Boosters explained

The booster bar

Boosters are one-shot helpers you can use during a level. In Berth Sort they sit in a bar at the bottom of the screen (or in a side column if you play in landscape), each with a small number showing how many you own. The last button in the bar is the hint lightbulb. The bar appears from Berth Sort level 4, when the first booster unlocks. Harbor Escape has six boosters; four are used in Berth Sort and Tide Challenge, and four in Classic.

Every booster at a glance

Booster	What it does	Modes	Unlocks at
Undo	Takes back your last move.	Berth Sort, Tide, Classic	Berth level 4 / Classic level 5
Call boat	Lifts one boat of the current freighter's color straight on board.	Berth Sort, Tide	Berth level 6
Extra berth	Adds one more berth for the rest of the attempt (at most two per attempt).	Berth Sort, Tide	Berth level 8
Freeze	Stops the clock for 15 seconds.	Berth Sort, Tide, Classic	Berth level 9 / Classic level 11
Remove	Lifts any boat (except a bomb) out of the harbor.	Classic	Classic level 15
Defuse	Turns a bomb boat into an ordinary boat.	Classic	Classic level 41

Harbor Rush and Cargo Match do not use boosters.

Undo

Undo puts the last boat you sent away back where it was, together with whatever it did — un-boarding it from the freighter or un-parking it from a berth. You can use several Undos in a row to step back further. It does not give back hearts lost in a crash, and it cannot go back past a Call boat or a continue.

When to use it: right after a park you regret, especially when you realize a boat you just parked will not be needed for many freighters. Undo is cheap, so it is the right tool for small mistakes; save the bigger boosters for real dead ends.

Call boat

Call boat sends a crane to pick up one boat of the current freighter's color and put it straight on board, wherever it is on the board. The game picks the boat for you, and it prefers one that is stuck behind others while keeping the level solvable. The crane can lift a mystery boat (revealing it) and an iced boat (smashing the ice), but not a locked boat or a boat hidden in fog.

When to use it: when the last boat a freighter needs is buried deep in the harbor and digging it out would fill your berths. One Call boat there can save three or four parks. It is also a good answer to a boat frozen under several layers of ice.

Extra berth

Extra berth opens one more parking space for the rest of the attempt; you can add up to two this way. On the berth row you can see the spare slot waiting with a padlock on it.

When to use it: as a last resort when you are one park away from "No berths left". Keep in mind that stars are still judged against the level's par: if parking in the extra berth pushes your busiest moment above par, the level will only give one star. It is a booster for finishing a level, not for perfecting it.

Freeze

Freeze stops the countdown for 15 seconds. It only works while a clock is running. On Hard and Super Hard Berth Sort levels that clock decides whether you win at all; on normal levels it is the gold time, so Freeze can save your third star. In Tide Challenge it stops the tide clock, which holds back the next wave. In Classic, where every timed level fails when time runs out, it buys you thinking time.

When to use it: early in a crowded timed level, while you plan the opening, or late in a level when you know the remaining moves but need a few more seconds to make them.

Remove (Classic)

Remove lifts any boat out of the harbor, blocked or not — except bomb boats. Importantly, a removed boat does not count as a boat sailing out, so the numbers on numbered boats and bombs do not drop. That makes Remove the perfect tool when a numbered boat is about to run out because too many boats stand in its way.

Defuse (Classic)

Defuse disarms a bomb boat, which then behaves like any other boat. Use it when a bomb sits in a crowded corner and you cannot clear its neighbors before it reaches zero; every boat caught in a blast would cost you a star.

Hints

The lightbulb is not a booster you collect: you get one free hint every attempt (a second one is available after an optional ad, where ads are shown). In Berth Sort the hint is based on a solution that stays within par, so following it is also a way to learn what a good opening looks like. There is no hint button on the first tutorial levels, in Tide Challenge or in Harbor Rush.

How to get more boosters

• Unlock gifts: you get two of each booster for free when it unlocks.
• Harbor Shop: buy them with stars — Undo for 30, Freeze for 40, Call boat for 50 and Extra berth for 60 stars. You can buy up to three of each per day. Remove and Defuse are not sold.
• Win streaks: winning several Berth Sort levels in a row earns free boosters for your next level, and the reward grows with longer streaks.
• Optional ads: where ads are shown, a booster you have run out of can be refilled by watching a short ad, up to twice per level.
• Other rewards: inviting friends and the Harbor Restore side game also pay out boosters.

A sensible booster budget

Stars are the same currency you use to rebuild your harbor, so buying boosters competes with repairing buildings. A good rule of thumb: never buy boosters to rush through normal levels. Use what you get for free on normal levels, and spend stars only on the Hard and Super Hard levels — they pay double and triple stars, so a booster spent there often earns itself back.