Terrarium

Terrarium is a small, complete world under glass, lit by a desk lamp in a dark room. There are two cases to keep. The Valley has craggy peaks with forest climbing their slopes, a wide stepped waterfall, and a blue stream winding across the meadow to a turquoise lake, with oaks, blossom, a cabin and a jetty. The High Tarn is a cold alpine cirque: snowfields on the peaks, scree, pines and a dark tarn above the treeline, with short summers and no herons. Each case lives on its own.

Everything in it is alive. Wildflowers, hazel, birch, pine, oak and wild cherry seed, compete for light and water, die back and spread. Roe deer and rabbits graze, mallards dabble, foxes hunt at dusk, trout rise, bees and butterflies work the flowers and fireflies light summer nights. Rabbits keep warrens to sleep in and to bolt into. Every animal has a name, needs and a life story you can read, day by day.

Make the case rich enough and new species come, in stages: a wood mouse is spotted at the vent, a second joins it, and a pair that stays and breeds has settled. Tawny owls follow the mice and roost in the old pines; grey herons wade the shallows for trout and frogs; frogs spawn in spring and their tadpoles climb out as froglets. A swarm of honeybees moves into the skep by the cabin once the meadow is in flower, and pollinates it.

The water is real: rain soaks into the soil, runs off down the slopes into the stream and fills the lake; droughts lower it. In winter snow settles on the peaks and the meadow, the lake freezes from the edges in, frogs sleep in the mud and the herons fly south.

You tend the place, you don't control it:

• Hand: drag a cloud over dry grass to make it rain, or pick up an animal and set it down elsewhere.
• Seeds: sow the plants where they can grow.
• Arrival: ring the glass bell to bring in any species that has settled.
• Lightning: strike dry grass, watch the fire spread, burn out and the meadow grow back.
• Magnifier: follow one creature; the leaves part and its journal fills as it lives.