Glass is the follow-up to Splash! with similar gameplay. Aliens once attacked Earth and now the humans travel to their planets to take the fight to their worlds. One of two players, working together, control a space ship in fixed-screen stages filled with blocks. To win a stage all blocks need to be removed and this done by moving over them. Meanwhile aliens spawn from different directions and roam around. Some of them can also fire while other have special abilities such as leaving behind bombs or restoring the blocks. The player's space ship can shoot bullets (now an unlimited amount unlike in Splash!), but not all enemies can be defeated. It is also possible to leave behind dynamite as a bomb or active a shield for temporary invincibility. Defeated opponents drop coins for extra points, additional bombs, a new primary weapon or energy to restore the shield. The ship can be steered in eight directions and a single credit provides three lives. There is also a time limit per level. The game contains eight worlds with four stages each. The last stage is always a boss fight against a strong character and there are no blocks to clear. In addition the player is rewarded with a nude or revealing picture of a man or a woman. The picture is already teased after completing the first three levels, but with some black blocks covering parts. Only when the boss is defeated is the picture revealed in full. At the start of the game the player chooses between Boys mode or Girls mode to determine the gender of the people in the pictures.