FlagLine Offside Lab
FlagLine Offside Lab
FlagLine Offside Lab is an offline-first interactive offside-geometry and Laws-of-the-Game decision workbench for youth assistant-referee trainees, high-school players, parent-coaches, and new center officials who must judge the line under pressure—not reread dense IFAB PDFs on the touchline. You place attackers, the second-last defender, teammates, and the ball on a true half-pitch grid; the app draws a live offside line, grades edge cases (interfering with play, interfering with an opponent, gaining an advantage, deliberate play by a defender, goalkeeper involvement, and restart exemptions), and explains the outcome in plain English. Seeded scenario packs cover common match traps; a custom builder lets you fork any freeze-frame; an assistant-ref run-the-line guide shows shoulder position and recovery steps along the touchline. Everything persists in on-device SwiftData—no accounts, no network, no player contact data.
About FlagLine Offside Lab
FlagLine Offside Lab is an offline-first interactive offside-geometry and Laws-of-the-Game decision workbench for youth assistant-referee trainees, high-school players, parent-coaches, and new center officials who must judge the line under pressure—not reread dense IFAB PDFs on the touchline. You place attackers, the second-last defender, teammates, and the ball on a true half-pitch grid; the app draws a live offside line, grades edge cases (interfering with play, interfering with an opponent, gaining an advantage, deliberate play by a defender, goalkeeper involvement, and restart exemptions), and explains the outcome in plain English. Seeded scenario packs cover common match traps; a custom builder lets you fork any freeze-frame; an assistant-ref run-the-line guide shows shoulder position and recovery steps along the touchline. Everything persists in on-device SwiftData—no accounts, no network, no player contact data.
Screenshots
FlagLine Offside Lab on iPhone and iPad.
Highlights
Walk a short onboarding that teaches the second-…
Walk a short onboarding that teaches the second-last-defender rule with three animated half-pitch demos (basic line, same-frame attacker/defender, ball played backward), then pick your role persona (assistant-ref trainee, player, parent-coach) to bias default scenario packs.
Open the Geometry Lab: drop and drag up to 11 at…
Open the Geometry Lab: drop and drag up to 11 attackers/defenders plus the ball on a true-scale half-pitch grid, snap players to lanes, flip attack direction, and watch the offside line redraw live with distance-to-line readouts and a clear ON/OFF/WAIT verdict chip.
Inspect the Edge-Case Bench: toggle structured r…
Inspect the Edge-Case Bench: toggle structured ruling cards for interfering with play, interfering with an opponent, gaining an advantage, deliberate play (including deflections), goalkeeper hand/arm involvement, and exemptions on throw-in, corner, and goal kick—each card shows a mini diagram you can promote into the full lab.
Browse a seeded library of 50+ freeze-frame scen…
Browse a seeded library of 50+ freeze-frame scenarios tagged by topic (tight shoulder, late runner, keeper parry, defender header, free-kick wall rebound, goal-kick exit) and age band (youth through adult); fork any pack item into your own editable copy.
Run Decision Mode: reveal a frozen pitch without…
Run Decision Mode: reveal a frozen pitch without the answer, choose Onside / Offside / Play-on / Wait-and-see within a soft countdown, then unlock a plain-language rationale, the correct IFAB-aligned principle, and a one-tap ‘open in Geometry Lab’ restage of the same frame.
Build custom scenarios in the Scenario Editor: n…
Build custom scenarios in the Scenario Editor: name the frame, place players and ball, attach the intended correct call and a short coach note, save into personal packs in SwiftData, and reorder packs for self-study before a course or match weekend.
Privacy first
FlagLine Offside Lab does not collect personal data — everything stays on your device, with no third-party tracking or advertising SDKs. Read the full Privacy Policy.
Support
Questions or feedback? Visit Support or email valentinpostolach@outlook.com.