Atmel ATTINY13 project

So I have what I hope to be a very simple project. I have a PCB with an attiny13 microcontroller and I need it to do the following. Upon start-up the board needs to wait for 3 seconds then check for a heartbeat that happens every 750ms on a specific pin. Once it has found the pulse then it will pull an gpio pin high. If at any time the pulse is not found within a time limit then the gpio pin is brought low and another pin is brought high to sound an alarm. If the pulse returns the board will return to normal operation. The 3 second startup delay needs to be configurable The 750ms pulse time needs to be configurable The time delay that it waits before it triggers needs to be configurable This needs to be compiled with winavr or avr-gcc