Humble Bundle has laid off 12 people — about 20 percent of its staff — in a move that the company's CEO admitted reflected overly eager expansion.

The cuts affected various departments and took place late last week, according to a source who preferred to remain anonymous. Job losses hit people in creative, engineering, business development and communications departments.

"Unfortunately, last week Humble Bundle was forced to let go of some of our employees," confirmed co-founder John Graham, in an email to Polygon. "Despite strong revenue, and our community surpassing $65 million raised for charity to date, our past hiring was too ambitious and we had to make a hard call last week."

Humble Bundle is a game store which sends a proportion of its income to charity. Humble Bundles allow buyers to choose what they pay and how much of their payment goes to charity, to the developers and to Humble Bundle itself. The current Humble Indie Bundle 15 cuts $3.75 to Humble Bundle as a default "tip" on a $25 purchase.

Humble Indie Bundle 15 has so far sold 137,000 units, with less than a day to go before the offer's expiry. The last two bundles both sold more than 160,000 copies, according to a list on Wikipedia. Sales of the Indie Bundle have been diminishing. Humble Indie Bundle 9, released in September, 2013, sold 713,000 bundles. Indie Bundles have generally sold more than 300,000 copies each, stretching back to the earliest days of the packages, in 2011.

Humble Bundle — based in San Francisco, California — recently launched a game subscription service, costing $12 a month.