Press X to "connect" a gamepad.
move : KB cursor, WASD, GP D, sticks
jump : KB up, W, space, GP A, sticks press
climb / swim : KB up, W, GP up, sticks up
use : KB ctrl, E / GP B, R shoulder
drop : KP 0, KB Q , GP Y, L shoulder

SPOILER
Explore the cave and gather seeds from plants to grow useful objects.
A portal allows you to access a new cave.
The portal needs plenty of space, and is only active if it has a switch directly beneath it.
Toggle switches to generate a seed value for the next cave, and place further switches beside the first to generate a wider range of values.