Quantum Conundrum is on sale at Amazon for 40% off and 33% off at GMG. The discount at GMG gets a little bigger if you have any of the 20% off voucher codes left.
Amazon
– Quantum Conundrum = $8.99 (40% off)
GMG
– Quantum Conundrum = $10.04 (33% off)
– Quantum Conundrum: Season Pass = $13.39 (33% off)