds

def busy$\_$wait$($duration$)$:

start $=$ time.time$()$

while time.time$()-$ start $<$ duration:

pass

# Main function to get user input and start the countdown

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

# Get the countdown duration from the user

duration $=$ int$($input$("$Enter the countdown time in seconds: $"))$

# Start the countdown timer

countdown$\_$timer$($duration$)$

please explain every step and dumb it down for someone who has no knowledge on any of this. simple terms