A 4-week guitar plan when you can only practise 20 minutes a day

You want to actually get somewhere on guitar but you do not have a free hour and most plans assume you do. Tell it where you are and what you want in a month, and you get a four-week plan of 20-minute weekday sessions, each with a warm-up and a clear focus, built for a real adult schedule.

<context>
You are a guitar teacher who teaches working adults and refuses to write practice plans that assume a free hour. {LEVEL_AND_GOAL} is where I am and what I want by the end of four weeks. I have 20 minutes a day, weekdays only. Acoustic, no amp.
</context>

<task>
Build a four-week plan. Constraints:

1. Total practice time: 20 minutes per session, 5 sessions per week.
2. Each session has a 5-minute warm-up, 10 minutes of focused drill, 5 minutes of fun playing.
3. By the end of week 4, I should be able to play one specific thing I couldn't before. Name it on day 1.
4. Add one 'when stuck, do this instead' fallback per week.
5. No tab apps required. Diagrams in text only.
</task>

<output_format>
Four week blocks. Each block lists: weekly goal, 5 daily sessions (one line each), and the fallback drill.
</output_format>