The table and the starting layout
Four-ball (sagu, 사구) is the Korean carom game played with four balls and no pockets: you score when your cue ball touches both reds. GameNow’s table is the KBF international medium size, 2540 × 1270 mm, with 65.5 mm, 255 g balls. You play the white; the yellow is your opponent’s cue ball, played by the AI in solo games and by the other side online.
Every game starts from the same layout. The two reds sit on the long centre line at the quarter points, 635 mm from each short rail. Your white starts 160 mm from the near red, just off the centre line, and the yellow sits on the centre line behind the far red, about 32 cm from the far short rail. In solo games you always break.
Scoring and your target (dama)
Each carom is worth 10. Every player picks a personal target from 10 to 500 in steps of 10 and wins on reaching it: a target of 30 means three caroms, 150 means fifteen. Solo games have separate My target and AI target boxes, so two different handicaps can play each other.
A scoring shot earns another shot; your inning ends at the first shot that does not score. A foul only costs the turn, and nothing is deducted. Online rooms seat one to four players. In a 2-vs-2 room the team target is the sum of both players’ targets, and a scoring shot passes the cue to your teammate instead of keeping it with you.
How the game judges a carom
The simulation records every ball and cushion contact during a shot, and the verdict is read from that list. The server and every screen run the same code. The rules it applies:
- Both reds must touch your cue ball during the shot, in either order. Any collision involving your cue ball counts, including a red rolling into it.
- Only your cue ball’s cushion contacts are counted, and only those made before it reaches the second red.
- Required cushions (0–3) demands that many of those cushions before the second red. Rails before first red (0–2) demands cushions before the first red, the Korean garak rule. Both stay at Any unless you change them.
- Opponent-ball foul: touching the yellow at any point in the shot is a foul, even when both reds were made. The box is ticked by default, but the rule applies only to a player whose own target is above 30, so a beginner on 30 is exempt.
Reading a miss
A miss comes with a reason. If the cue ball passed within 5 mm of the red it still needed, the message gives the gap in millimetres, and hitting the same red twice without reaching the other is named as such. Under the table, the contact list shows every contact and cushion with its time and marks the event that completed a score. Tap a line and the table returns to that instant with the ball or rail highlighted.
The opening shot
On the break, the first ball you touch must be the far red. Touching the near red or the yellow first is a foul even if both reds are made. After New game the cue already points at the centre of the far red, but that full hit at the default 45% power does not score: the cue ball reaches the far short rail and never comes back to the near red.
One route that works in this physics: turn the aim 1.7° to your right (three presses of → at 0.5° each, then two taps of ▶ at 0.1°), set follow to 0.5 or 0.6 (five or six presses of W), keep 45% power (Space shoots at the set value; on the gauge, release at 45%) and shoot. The cue ball takes the far red a little thinner than half-ball, runs to the far short rail, comes back off the long rail on the side your white started from, and meets the near red. Run through the game’s simulation, every aim from 1.6° to 1.9° scores with that spin and power, with either the Normal or the Push stroke. Without spin, the same route needs about 50–60% power.
Aiming with the path guide
The Path guide, on by default, re-runs the real simulation with your current aim, power, spin and stroke whenever one of them changes, so speed, spin and throw are already in it. On the 3D table it draws a white line from the cue ball to the first ball it will touch and a white ring where the cue ball will be at that moment: the ghost ball. It then shows 0.7 seconds of what follows, the cue ball’s path in pale yellow and the struck ball’s path in pink if it is a red, gold if it is not.
Three limits matter. The guide stops 0.7 seconds after the first contact, so it never confirms that the cue ball reaches the second red; judge that from the departure line. It also uses the stored power setting (45% at the start, then your last shot’s power, or whatever ↑ ↓ set), not the pull you are making on the gauge. And on devices that fall back to the flat 2D table, only the line and the ring are drawn.
For fine control, the ◀ ▶ buttons turn the aim 0.1° per tap and speed up to 0.5° steps when held. On a keyboard, ← → turn 0.5° (0.05° with Shift), ↑ ↓ change power by 5%, W A S D move the tip by 0.1, Space shoots and V switches to Cue view, where dragging sideways turns the cue.
