A free practice game for the Rules of the Road (COLREGs)
SkipperCheck's Colreg Game is a fast, free, browser-based drill for the International Regulations for Preventing Collisions at Sea — the COLREGs. Each round shows a procedurally generated maritime scenario, and you decide whether your vessel is the stand-on or the give-way vessel. Instant rule-based feedback turns every round into a 10-second micro-lesson.
What you practise
The game pulls from the full set of "vessels in sight" and "restricted visibility" rules. Every scenario is rule-decidable from what the canvas shows you — vessel type, relative aspect, navigation lights, day shapes, sailing tack and visibility condition.
- Rule 12 — Sailing vessels: different tacks (port-tack vessel keeps clear of starboard-tack) and same-tack (windward keeps clear of leeward).
- Rule 13 — Overtaking: any vessel approaching from more than 22.5° abaft another vessel's beam is the overtaking vessel and must keep clear — regardless of type.
- Rule 14 — Head-on: two power-driven vessels meeting on reciprocal or near-reciprocal courses both alter to starboard.
- Rule 15 — Crossing: when two power-driven vessels cross, the vessel that has the other on her own starboard side keeps clear.
- Rule 18 — Responsibilities between vessels: the priority ladder. Not Under Command → Restricted in Ability to Manoeuvre → Constrained By Draught → Fishing → Sailing → Power-driven. The vessel lower in the ladder keeps clear.
- Rule 19 — Restricted visibility: in fog there is no stand-on vessel. Every vessel that detects another only by radar must take avoiding action in ample time.
- Rule 30 — Anchored and aground: the underway vessel keeps clear of a vessel at anchor or aground.
How the game works
- The page tells you what your own vessel is — for example, "You are a power-driven vessel making way" or "You are a sailing vessel on starboard tack".
- The canvas paints the other vessel as you would see her from your bridge — her silhouette, her navigation lights at night, her day shapes by day, her aspect (bow / beam / quarter / stern) and a wind arrow when sailing rules are in play.
- You decide: STAND-ON or GIVE-WAY. The server checks your answer against the COLREG rule that decides the scenario and shows you which rule applied plus a short explanation.
- A new scenario loads immediately so you can keep drilling. Five correct in a row earns a streak bonus; wrong answers cost points.
Who it's for
The Colreg Game is built for yacht skippers preparing for the season, sailing-school students brushing up between courses, deck cadets revising for COLREG exams, and recreational boaters who want a 30-second collision-avoidance check before leaving the marina. No prior account is required — sign in if you want your points to count toward the global SkipperCheck contest leaderboard.
Frequently asked questions
What is the difference between the stand-on and the give-way vessel?
The give-way vessel must take early and substantial action to keep out of the other vessel's way (COLREG Rule 16). The stand-on vessel maintains her course and speed (Rule 17) — unless the give-way vessel fails to act, in which case the stand-on vessel must also take avoiding action.
Which COLREG rules does the game cover?
Rule 12 (sailing vessels), Rule 13 (overtaking), Rule 14 (head-on), Rule 15 (crossing power-driven vessels), Rule 18 (responsibilities between vessel types), Rule 19 (restricted visibility — no stand-on vessel exists in fog) and Rule 30 (anchored and aground vessels).
Is there a stand-on vessel in fog?
No. Rule 19 (Conduct in Restricted Visibility) states that a vessel which detects by radar alone the presence of another shall determine if a close-quarters situation is developing and take avoiding action in ample time. Both vessels are effectively give-way; there is no stand-on vessel in fog.
Who keeps clear when a power-driven vessel meets a sailing vessel?
Under Rule 18, a power-driven vessel underway keeps out of the way of a sailing vessel. The sailing vessel is the stand-on vessel; the power-driven vessel is the give-way vessel.
Does the overtaking vessel always give way?
Yes. Rule 13 makes the overtaking vessel responsible for keeping clear regardless of type — a sailing vessel overtaking a power-driven vessel still gives way; a power-driven vessel overtaking a vessel engaged in fishing still gives way. Overtaking is defined as approaching from more than 22.5° abaft the other vessel's beam.
When two sailing vessels meet, who is the stand-on vessel?
Rule 12: if they are on different tacks, the vessel on the port tack (wind on her port side) keeps clear of the vessel on starboard tack. If they are on the same tack, the windward vessel keeps clear of the leeward vessel.
How does the Rule 18 responsibility ladder work?
From most privileged to least: Not Under Command (NUC) → Restricted in Ability to Manoeuvre (RAM) → Constrained By Draught (CBD) → Vessel engaged in Fishing → Sailing vessel → Power-driven vessel. A vessel lower in the ladder keeps out of the way of a vessel higher up.
Is the Colreg Game free?
Yes — completely free, no signup required. If you sign in with a free SkipperCheck account your points contribute to the global contest leaderboard alongside the daily quiz, maritime crossword and Liar's Dice tavern.
How is the Colreg Game different from the COLREG Bridge Simulator?
The Colreg Game is a 30-second binary-choice arcade — you decide stand-on or give-way and move on. The COLREG · AIS Bridge Simulator at /colreg-simulator is the full thing: 54 scenarios with live AIS targets, sound signals, restricted visibility, ARPA radar plotting and collision-avoidance manoeuvring. The game is the warm-up; the simulator is the workout.
