Create initial readme

README.md

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-# sleepycli
+<h1 align="center"> sleepycli </h1>
+
+<p align="center">
+    <img src="https://img.shields.io/badge/go-1.26.1-00ADD8?logo=go">
+    <img src="https://github.com/TyostoKarry/sleepycli/actions/workflows/verify-pr.yml/badge.svg?event=pull_request" />
+</p>
+
+A small Go CLI for calculating sleep and wake times around 90-minute sleep cycles.
+
+`sleepycli` helps you answer questions like:
+- “If I sleep now, when should I wake up?”
+- “If I want to wake up at 07:00, when should I go to bed?”
+- “How many full sleep cycles fit between two times?”
+
+The tool supports four main modes: calculate from **now**, from a target **wake** time, from a target **sleep** time, or across a **window** of time.
+
+## Features
+
+- Calculate wake times from the current time
+- Calculate bedtimes for a target wake time
+- Calculate wake times for a target sleep time
+- Calculate full sleep cycles within a sleep window
+- Configurable fall-asleep buffer
+- Configurable minimum and maximum cycle count
+- Input validation for modes, time format, and cycle ranges
+- Custom help output
+- Bash completion script
+- Pull request CI for linting and tests
+
+## How it works
+
+The calculator uses a **90-minute sleep cycle** and adds an optional **buffer** to represent the time it takes to fall asleep.
+
+Defaults:
+- Sleep cycle: `90 minutes`
+- Buffer: `15 minutes`
+- Displayed cycles: `4` to `6`
+
+## Installation
+
+### Build from source
+
+```bash
+git clone https://github.com/TyostoKarry/sleepycli.git
+cd sleepycli
+go build -o sleepycli .
+```
+
+### Run without installing
+
+```bash
+go run . --help
+```
+
+## Usage
+
+```bash
+sleepycli [mode] [options]
+```
+
+Choose exactly **one** mode.
+
+### Modes
+
+#### `--now`
+Calculate wake times starting from the current time.
+
+```bash
+sleepycli --now
+```
+
+#### `--wake HH:MM`
+Calculate suggested bedtimes for a target wake time.
+
+```bash
+sleepycli --wake 07:00
+```
+
+#### `--sleep HH:MM`
+Calculate suggested wake times for a target sleep time.
+
+```bash
+sleepycli --sleep 22:30
+```
+
+#### `--from HH:MM --to HH:MM`
+Calculate how many complete sleep cycles fit inside a time window.
+
+```bash
+sleepycli --from 22:00 --to 07:00
+```
+
+### Options examples
+
+#### Use a custom fall-asleep buffer
+
+```bash
+sleepycli --wake 07:00 --buffer 30
+```
+
+#### Show a different cycle range
+
+```bash
+sleepycli --sleep 23:00 --cycles-min 3 --cycles-max 7
+```
+
+### Sample output
+
+#### `--wake 07:00`
+
+```text
+To wake up at 07:00:
+───────────────────
+Assuming 15 min to fall asleep
+
+  - 6 cycles, go to sleep at 21:45 (9h 00m)
+  - 5 cycles, go to sleep at 23:15 (7h 30m)
+  - 4 cycles, go to sleep at 00:45 (6h 00m)
+```
+
+#### `--from 22:00 --to 07:00`
+
+```text
+Between 22:00 and 07:00:
+───────────────────────
+Assuming 15 min to fall asleep
+
+  - 5 complete cycles (7h 30m)
+  - 75 minutes remaining
+```
+
+## Flags
+
+| Flag | Description | Default |
+|---|---|---:|
+| `-n, --now` | Calculate wake times from the current time | - |
+| `-w, --wake HH:MM` | Calculate bedtimes for a target wake time | - |
+| `-s, --sleep HH:MM` | Calculate wake times for a target sleep time | - |
+| `-f, --from HH:MM` | Start of sleep window, used with `--to` | - |
+| `-t, --to HH:MM` | End of sleep window, used with `--from` | - |
+| `-b, --buffer int` | Minutes needed to fall asleep | `15` |
+| `-m, --cycles-min int` | Minimum cycles to show | `4` |
+| `-x, --cycles-max int` | Maximum cycles to show | `6` |
+| `-g, --good-night` | Print random good night ASCII art | - |
+| `-v, --version` | Print version | - |
+| `-h, --help` | Show help | - |
+
+## Input rules
+
+- Time format is 24-hour `HH:MM`
+- Short hour values like `7:00` are accepted
+- Modes cannot be combined
+- `--from` and `--to` must be used together
+- `--now`, `--wake` and `--sleep` are mutually exclusive
+- `--cycles-min` cannot be greater than `--cycles-max`
+- Buffer and cycle values cannot be negative
+
+## Bash completion
+
+A completion script is included at:
+
+```bash
+scripts/sleepycli-completion.bash
+```
+
+To load it in your current shell:
+
+```bash
+source scripts/sleepycli-completion.bash
+```
+
+To make it persistent, add that line to your shell profile.
+
+## CI
+
+The repository includes a pull request workflow that:
+- runs `golangci-lint`
+- runs `go test ./...`
+- triggers on pull requests targeting `main`