diff --git a/.travis.yml b/.travis.yml
index 707e65ebdf..11343bf677 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,17 +1,19 @@
 language: rust
 rust:
+  - 1.15.0
+  - 1.22.0
+  - 1.26.0
   - stable
   - beta
   - nightly
 matrix:
   include:
-    - rust: 1.8.0
-      before_script:
-        # rand 0.3.22 started depending on rand 0.4, which requires rustc 1.15
-        # manually hacking the lockfile due to the limitations of cargo#2773
-        - cargo generate-lockfile
-        - sed -i -e 's/"rand 0.[34].[0-9]\+/"rand 0.3.20/' Cargo.lock
-        - sed -i -e '/^name = "rand"/,/^$/s/version = "0.3.[0-9]\+"/version = "0.3.20"/' Cargo.lock
+    # try a target that doesn't have std at all
+    - rust: stable
+      env: TARGET=thumbv6m-none-eabi
+      script:
+        - rustup target add $TARGET
+        - cargo build --verbose --target $TARGET --no-default-features
 sudo: false
 script:
   - cargo build --verbose
diff --git a/Cargo.toml b/Cargo.toml
index b75e5449d6..62531353e4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,54 +4,76 @@ description = "A collection of numeric types and traits for Rust, including bigi
 documentation = "https://docs.rs/num"
 homepage = "https://github.com/rust-num/num"
 keywords = ["mathematics", "numerics", "bignum"]
-categories = [ "algorithms", "data-structures", "science" ]
+categories = [ "algorithms", "data-structures", "science", "no-std" ]
 license = "MIT/Apache-2.0"
 repository = "https://github.com/rust-num/num"
 name = "num"
-version = "0.1.42"
+version = "0.2.0"
 readme = "README.md"
 
+[package.metadata.docs.rs]
+features = ["std", "serde", "rand"]
+
 [badges]
 travis-ci = { repository = "rust-num/num" }
 
 [dependencies]
 
 [dependencies.num-bigint]
-optional = true
-version = "0.1.42"
+optional = true # needs std
+version = "0.2.0"
+default-features = false
 
 [dependencies.num-complex]
-optional = true
-version = "0.1.42"
+version = "0.2.0"
+default-features = false
 
 [dependencies.num-integer]
-version = "0.1.36"
+version = "0.1.39"
+default-features = false
 
 [dependencies.num-iter]
-version = "0.1.35"
+version = "0.1.37"
+default-features = false
 
 [dependencies.num-rational]
-optional = true
-version = "0.1.42"
+version = "0.2.1"
+default-features = false
 
 [dependencies.num-traits]
-version = "0.2.0"
+version = "0.2.5"
+default-features = false
 
 [dev-dependencies]
 
 [features]
-bigint = ["num-bigint"]
-complex = ["num-complex"]
-rational = ["num-rational"]
-default = ["bigint", "complex", "rational", "rustc-serialize"]
+default = ["std"]
+
+std = [
+  "num-bigint/std",
+  "num-complex/std",
+  "num-integer/std",
+  "num-iter/std",
+  "num-rational/std", "num-rational/bigint",
+  "num-traits/std",
+]
+
+i128 = [
+  "num-bigint/i128",
+  "num-complex/i128",
+  "num-integer/i128",
+  "num-iter/i128",
+  "num-rational/i128",
+  "num-traits/i128",
+]
+
+rand = [
+  "num-bigint/rand",
+  "num-complex/rand",
+]
 
 serde = [
   "num-bigint/serde",
   "num-complex/serde",
-  "num-rational/serde"
-]
-rustc-serialize = [
-  "num-bigint/rustc-serialize",
-  "num-complex/rustc-serialize",
-  "num-rational/rustc-serialize"
+  "num-rational/serde",
 ]
diff --git a/README.md b/README.md
index eaac524834..efd7b53468 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![crate](https://img.shields.io/crates/v/num.svg)](https://crates.io/crates/num)
 [![documentation](https://docs.rs/num/badge.svg)](https://docs.rs/num)
-![minimum rustc 1.8](https://img.shields.io/badge/rustc-1.8+-red.svg)
+![minimum rustc 1.15](https://img.shields.io/badge/rustc-1.15+-red.svg)
 [![Travis status](https://travis-ci.org/rust-num/num.svg?branch=master)](https://travis-ci.org/rust-num/num)
 
 A collection of numeric types and traits for Rust.
@@ -13,28 +13,18 @@ and generic range iterators.
 
