Slide the ball around the grid picking up the gems. Every time the ball moves, it will keep sliding until it either hits a wall, or stops on a stop square (the broken circles). Try to collect every gem without running into any of the mines.
If you hit a mine and explode, you can Undo and continue playing; the game will track how many times you died.
On a touch screen, a tap does what a click does.
Use the numeric keypad to slide the ball horizontally, vertically or diagonally. Alternatively, click on the grid to make the ball move towards where you clicked.
You can also press on the ball itself and drag out the way you want it to go: an arrow on the ball shows the direction, and letting go sends it. Let go on the ball to call the slide off. This works with a finger as well.
The arrow keys slide the ball horizontally and vertically, and the digit keys work like the numeric keypad even without one: 8 is up, 9 up and right, 6 right, and so on round.
Hint shows the next slide rather than simply making it. Nothing in Inertia is forced by logic, so the hint goes for the gem the fewest slides away that the ball can take without leaving any other gem out of reach, and tells you what each slide does on the way.
The thing the hint keeps reminding you of is the rule that catches everyone out: you don’t choose where you stop. A slide that collects says what brings the ball to a halt — a wall, or a stop square. When a slide could grab the outlined gem but would leave the ball somewhere it can never reach other gems from, the hint says so and goes another way. When the ball has only one way to go, because walls block the rest or every other way runs onto a mine, it says that too.
Using the hint is not the same as using Show solution…: only the solution marks the game as auto-solved.
The hint refuses when there is nothing it can do from here: if the ball is dead, or has already left a gem where it can never be reached, it asks you to undo back to a position where it can, and circles the gems it can no longer reach. When every gem can still be reached but no route collects them all, it says that no solution can be found from this position, and circles nothing.
Check & save asks the hint the same thing, and won’t save a position it would ask you to undo from.
These parameters are available from the ‘Custom type…’ option on the ‘Type’ menu.