The antonyms for "casts shadow" can be "illuminate" or "brighten." To illuminate means to light up or make something brighter, while to brighten means to make something less dark or more full of light. Both these antonyms signify the opposite of casting shadow or blocking light. For example, a light bulb illuminates a room, making it brighter, while sunlight brightens up a dark alley. The use of these antonyms helps to create a positive and uplifting atmosphere, emphasizing light and positivity rather than darkness and shadows. Therefore, when looking for alternatives to "casts shadow," consider using "illuminate" or "brighten" to convey a more positive and bright light.