 `num` is a meta-crate, re-exporting items from these sub-crates:
 
-- [`num-bigint`](https://github.com/rust-num/num-bigint)
-  [![crate](https://img.shields.io/crates/v/num-bigint.svg)](https://crates.io/crates/num-bigint)
+| Repository | Crate | Documentation |
+| ---------- | ----- | ------------- |
+| [`num-bigint`]   | [![crate][bigint-cb]][bigint-c]     | [![documentation][bigint-db]][bigint-d]
+| [`num-complex`]  | [![crate][complex-cb]][complex-c]   | [![documentation][complex-db]][complex-d]
+| [`num-integer`]  | [![crate][integer-cb]][integer-c]   | [![documentation][integer-db]][integer-d]
+| [`num-iter`]     | [![crate][iter-cb]][iter-c]         | [![documentation][iter-db]][iter-d]
+| [`num-rational`] | [![crate][rational-cb]][rational-c] | [![documentation][rational-db]][rational-d]
+| [`num-traits`]   | [![crate][traits-cb]][traits-c]     | [![documentation][traits-db]][traits-d]
+| ([`num-derive`]) | [![crate][derive-cb]][derive-c]     | [![documentation][derive-db]][derive-d]
 
-- [`num-complex`](https://github.com/rust-num/num-complex)
-  [![crate](https://img.shields.io/crates/v/num-complex.svg)](https://crates.io/crates/num-complex)
-
-- [`num-integer`](https://github.com/rust-num/num-integer)
-  [![crate](https://img.shields.io/crates/v/num-integer.svg)](https://crates.io/crates/num-integer)
-
-- [`num-iter`](https://github.com/rust-num/num-iter)
-  [![crate](https://img.shields.io/crates/v/num-iter.svg)](https://crates.io/crates/num-iter)
-
-- [`num-rational`](https://github.com/rust-num/num-rational)
-  [![crate](https://img.shields.io/crates/v/num-rational.svg)](https://crates.io/crates/num-rational)
-
-- [`num-traits`](https://github.com/rust-num/num-traits)
-  [![crate](https://img.shields.io/crates/v/num-traits.svg)](https://crates.io/crates/num-traits)
-
-There is also a `proc-macro` crate for deriving some numeric traits:
-
-- [`num-derive`](https://github.com/rust-num/num-derive)
-  [![crate](https://img.shields.io/crates/v/num-derive.svg)](https://crates.io/crates/num-derive)
+Note: `num-derive` is listed here for reference, but it's not directly included
+in `num`.  This is a `proc-macro` crate for deriving some of `num`'s traits.
 
 ## Usage
 
@@ -42,7 +32,7 @@ Add this to your `Cargo.toml`:
 
 ```toml
 [dependencies]
-num = "0.1"
+num = "0.2"
 ```
 
