The basic idea of TenBlocks is:
There are two types of blocks you can fill in: 2 times 5, which you do by dragging out a rectangle in the required position with the mouse, and 3 times 3 with an extra 1, which you do by dragging out a 3 times 4 rectangle. To delete a rectangle that you have placed, click on it to select it, and then press delete or backspace, or click on the "Remove Block" button. When you have filled in as many blocks of ten as possible, i.e. there are less than ten squares not filled in, you have finished that problem (as shown by a change of colour), and you can select the next one to do. Keep going until you have done them all.
TenBlocks is open source, and the source is available from http://github.com/pdorrell/tenblocks.
Copyright © 1999-2008 Philip Dorrell (email) TenBlocks is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License version 3 as published by the Free Software Foundation. TenBlocks is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.
Warning: unfortunately the original source code was lost due to computer crashes and errors in backup scripting, so the current source has been reconstructed by decompilation, and some of the variable names are not very meaningful.