Cooling a laser tube with room-temperature water is generally considered the minimum. Once the coolant warms up when doing long or high-power jobs the laser tube starts to destroy itself. To prolong the lifespan of your tube it should really be cooled with chilled automotive coolant. Off-the-shelf chillers start at about AUD$600, however I discovered that my office was throwing out a stack of chiller units that were used in prototyping liquid cooled electric car charging cables. I filled the boot of my Corolla

Two Aspen chiller units joined in series.

The attiny10 is very tiny, only 1kB of flash and no EEPROM. The code that blinks the LED and the pattern for the blinking must share the same 1kB of space. I wrote some python code to digest a string of text and convert it into an on/off LED sequence. The code running on the microcontroller just needs to wake, read the next bit, set the LED accordingly, then sleep for 100ms.