How to set up a balcony garden with only 20 square feet?

Maximise 20 sq ft with vertical shelving (3-tier stands double capacity), 5-litre hanging bags on railing hooks, and compact varieties. Prioritise cut-and-come-again crops: spinach, coriander, mint, and methi. One railing-hung 5-pocket planter grows 5 herb varieties. Indian balconies yield 1–3 kg of produce monthly this way.