 and this to your crate root:
@@ -51,11 +41,84 @@ and this to your crate root:
 extern crate num;
 ```
 
+## Features
+
+This crate can be used without the standard library (`#![no_std]`) by disabling
+the default `std` feature. Use this in `Cargo.toml`:
+
+```toml
+[dependencies.num]
+version = "0.2"
+default-features = false
+```
+
+The `num-bigint` crate is only available when `std` is enabled, and the other
+sub-crates may have limited functionality when used without `std`.
+
+Implementations for `i128` and `u128` are only available with Rust 1.26 and
+later.  The build script automatically detects this, but you can make it
+mandatory by enabling the `i128` crate feature.
+
+The `rand` feature enables randomization traits in `num-bigint` and
+`num-complex`.
+
+The `serde` feature enables serialization for types in `num-bigint`,
+`num-complex`, and `num-rational`.
+
+The `num` meta-crate no longer supports features to toggle the inclusion of
+the individual sub-crates.  If you need such control, you are recommended to
+directly depend on your required crates instead.
+
 ## Releases
 
 Release notes are available in [RELEASES.md](RELEASES.md).
 
 ## Compatibility
 
-Most of the `num` crates are tested for rustc 1.8 and greater.
-The exception is `num-derive` which requires at least rustc 1.15.
+The `num` crate as a whole is tested for rustc 1.15 and greater.
+
+The `num-traits`, `num-integer`, and `num-iter` crates are individually tested
+for rustc 1.8 and greater, if you require such older compatibility.
+
+
+[`num-bigint`]: https://github.com/rust-num/num-bigint
+[bigint-c]: https://crates.io/crates/num-bigint
+[bigint-cb]: https://img.shields.io/crates/v/num-bigint.svg
+[bigint-d]: https://docs.rs/num-bigint/
+[bigint-db]: https://docs.rs/num-bigint/badge.svg
+
+[`num-complex`]: https://github.com/rust-num/num-complex
+[complex-c]: https://crates.io/crates/num-complex
+[complex-cb]: https://img.shields.io/crates/v/num-complex.svg
+[complex-d]: https://docs.rs/num-complex/
+[complex-db]: https://docs.rs/num-complex/badge.svg
+
+[`num-derive`]: https://github.com/rust-num/num-derive
+[derive-c]: https://crates.io/crates/num-derive
+[derive-cb]: https://img.shields.io/crates/v/num-derive.svg
+[derive-d]: https://docs.rs/num-derive/
+[derive-db]: https://docs.rs/num-derive/badge.svg
+
+[`num-integer`]: https://github.com/rust-num/num-integer
+[integer-c]: https://crates.io/crates/num-integer
+[integer-cb]: https://img.shields.io/crates/v/num-integer.svg
+[integer-d]: https://docs.rs/num-integer/
+[integer-db]: https://docs.rs/num-integer/badge.svg
+
+[`num-iter`]: https://github.com/rust-num/num-iter
+[iter-c]: https://crates.io/crates/num-iter
+[iter-cb]: https://img.shields.io/crates/v/num-iter.svg
+[iter-d]: https://docs.rs/num-iter/
+[iter-db]: https://docs.rs/num-iter/badge.svg
+
+[`num-rational`]: https://github.com/rust-num/num-rational
+[rational-c]: https://crates.io/crates/num-rational
+[rational-cb]: https://img.shields.io/crates/v/num-rational.svg
+[rational-d]: https://docs.rs/num-rational/
+[rational-db]: https://docs.rs/num-rational/badge.svg
+
+[`num-traits`]: https://github.com/rust-num/num-traits
+[traits-c]: https://crates.io/crates/num-traits
+[traits-cb]: https://img.shields.io/crates/v/num-traits.svg
+[traits-d]: https://docs.rs/num-traits/
+[traits-db]: https://docs.rs/num-traits/badge.svg
diff --git a/RELEASES.md b/RELEASES.md
index cb55431a36..cf968c79bd 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,4 +1,46 @@
-# Release 0.1.42
+# Release 0.2.0 (2018-06-29)
+
+All items exported from `num-integer`, `num-iter`, and `num-traits` are still