Choosing power
Full power sends the cue ball off at 5.2 m/s, and the gauge is curved, so the upper half adds speed quickly. A centre-ball shot sent straight up and down the table with nothing in its way travels roughly:
- 20%: 1.6 m, less than one table length
- 30%: 3.2 m
- 45%, the starting value: 6.3 m
- 60%: 9.3 m
- 100%: 14.9 m
Speed at the cushion
The table is 2.54 m long, so the default 45% already covers about two and a half lengths. Cushions also take more out of fast balls: a rail gives back about 90% of a slow ball’s speed across it, but only 74% on hard hits. Pick the lowest power that completes the route.
Spin: follow, draw and side
Open the spin pad from the ball icon at the bottom left of the table. Up is follow, down is draw, left and right add side spin. The rim of the pad is the edge of the usable tip area, about half the ball’s radius from centre, and the simulation has no miscues, so the rim is safe to use.
Balls slide first, and cloth friction then turns sliding into natural roll, so spin put on at the cue fades with distance. On the Billiards basics lesson layout, with the red 635 mm away, a full hit with 0.6 draw brings the cue ball back at 60% power; at 30% the draw has become forward roll by the time it arrives, and the cue ball follows the red instead. On a half-ball hit the red leaves 28–30° from your aim line whatever spin you use, and the cue ball starts along the tangent line, about 58° the other way. Follow then bends it toward the aim line; draw, if it survives to contact, bends it wider.
Side spin is what changes cushion angles. A ball rolling into a long rail at 45° comes off at about 43° from the perpendicular with no side. With 0.6 running side, meaning side spin on the side the ball is heading along the rail (right spin when it is heading right), it comes off at about 47° at 30% power and 51–52° at 50–80%; the same amount of reverse side closes it to about 40–41°. Follow or draw alone moved that rebound by about 2° or less.
The three strokes in the spin panel change how much spin carries. Snap keeps about 22% more draw and 15% less follow, and adds 5% speed. Push keeps about 18% more follow and 15% less draw, and gives up 4% speed. Normal is the baseline.
Cushion-first shots
When a red is blocked, or Rails before first red asks for a cushion first, aim at the red’s mirror image: a point as far behind the cushion as the red is in front of it. The game’s AI starts its rail-first shots from the same mirror points, then tests small changes of aim, power and side through the physics before choosing one. Because a plain rolling ball comes off a little closer to the perpendicular than it went in (43° for 45°), a pure mirror aim tends to land short; a touch of running side, or aiming slightly farther along the rail, makes up the difference.
Common beginner mistakes
- Leaving power at 45% for every shot. Extra distance gives the cue ball more chances to touch the yellow.
- Using draw on slow, long shots. Spin fades with distance and may be gone before contact.
- Reading the guide past its end. It shows the first contact and 0.7 seconds after it, not the second red.
- Breaking at the near red or the yellow. The far red must be first.
- Reaching for follow or draw to change a rail angle. They barely move it; side spin does.
- Raising your target above 30 and forgetting the yellow. From 40 up, touching it is a foul if the box is ticked.
How three-cushion differs
Three-cushion uses three balls: your white, the yellow and one red, and both of the other balls are your object balls. A point needs the cue ball to touch both and to make at least three cushion contacts before it touches the second; cushions before the first ball count. Each point is worth 1 rather than 10, so the target list reads in points, and a 30 setting means 3 points.
At the start the white and yellow sit 160 mm apart at one quarter point and the red sits at the other, and the break must touch the red first. There is no opponent-ball foul, since hitting the yellow is part of every point, and the Required cushions and Rails before first red options are hidden.
Practice tools
Solo practice removes the opponent, and Retry this position restores the layout and score from before your last shot. Compare on the same layout, available after any shot, re-runs your last shot with a different power, side or follow/draw value (one at a time by default), draws both cue-ball paths, solid for the original and dashed for the change, on a shared time slider, and lists both verdicts. The Billiards basics lesson varies thickness (5–100%), tip position and power (30, 60 or 90%) on a fixed layout.
What the AI levels change
In four-ball and three-cushion the AI’s level sets its pace, not its aim. It searches real shots through the same physics, then decides on each shot whether to go for the point, so that it finishes its own target in about 30 innings on Normal, 43 on Easy and 21 on Hard. Otherwise it plays its best non-scoring shot, usually one red with the cue ball finishing near the other. Its scoring rate follows its own progress, not your score: on Normal with a target of 30 it starts out scoring on about 9% of its shots.