How Projectile Physics Works in Collection Games

Most collection games ask you to decide and execute continuously. A launch game asks you to decide once and then removes your input entirely. That is unusual for an arcade game and it works for reasons worth understanding.

The shape of a launch game

Gem Cannon Challenge runs the following loop:

1. Adjust the cannon's angle, between 5 and 85 degrees.
2. Hold to charge power, between 340 and 960.
3. Release to fire.
4. Watch. You have no further input.
5. The collector follows a ballistic arc, bouncing off walls and floor up to three times, sweeping every gem it passes within about fifteen pixels of.
6. The shot ends; you get another until the stage clears or you run out.

The physics are ordinary: gravity of 1,150 applied each step, position integrated from velocity, restitution of around 0.6 to 0.78 on bounces depending on the surface. Nothing exotic.

What is unusual is the removal of execution. There is no dexterity component at all — a player with perfect reactions and a player with none will get identical results from identical inputs. The entire game is the decision.

Why the arc is drawn for you

The natural instinct is that hiding the trajectory would make the game harder and therefore better. It is worth explaining why that is wrong.

Without a predicted arc, the skill being tested is estimating a parabola by eye. That is a real skill, it improves slowly, and it is not interesting. Every shot becomes a guess with a correction afterwards, and the game becomes trial and error with a shot limit.

With the arc drawn — updating live as you adjust angle and power — the question changes completely. It becomes: of all the lines available to me, which one sweeps two clusters instead of one?

That is a geometry problem with a right answer, and finding it is genuinely satisfying in a way that estimating is not. You are no longer asking whether you can hit the thing; you are asking which of several achievable shots is best.

The arc is generated by the same integration that flies the shot, so it never lies. That matters: a predicted path that is approximate would be worse than none at all, because it would teach the player to distrust the one piece of information the game gives them.

Bounces as a budget

Three bounces per shot is a design decision doing several jobs.

It turns walls into routes. Without bounces, a cluster tucked into a corner behind an obstacle is unreachable. With them, the wall is a way in — and finding that line is one of the better moments the game offers.

It extends shot lifetime meaningfully. A direct shot crosses the stage in a second or so. A bouncing one can stay live for four or five, sweeping several clusters.

It creates a resource. A shot with bounces remaining is a shot that can still do something. Players start thinking about bounce economy, which is another dimension to a decision that is otherwise just angle and power.

The limit exists because an unlimited-bounce shot would eventually clear the board on its own, which would remove the decision entirely. Three is enough to make corner routes viable and few enough that they have to be planned.

A combo rule that fits

The combo rule in this game is unlike every other game on the site, and it is the piece that ties the design together.

The streak builds within a shot and resets when the shot ends.

The consequence is large. Twenty gems collected in one flight go 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4 on the multiplier — a substantial total. The same twenty gems spread across four shots never leave a two-times multiplier, and are worth roughly a third as much.

So the scoring says the same thing as the shot economy: find the line that does everything. One great shot beats three adequate ones, and both the multiplier and the 120-point bonus per unused shot push in that direction.

That alignment between two separate systems is what makes the game feel coherent. There is no tension between playing for score and playing efficiently.

Aiming well

Five practical habits.

Read the arc before committing. It is accurate. If it misses on screen, it will miss in flight.

Look for two-cluster lines. The whole game. A shot that threads one cluster is fine; a shot that threads one, bounces off a wall and clips a second is the difference between a good stage and a great one.

Match angle to intent. Low angle and high power for flat sweeps across the stage. High angle and low power to drop into a cluster from above. Those two shapes cover most situations.

Plan the bounce, do not hope for it. A bounce is part of the arc and is drawn in the prediction. Use it deliberately.

Save shots. Each unused shot at the stage clear is worth 120 points, which is more than three plain gems. A stage cleared in three shots is worth substantially more than the same stage cleared in six.

If the planning appeals, the other two physics games on the site are the continuous versions of the same instinct: Rolling Gem Quest asks you to plan a route and carry momentum through it, and Gravity Crystal Hunt asks you to plan an arc and commit to it with no steering afterwards.

Frequently asked questions