+semver-compatible with those exported by `num` 0.1.  If you have these as public
+dependencies in your own crates, it is not a breaking change to move to `num`
+0.2.  However, this is not true of `num-bigint`, `num-complex`, or
+`num-rational`, as those exported items are distinct in this release.
+
+A few common changes are listed below, but most of the development happens in
+the individual sub-crates.  Please consult their release notes for more details
+about recent changes:
+[`num-bigint`](https://github.com/rust-num/num-bigint/blob/master/RELEASES.md),
+[`num-complex`](https://github.com/rust-num/num-complex/blob/master/RELEASES.md),
+[`num-integer`](https://github.com/rust-num/num-integer/blob/master/RELEASES.md),
+[`num-iter`](https://github.com/rust-num/num-iter/blob/master/RELEASES.md),
+[`num-rational`](https://github.com/rust-num/num-rational/blob/master/RELEASES.md),
+and [`num-traits`](https://github.com/rust-num/num-traits/blob/master/RELEASES.md).
+
+### Enhancements
+
+- Updates to `num-integer`, `num-iter`, and `num-traits` are still compatible
+  with `num` 0.1.
+- 128-bit integers are supported with Rust 1.26 and later.
+- `BigInt`, `BigUint`, `Complex`, and `Ratio` all implement `Sum` and `Product`.
+
+### Breaking Changes
+
+- `num` now requires rustc 1.15 or greater.
+- `num-bigint`, `num-complex`, and `num-rational` have all been updated to 0.2.
+- It's no longer possible to toggle individual `num-*` sub-crates using cargo
+  features.  If you need that control, please use those crates directly.
+- There is now a `std` feature, enabled by default, along with the implication
+  that building *without* this feature makes this a `#![no_std]` crate.
+  `num::bigint` is not available without `std`, and the other sub-crates may
+  have limited functionality.
+- The `serde` dependency has been updated to 1.0, still disabled by default.
+  The `rustc-serialize` crate is no longer supported by `num`.
+- The `rand` dependency has been updated to 0.5, now disabled by default.  This
+  requires rustc 1.22 or greater for `rand`'s own requirement.
+
+**Contributors**: @CAD97, @cuviper, and the many sub-crate contributors!
+
+# Release 0.1.42 (2018-02-08)
 
 - [All of the num sub-crates now have their own source repositories][num-356].
 - Updated num sub-crates to their latest versions.
diff --git a/ci/rustup.sh b/ci/rustup.sh
index 31e5290a45..c5aea794b5 100755
--- a/ci/rustup.sh
+++ b/ci/rustup.sh
@@ -1,19 +1,12 @@
 #!/bin/sh
 # Use rustup to locally run the same suite of tests as .travis.yml.
-# (You should first install/update 1.8.0, stable, beta, and nightly.)
+# (You should first install/update all versions listed below.)
 
 set -ex
 
 export TRAVIS_RUST_VERSION
-for TRAVIS_RUST_VERSION in 1.8.0 stable beta nightly; do
+for TRAVIS_RUST_VERSION in 1.15.0 1.22.0 1.26.0 stable beta nightly; do
     run="rustup run $TRAVIS_RUST_VERSION"
-    if [ "$TRAVIS_RUST_VERSION" = 1.8.0 ]; then
-      # rand 0.3.22 started depending on rand 0.4, which requires rustc 1.15
-      # manually hacking the lockfile due to the limitations of cargo#2773
-      $run cargo generate-lockfile
-      $run sed -i -e 's/"rand 0.[34].[0-9]\+/"rand 0.3.20/' Cargo.lock
-      $run sed -i -e '/^name = "rand"/,/^$/s/version = "0.3.[0-9]\+"/version = "0.3.20"/' Cargo.lock
-    fi
     $run cargo build --verbose
     $run $PWD/ci/test_full.sh
 done
diff --git a/ci/test_full.sh b/ci/test_full.sh
index 661b172330..e462b453bd 100755
--- a/ci/test_full.sh
+++ b/ci/test_full.sh
@@ -4,6 +4,14 @@ set -ex
 
 echo Testing num on rustc ${TRAVIS_RUST_VERSION}
 
+FEATURES="serde"
