Some exercises beyond squats to target legs: https://en.wikipedia.org/wiki/Burpee_(exercise) https://en.wikipedia.org/wiki/Burpee_(exercise) lists a number of

Some exercises beyond squats to target legs: https://en.wikipedia.org/wiki/Burpee_(exercise) https://en.wikipedia.org/wiki/Burpee_(exercise) lists a number of interesting variants, if you have the space at home for them. https://en.wikipedia.org/wiki/Calisthenics https://en.wikipedia.org/wiki/Calisthenics has some more ideas that might be amenable to the half hour time window. They require little or no equipment and you could make your routine more interesting by doing some of them outdoors when weather allows.