As Singaporeans mark the nation's bicentennial year by reflecting on how it came into being, Prime Minister Lee Hsien Loong urged them to also "think of how we can move forward together".

Noting that Singapore is always a work in progress, he said at the launch of the Singapore Bicentennial yesterday: "It is every generation's duty to keep on building, for our children, and for our future."

In doing so, Singaporeans not yet born will have, in another 50 or 100 years, a richer and greater Singapore Story to tell. It will be, he added, "one that we will have helped to write together".

The year-long bicentenary, which will feature, among others, projects by artists, schools and ethnic associations, started along the Singapore River to understand where Singapore began, and will close at Marina Bay to look forward into the future.

Following his speech, PM Lee, and political and community leaders saw a visual representation of much of the historical milestones he spoke about, in a multimedia light show, called Bridges Of Time.

Using light, sound, projection and water, and set against the city skyline, it tells the story of a traveller who sails through time and space to reach a mythical island - Singapore. The group then toured the Civic District where projections depicting different nuggets of history were cast onto the facades of neighbouring monuments.

Earlier in his address, the Prime Minister spoke about Singapore's separation from Malaysia, saying that both parting ways in less than two years after the merger was not surprising, in retrospect.

Tracing events since Sir Stamford Raffles established Singapore as a free port, he said: "Over nearly 150 years, our political values, inter-communal relations, and world views had diverged from the society on the other side of the Causeway."

Its identification as South-east Asian and Malayan, seeded in 1819, drove Singapore to join the Federation of Malaysia in 1963, he added.

But as a British colony, Singapore was never governed as part of Malaya and that made "us quite different from our neighbours and friends", said PM Lee.

He also noted that even before the British came, Singapore already had a thriving seaport called Temasek at the mouth of the Singapore River. That was back in the 14th century.

In the 16th and 17th centuries, Europeans who came to South-east Asia knew about the island.

When Raffles arrived in 1819, his establishment of Singapore as a free port was a "crucial turning point in our history", the PM said, as "it set this island on a trajectory leading to where we are today".

The population grew with immigrants, and the streets of Singapore tell of their diverse origins, he noted, citing Malacca Street, Amoy Street, Kadayanallur Street, Bugis Street and Bussorah Street.

"Thus, we became a multicultural and open society," he added.

Trade, the island's lifeblood, linked Singapore to the neighbouring archipelago and the world beyond, and economic and family ties were developed, especially with the Malay peninsula, said PM Lee.

However, Singapore's history since 1819 ensured that it not only survived but also thrived after separation.

PM Lee credited the pioneer generation with having the grit and resolve to show they could be masters of their own fate when Singapore left Malaysia.

The journey, however, was not without triumphs and tragedies.

Paying tribute to the nation's forebears, he said they paid with blood, sweat and tears.

They cleared the jungles, and planted nutmeg, gambier and rubber. Indentured coolies slaved at the quayside. Resourceful traders built import and export businesses, creating prosperity.

In the process, communities were formed to help one another, including Chinese clans, welfare bodies like the Sree Narayana Mission and cultural groups like Angkatan Sasterawan'50.

"Over two centuries, all these different strands wove together into a rich tapestry, a shared sense of identity and eventually, a Singapore identity and nation."

PM Lee said he is glad that more than 200 groups and organisations are holding commemorative events for the bicentenary. "Their stories and journeys are the personal experiences and collective memories that give life and meaning to the Singapore Bicentennial story," he said.