+if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta|stable|1.26.0|1.22.0)$ ]]; then
+  FEATURES="$FEATURES rand"
+fi
+if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta|stable|1.26.0)$ ]]; then
+  FEATURES="$FEATURES i128"
+fi
+
 # num should build and test everywhere.
 cargo build --verbose
 cargo test --verbose
@@ -13,11 +21,12 @@ cargo build --no-default-features
 cargo test --no-default-features
 
 # Each isolated feature should also work everywhere.
-for feature in bigint complex rational rustc-serialize serde; do
-  cargo build --verbose --no-default-features --features="$feature"
-  cargo test --verbose --no-default-features --features="$feature"
+# (but still with "std", else bigint breaks)
+for feature in $FEATURES; do
+  cargo build --verbose --no-default-features --features="std $feature"
+  cargo test --verbose --no-default-features --features="std $feature"
 done
 
-# Downgrade serde and build test the 0.7.0 channel as well
-cargo update -p serde --precise 0.7.0
-cargo build --verbose --features "serde"
+# test all supported features together
+cargo build --features="std $FEATURES"
+cargo test --features="std $FEATURES"
diff --git a/src/lib.rs b/src/lib.rs
index 03156ffcbc..8a37c5392c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -21,7 +21,7 @@
 //!
 //! ```
 //! extern crate num;
-//! # #[cfg(all(feature = "bigint", feature="rational"))]
+//! # #[cfg(feature = "std")]
 //! # mod test {
 //!
 //! use num::FromPrimitive;
@@ -41,7 +41,7 @@
 //!     approx
 //! }
 //! # }
-//! # #[cfg(not(all(feature = "bigint", feature="rational")))]
+//! # #[cfg(not(feature = "std"))]
 //! # mod test { pub fn approx_sqrt(n: u64, _: usize) -> u64 { n } }
 //! # use test::approx_sqrt;
 //!
@@ -55,42 +55,45 @@
 //!
 //! ## Compatibility
 //!
-//! The `num` crate is tested for rustc 1.8 and greater.
+//! The `num` crate is tested for rustc 1.15 and greater.
 
-#![doc(html_root_url = "https://docs.rs/num/0.1")]
+#![doc(html_root_url = "https://docs.rs/num/0.2")]
+#![no_std]
 
-extern crate num_traits;
+#[cfg(feature = "std")]
+extern crate num_bigint;
+extern crate num_complex;
 extern crate num_integer;
 extern crate num_iter;
-#[cfg(feature = "num-complex")]
-extern crate num_complex;
-#[cfg(feature = "num-bigint")]
-extern crate num_bigint;
-#[cfg(feature = "num-rational")]
 extern crate num_rational;
+extern crate num_traits;
 
-#[cfg(feature = "num-bigint")]
+#[cfg(feature = "std")]
 pub use num_bigint::{BigInt, BigUint};
-#[cfg(feature = "num-rational")]
+
+pub use num_complex::Complex;
+
 pub use num_rational::Rational;
-#[cfg(all(feature = "num-rational", feature="num-bigint"))]
+#[cfg(feature = "std")]
 pub use num_rational::BigRational;
-#[cfg(feature = "num-complex")]
-pub use num_complex::Complex;
+
 pub use num_integer::Integer;
+
 pub use num_iter::{range, range_inclusive, range_step, range_step_inclusive};
+
 pub use num_traits::{Num, Zero, One, Signed, Unsigned, Bounded,
                      one, zero, abs, abs_sub, signum,
                      Saturating, CheckedAdd, CheckedSub, CheckedMul, CheckedDiv,
-                     PrimInt, Float, ToPrimitive, FromPrimitive, NumCast, cast,
+                     PrimInt, ToPrimitive, FromPrimitive, NumCast, cast,
                      pow, checked_pow, clamp};
+#[cfg(feature = "std")]
+pub use num_traits::Float;
 
-#[cfg(feature = "num-bigint")]
+#[cfg(feature = "std")]
 pub mod bigint {
     pub use num_bigint::*;
 }
 
-#[cfg(feature = "num-complex")]
 pub mod complex {
     pub use num_complex::*;
 }
@@ -107,7 +110,6 @@ pub mod traits {
     pub use num_traits::*;
 }
 
-#[cfg(feature = "num-rational")]
 pub mod rational {
     pub use num_rational::*;
 }