Capturing a star's energy
The sunlight that hits one planet is already a thin slice of what the star puts out. The long job is to collect more of the rest.
The star is already producing the power
A star like the Sun radiates on the order of 4 × 10^26 watts. That energy leaves in every direction. A planet intercepts only the part that happens to hit its disk. For Earth, that incoming sunlight is on the order of 1.7 × 10^17 watts at the top of the atmosphere, before clouds, night, and atmosphere take their share.
Those two numbers are the whole argument for thinking at stellar scale. Even if a planet used all the sunlight that reaches it, it would still be using a tiny fraction of the star. A Type II civilization is one that has gone after a much larger fraction of the total.
This is physics, not a construction plan. Knowing that the energy is there does not tell you how to collect it, how to send it where it is needed, or how long the work would take.
A swarm, built a piece at a time
The workable picture is a large number of collectors in independent orbits, not a single rigid shell. A solid shell around a star would have to be held in place against instabilities. A swarm does not have that problem in the same way. Each collector is a spacecraft or a station with a job: intercept light, convert it, and pass the energy on.
Because the pieces are independent, the swarm can grow gradually. The first collectors would be valuable on their own, long before they formed anything you would call a complete enclosure. Completeness is not required for the idea to matter. Coverage is a sliding measure. A thin swarm is already a step toward Type II. A thick one is a later step.
The materials would have to come from somewhere. A planet is a poor mine if you intend to build at the scale of a star, both because of the mass you would have to lift and because of the damage you would do by taking it. The more natural sources are small bodies already in space: asteroids, moons, and the leftovers of planet formation. That is one reason launch, mining, and robotics sit inside the same story. Why reaching orbit still matters and Robot Motion take up parts of that work.
Conversion, not just collection
Sunlight on a collector is not yet a factory, a habitat, or a computer. You still have to turn it into electricity or process heat, and you have to move that energy, sometimes across long distances. You also have to handle the heat you do not use. Every conversion step wastes some energy as heat, and at high power that waste is itself an engineering problem.
There is also the question of use. A civilization would not collect a star's output for the sake of a higher type number. It would collect it to run industry, computation, life-support, and further construction. The type number is a shadow of those uses. Sentient Cloud is about the computing side of that demand. Computation at a large scale is an energy load, not an abstraction.
No honest timetable
It would be easy to dress this up as a century-by-century plan. That would be a story, not a forecast we can defend. We do not have a published, engineered design for a star-surrounding swarm, and we do not have a cost or a schedule that would survive contact with the real industrial base.
What we can say is narrower, and more useful. The energy is there. The first steps (better collectors, cheaper access to orbit, machines that can work far from a workshop, and a clearer account of world power) are already real fields of work. The type number on Where humanity sits on the scale shows how far those steps still have to go. The goal is large. The honest next move is to measure, and to build the pieces that would still be worth having even if the swarm stayed thin.
Common questions
Would collectors block a star's light as seen from far away?
A dense enough swarm would intercept light and reradiate some of the energy as heat. Astronomers have discussed that as a possible signature of a very large industrial system. A thin swarm would be much harder to notice. No such civilization has been confirmed.
Could this be done with collectors only on a planet's surface?
Surface collectors can use the sunlight that already hits the planet, and that is already a large resource. They cannot, by themselves, reach Type II, because they never see the light that misses the planet.
Is there a standard design for the collectors?
No. The swarm is a class of ideas, not a finished blueprint. The shared claim is that many independent collectors are more plausible than a single rigid shell.