These controllers can be bought for about ~$10 from Aliexpress which makes it possible to light an entire room with LEDs for about ~$20 if you wish. Controlling them is pretty easy too, besides the available Android application, the protocol is actually fairly simple.

The controller: RGBWW LED Strip Light WiFi Controller Dimmer ESP8266 (Android WLAN Control) 1 Port Control 200 Lights Output 5 Routes PWM Data

Here’s a simple Python script to generate a rainbow: